IT8347727A1 - "Process for the production of dithiazole disulfides". - Google Patents

Description

DESCRIPTION _ 47727^83 attachment to a patent application for an invention _ having as title ;

"Process for the production of dithiazole disulfides" in the name of ; AKZO NV _

SUMMARY

A process for the production of dithiazolyl-( 2? 2<1 >)-disulfides is described.

?r or?

R? -N. N-

Q ai _ c W' \C. <?>R' O Q

in particular of dibenzothiazolyl-( 2, 2<1 >)-disofurans,

<?>p?r o3 in which 2-mercaptothiazoles are converted to the title compounds by oxygen in water as the medium-<? >. <? >?<" >! -C CO

reaction zone and in the presence of ammonia as cata-4

? <~~ ><3 ? lizer and possibly heavy metals. The compounds of the title are used as vulcanizing agents for rubber.

The present invention relates to a process for the production of dithiazolyl-(2? 2') disulfides by oxidation of 2-mercaptothiazoles | j by means of oxygen, in particular of dibenzothiazolyl-disulfide starting from 2-mercaptobenzothiazole. | For the production on a technical scale of dibenzothiazolyl-disulfides by oxidation of 2-o

To date, various oxidation methods have been used for mercaptobenzothiazoles. However, most of the known processes already have the drawback of starting with expensive oxidation agents.

in comparison with oxygen, for example^ chlorate/nir

trite (PlainJInal Report 1018, page 22), nitrite/oxygen (US Patent 1,908 *935) ? nitrite (US Patents

-?! USA 2. 119 - 131 e 3.062*825), chlorine (Kirk-Othmer,__En-C? 23 49_ 314)_ and ^zone ( SU-PS 420 247) . j

Most of the processes indicated in the above-mentioned publications also present further disadvantages, such as the requirement of large quantities of CQ or acids, bases or other auxiliary substances, the formation sometimes of large quantities of by-products or secondary products or complicated reaction conditions.

cate or critical, with the need for careful control (this for example in the case of the use of

chlorine as an oxidizing agent).

Also worth mentioning is a process for the electrolytic oxidation of 2-mercaptobenzothiazo

to dibenzothiazolyl-disulphurum (DOS 27 43 629 ) ?

An attempt has now also been made to carry out the oxidation of 2-mercaptobenzothiazole to dibenzothiazo-?lyl-disulfide with oxygen as the sole oxidizing agent.

According to the process of U.S. Patent 3,654,297, this is possible by using cobalt phthalocyanine sulfate, disulfonate, trisulfonate, or tetrasulfonate or mixtures thereof as catalyst and carrying out the oxidation in an organic solvent containing less than 15% by weight of water at temperatures of 50-80°C. (Compare also U.S. Patent 575-348; Chem. et al.

Abstr . 88 ( 1978 ) ? 89657 g) . The production and industrial use of this catalyst are, however, problematic.

It is also known from DOS 23 55 897 that it is

<?>can carry out the oxidation of 2-mercaptobenzothiazoles to dibenzothiazolyl disulfides using simultaneously oxygen or a gas containing oxygen and ferrous chloride - in particular ferric chloride in a saturated aliphatic alcohol having 1-10 carbon atoms - at temperatures between 0 and 150°C. This catalyst, however, leads to a satisfactory reaction rate only if it is used in large quantities, i.e. in the ratio of 0.8-1.5 moles per mole of 2-mercaptobenzothiazole. The decisive drawback of the procedure, however, is that the iron precipitates during the reaction in the form of basic salts* and the dibenzothiazolyl disulfide obtained is heavily contaminated with iron. A product obtained in this manner cannot, for example, be used as a vulcanizing agent without expensive purification.

An economically interesting process for the catalytic oxidation of 2-mercaptothiazoles by oxygen is finally described in DOS 29 44 225. According to this patent, a mercaptothiazole is reacted by oxygen or an oxygen-containing gas in the presence of organic solvents and tertiary amines as catalyst, possibly also heavy metals or heavy metal compounds as co-catalyst, preferably at temperatures between 20 and 90°C. The dithiazolyl (2, 2 *)-disulfides thus obtained are characterized by a high level of purity and can be used without further purification, for example directly as rubber vulcanizing agents. In comparison with the two processes mentioned above, in which the ! a 2-mercaptobenzothiazole is also induced by oxygen. This process is distinguished by the fact that simple and economical catalysts are used in very large quantities and that these catalysts can be circulated with the mother liquor without their activity decreasing significantly.

A supplementary patent application (Pr. No. 31 1 3 298 7) to the above-mentioned German patent application P 29 44 225*9 describes the production of dithiazolyl-(2? 2' )-disulfides with ammonia instead of tertiary amines as catalyst.

In all these processes for the oxidation of 2-mercaptobenzothiazole to dibenzothiazolyl disulfide with oxygen as the sole oxidizing agent according to U.S. Patent No. 3,654,297, DOS 23,55, and DOS 29,44,225 (as well as Complementary Application No. P 31,13,298,7) organic solvents are considered necessary as solvents. On the contrary, water as a solvent has appeared completely unsuitable. <k| >K<[ >m<zj* S>f?<G>t<uipu *..1E.>.<. >-<.>

Thus, for example, according to US patent 3*654*297 it is not recommended to use a solvent with more than 15 io of water by weight. Furthermore, DOS 29 44 <'>225 (see page 16, lines 23-27) recommends:

I

Do not let the proportion of water in the solvent rise above 10% by weight. Further tests are needed.

according to the DOS 29 44 225 procedure they indicated that with water as the only solvent it does not occur

no conversion of 2-mercaptobenzothiazole to dibenzothiazolyl-( 2, 2 <1 >)-disulfide. For example, if examples 18, 24 and 23 are performed, as given in DOS 29 _4 ^ 22J5?

in water instead of the solvents indicated therein, appeared

under other conditions, no oxidation occurs,

as shown in Table 1.

TABLE 1:

ex. Tests for the oxidation of 2-mercaptobenzothiazole (?.???) - -?4_ to dibenzo t iazolyl-disulfide (MBTS) ?

Reaction conditions: 60 mmol MBT, 108 mmol thiamine, at room temperature

reaction 70?0, pressure

of 0 ss i g e_no 20 bar , d urans e

of the reaction 6, 5 hours.

Solvent _ Catalyst _ Conversion Yield of 120 g of copper by MBT| $ MBTS <fo 0.02 mmol_ <?>

_ <D0S 29 44 225 isopropa-. _ acetate ra^- _ 82.7 80.5 _ -jEs. 18 freight

- ? i 0S 29 44 225- toluene - - -acetate ra - 90, 6-- 88.6 .

jEs. 24 meico

_ [ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ __ _

Comparison test: water and cupric acetate 0 ___

DOS 29 44 225

? Ex. 28 - isopropa- - cupric oleate - - 82.0 ? 80, 2

| rent

.Test with- water . cupric oleate 0

Ready _ _

_ Finally there should be a preconception about

against the use of water as a solvent in the process

:

according to the supplementary patent application No. P 31 13 298.7 since it was known that ammonia as well as primary and secondary amines are oxidized in aqueous solution, unlike tertiary amines, by oxygen in the presence of metal catalysts. For example, it could be deduced from the section entitled "Chemisches Verhalten des Ammonium-

" . Il / ^ lons und des Ammoniaks in wassriger Lo sung"_( "Chemical behavior of the ammonium ion and of ammonia in aqueous solution") in "Gmelins Handbuch der anorganischen Chemie", eighth edition, Vol. 23> pages j

12 and following (the behavior towards oxygen in the presence of metals or metal ions is mentioned in detail on page 13, _r ' ig <~>a 21_up to <. >a a ? page 15, line 4, taking particular account of copper.) that ammonia is catalytically oxidized to nitrite in aqueous solution. _ _ <i& >^<ll sA?OM?O?DJjKpGAH SRZ & B>.<.>.

Particularly for reasons of economy and safety, there was now a need;

to have a process for the production of dithiazolyl-( 2? 2' )-disulfides by oxidation of

2-mercaptobenzothiazoles by oxygen, which pos

can be performed not in organic solvents, but in the cheaper solvent water? harmless and favorable for

the environment.

The object of the present invention is?

to make an economic process available;

for the production of dithiazolyl-(2? 2<1 >)-disulfides by oxidation of 2-mercaptothiazoles by oxygen in the presence of water as solvent.

It has now been surprisingly found that under suitable reaction conditions the oxidation of 2-mercaptothiazoles to dithiazolyl-(2? 2<1 >)-disulfides by oxygen can also be carried out successfully in water as solvent if ammonia and possibly a heavy metal derivative as catalyst are used (cf. German patent application No. P 31 13 298.7). In the case of the oxidation of 2-mercaptobenzothiazole, a

This way dibenzothiazolyl-(2? 2')-disulfide of high purity with good yields (up to 99$) and high

selectivity (up to over $99). Secondary actions

which were to be expected based on the indications in the literature (oxidation of ammonia or formation

of sulfenamide (compare DOS 2349934? page 5?

jrighe 22-24)) have not been observed at this pr?-?

j

jposito.

The problem was solved by a pro

yield for the production of dithiazolyl-(2,2')-disulfides of the general formula

R - C - N N - C - R

// (I)

\

R?- C - S S - C - R

?

where R and R' can be the same or different and represent respectively a hydrogen atom? a halogen atom? a nitro group? a hydroxyl group or an organic radical possibly substituted once or more such as an alkyl or alkoxy radical having 1-6 carbon atoms or a cycloalkyl or aryl radical having 6-12 carbon atoms? the substituents can be each time a halogen atom, a nitro group, a hydroxyl group or an alkyl or alkoxy radical having 1-5 carbon atoms, or where R and R <1 >^ jointly form the radical:

1I1

to the )

quarrels

R" I.I

where R" , R" ' , R'*" , R<f>'" ? can be equal or different? ^ have _ respectively 11 the same_meaning?

to as R and ^by catalytic oxidation of

a_ 2- m er chapter of the general formula J _

R - C - N

\ - SH co (III)

/

R'- C - S oai f?r where R and R<1 >have the meaning indicated above,

"*I by oxygen or a gas containing oxygen m a

solvent in the presence of a catalyst and possibly a heavy metal co-catalyst at temperatures in the range of Q-150?C, characterized by !

the fact of using water as a solvent and as a catalyst

ammonia remover.

In general, the amount of water corresponds to 1.5-12 times the weight of 2-mercaptothiazole used. Larger amounts of water should be avoided.

economic reasons

In many cases it can be advantageous to use water as the reaction medium with the addition of water-soluble organic solvents (for example alcohols).

The amount of ammonia can be varied over a wide range; preferably one im-|

.

i i

[however fold ammonia in quantities of about 0.5-25fi

i

{

by weight, based on the reaction mixture.

_ The substituents from R to R<,,,M>. of general formulas I? II and III are preferably a chlorine or bromine atom? a hydroxyl group? a nitro group? a straight-chain or branched-chain alkyl radical having 1-4 carbon atoms, such as a methyl radical? ethyl radical? propyl radical? tert-propyl radical? butyl radical? an alkoxy radical having

to 1-4 carbon atoms as a methoxy radical ? -?s ? O

ethoxylic ?_propoxylicq p butoxylic or a ra-<?>CV O

diphenyl? tolyl, ethyl phenyl? nitrophenyl:

lic? phenyl chloro? phenyl or naphthyl bromine._ -J - ? ? dithiazolyl-(2? 2*)-disulfides_are used as vulcanizing agents., of rubber. <<?>-?-O

_ _ ?The process according to the present invention is particularly significant for the production of dibenzothiazolyl-(2? 2' )-disodium, the most important representative of this class of compounds. _

And <1 >however suitable .with equal success_ in the production

of further compounds of this type. For the preferred production of dibenzothiazolyl-(2? 2<1 >)-disulfide the J

2-Mercaptobenzothiazole is used as a starting material. Examples of other mercaptothiazoles that are suitable as starting materials for the production

?

of further dithiazolyl-(2? 2<1 >)~disulfides of the formup

i

the general I? are among others the following compounds:]

2-mer captothiazole

2-mercapto-4-methylthiazole

2-mercapto-4-ethylthiazole '?

2-mercapto-4-n-propylthiazole

2-mercapto-4? 5-dimethylthiazole.

2-mer cap to-4, 5-di-n-but the thiazole

2-mer capto-4-phenylthiazole

2-mer capto-5-chloro-4-phenylthiazole

2-mer capto-4-p-bromophenyl-thiazole?.

<? >-< | 2-mer cap to-4-m-nitrophenylthiazole

<?>?? 2-mer cap to-4-m- chloro phenylthiazole

. . 2-mercapto-4-methylbenzo thiazole

2-mercs.pto-5-me tilbenzo thiazole

- ^ 2-me r capto- 4> 5- dime tilbenzo thiazole

2-mer capto-4-f enylbenzo thiazole V

? 2-iner cap to-4-methoxybenzo thiazole

2-mer capto-6-methoxybenzo thiazole

2-mer capto- 5 > 6- dime to ss ibenzo thiazole

?

2-mer cap to-6-methos si- 4-nitrobenzo thiazole

2-mercapto-6-ethoxybenzothiazole

2-mer cap to-4-chlorobenzo thiazole

2-mer capto- 5- there? robenz? thiazole

| 2-mercapto-6-cbrobenzothiazole

i

| 2-mercapto-7-chlorobenzothiazole

i

! 2-mercapto-5-chloro-6-methoxybenzo thiazole

i

i i

i

_ 2-mercapto-5-chloro-4-nitrobenzothiazole

_ _2-mercapto-5-chloro-6-nitrobenzo thiazole

_ _ _2-mercapto-4?_5-dichlorobenzo thiazole

2-mercapto-4? 7~dichlorobenzothiazole _

-4 2-mercapto-5~nitrobenzothiazole _ _ _ ?_ i 2~mercapto-6-nitrobenzothiazole

Y ?*? 2-mercapto-4~f enylbenzothiazole O.

O

2-mercapto-naphtothiazole ? 2-mercapto-6-hydroxybenzothiazole . _ _*?o The proportion of 2-mercaptothiazole corresponds to a value of up to 40$ by weight? based on the CD co

reaction mixture.

The ammonia to be used in accordance with the present invention may be added either alone or in conjunction with a heavy metal or heavy metal compound as a catalyst. _

Examples of suitable co-catalysts are the metals iron? cobalt? nickel? copper, chromium, zinc? manganese, silver? vanadium? molybdenum and cerium, their oxides as well as their inorganic or organic salts or complexes.

The heavy metal or heavy metal compound is used in quantities less than 0.1% by weight - based on 2-mercaptothiazole.

Already traces of these co-catalysts - particularly in the case of delirium developing - still. -L-

T has a remarkable catalytic efficiency and I lead no good.

r e s e__d i _ _d i t i az.o.? il - di solfur i ... _D i _c ons eque nce _? ...p? s?-j

. bile_employ quantities? , s.tr ordinarily..low...of j

j.catalyst . and . with dur r e__ more? . times....in_cire o l._o___l I water _

mother

_ Come_co -_c at al izzatoTe of heavy metal..

G-are_present. in_particular_the_copper_and_. all the components? ?? Views of copper. or r<* >As copper components, all inorganic and organic copper salts are taken into consideration.

simple .Q.._cqmple ssi _monoy_alenti_o_ bivalent. _ .5? _ Examples of appro- monovalent copper salts

.p.r.i.a..ti are chloride-,?- b?romu?ro- and cuprous iodide, compo-<? ? >- - -- -- r

_sti_of addition of these cuprous halides with carbon monoxide, cuprous salts, performed as with chlorine?

!alkaline cuprates, complete ammonia of cuprous cyanide, for example cyanidecuprates, such as potassium triphosphate cuprate (I), double salts with copper sulphocyanide!

_ jmeoso, acetatojcopperqso, cuprous sulfide and sulfides dop-_

i

f

? _ j more complex cuprous acetate, j3olfurq_rameo so e_j _

sulfides, double complexes of cuprous sulfide and alkali polysulfides. _ _ _ _ j_

! i

?_ _ Examples of r-ameic salts_apP<r>?P<ria>^<1 >are clo~

urea, bromide, sulfide, sulfate, nitrate, nitrite,

<">?

thiocyanide? cupric cyanide? cupric salts of carboxylic acids such as cupric acetate? as well as complex ammoniacids of cupric salts. Also metallic copper.

I dare I'm m<?>

o<? >. - r

and high copper oxide suitable as co-catalysts._ _ _ _ _ _ _ _ _

Preferably, cuprous chloride? cupric acetate? cupric sulfate? cupric oleate? cupric acetyl acetonate? cupric sulfide or oxycrylate?. or cuprous.

Since the heavy metal compound is used in small quantities, it is suitable for

to easily soluble heavy metal compounds

even those heavy metal compounds which have only a very broad solubility or are soluble in water only in trace amounts.

Oxygen or a gas containing oxygen is used as the oxidizing agent, preferably air. The conversion and reaction rate increase with increasing oxygen pressure or partial pressure. In general, the oxygen pressure or partial pressure is between 0.1 and

150 bar. For economic reasons, oxygen pressures or partial pressures of

0.2-10 bar.

The reaction temperature corresponds to 0.50°C, preferably 20-90°C and in particular 30-70°C. At lower temperatures the reaction rate decreases, while at higher temperatures the

selectivity of the reaction.

The reaction duration normally corresponds to: <' . >. <.. " >-<">f

but at 0? 25-6? 5 hours; under the mentioned and preferred conditions of pressure and temperature and in the presence of a

copper co-catalyst, it is less than 1 hour!

for an $80 conversion.

_ The execution of the procedure according to the

This invention is made in a simple manner for the

|

the fact that oxygen or oxygen-containing gas

'is compressed onto the reaction solution, under the indicated conditions of pressure_ and temperature, or _

IIvie.n...e fa..to pass into or through the solution?'!'' [consisting of water? 2-mercaptothiazole, catalyzed-I

heavy metal and ammonia. The rea-_ product

i

!

The precipitate is filtered or centrifuged. The water

. <. . . >;

mother can be added with fresh 2-mercaptothiazole and sent into circulation. Depending on the

What is the starting concentration level of the heavy metal catalyst? Should fresh catalyst be added after a certain number of cycles?

I

reaction. The procedure is also suitable for a coni

l

the continuous duction of the reaction.

In the process _according to the present invention_ good yields (up to 99%) and high selectivities (up to over 99%) are achieved <!>? The dithiazolyl- |_

( 2 , 20- disulfides obtainable are distinguished by a high purity. They can therefore be directly used, for example, as vulcanization aids without further purification. Thanks to the ? ?<f? ? ?

the possibility of circulating the mother water? _ ? ??-aS npn_jri on the practical problems_ of the waste water by following the procedure of the present invention. A further advantage of the process according to the present invention compared to the above-mentioned procedures lies in the _

tQ availability of up. _s o 1 y economic, safe and favourable to the environment, the absence of a separate working phase for the removal _ (elimination) from the reaction water from the solvent. _ ; _ ^ _

<? >_ Example 1 _ _

_ In a glass autoclave which is equipped with

a shirt with a cavity for circulation

r <_ ~ ? ' >r

a heating fluid; a thermometer, a measure?

A pressure vessel and a stirring device are used; 50 g (0.3 moles) of 2-hydroxybenzothiazole (MBT), 12 mg (0.6 10<~ 3 moles) of Cu(OAc) 2^2<0 f >, 20.4 g (1.2 moles) of ammonia and 320 g of water are added; the reaction mixture is heated to 50°C, forming a clear solution, and stirred vigorously.

invested with an oxygen pressure of 4 bar. Yes

it immediately plays an oxygen absorption j

!

i

and a precipitate is formed following the formation

of dibenzothiazyl disulfide (MBTS). After 1 hour, the experiment is suspended. Is the precipitate filtered?

washed with aqueous ammonia as well as with water and dried under vacuum at 70?C. In this way, 47 ? 7 g of a product are obtained which in the pure analytical data ^ c or tL [ (elemental analysis ? IR, -NN[R and MS) _ is identical to j_ and <1>H

jdibenzothiazyl-disulfide, and whose purity is deterj

mined by 100? by chromatographic analysis (P .F.|

178?C) . <?>

the mother liquor contains., based on the analysis

gas chromatography, 1.8 g of MBT not converted to . Of

consequently the conversion of MBT corresponds to 96?, 4 fo,

theoretical (selectivity?

99 ,6*0

Example 2

In the reaction apparatus described in example 1, a solution of 5Cj g is dissolved in water.

(0.3 mol) of MBT, 10.2 g (0.6 mol) of ammonia and

( 3 mg (0.015. 10 ^ moles) of Gu(OAc) o.Ho0 in 160 g of !

j<' . .... . 2 " ~ >p

[water, and reacts with oxygen in the manner of

written in example 1. The oxygen pressure cor-

responds to ? bar, the reaction temperature at 50?cj

. . After 4? 5. hours dibenzothiazil-di- is obtained

sulfide with a yield of 49.1 g, corresponding to $988

of the theoretical. The conversion is determined to be $994

-(selectivity? 99.4$).

_ Example 3 _ _ __ __ __ _

?~ _ _ ^_ .It_operates .as .in .example .1, .but .without ?g

3S . Or junta__di_Cu(OAc) 0... In this case, the _conversion--_ Ori.

O

Cx ne of mercaptobenzothiazole corresponds after 20 hours?

i ??? j $90.8, MBTS yield at .44?.9__g? equal to_.90.3$.9lel theor_

rich (selectivity 99.5)?_ _ _ ?

Examples A-8. _ __

OQ

_ In these examples the quantity of ammonia CTJ

is varied. To this end, they are made to react in turn

!

once 50 g (0.3 moles) of 2-mercaptobenzothiazole, in the

manner described in example..1; the conditions of_

..reaction as well as conversions, yields-.selectivity? ot-?

held..are summarized in,_table 2._

Examples 9-13 . .... _ _ ,_

_ In these examples, different heavy metal catalysts are used, as well as different con-

concentrations of heavy metal. For this purpose,

react 50 g (0.3 moles) of 2-mercapto-

benzothiazole under the reaction conditions employed [in Table 2 (reaction temperature 50 ?C? oxygen pressure 4 bar) as described in example -j

Pius 1; the conversions? Yields and selectivity achieved

they are also and s if indicated in the_ table _ 3^

_ Example 14 _____ _ ? _

In the reaction apparatus described in Example 1, a solution of 50 g (0* 3j?J0-1 i) of 2-mercapto-benzothiazole and 12 mg of Cu(OAc) ^?.Ho- -\ C.0' is oxidized.

o~ (0. 06. 10 ^ moles) in 360 g of aqueous ammonia (teno- Cv?

of ammonia 50 g (2?9 moles) at room temperature O r- :

O

with oxygen _ (oxygen pressure 4 bar). After re?- CT'

tion for 6.5 hours the conversion of 2-mercaptobenzothiazole corresponds to ^95.6$ and the yield of dibenzothiazyl disulfide corresponds to 47? 3 grams, equal to 95?

of the theoretical (selectivity 99 ? 5/S) ? CD -gf Example 15

In the following example, air is used as the oxygen-containing gas. In the reaction apparatus?

tion described in example 1 dissolves in 160 g j

of water a solution of 50 g (0.03 mole) of MBT, |

10.2 g (0.6 moles) of ammonia and 6 mg (0.03-10 moles)

of CuiOAc^. H^O in 160 g of water? and oxidizes at 50?C

; with air. (8 bar). After 8 hours the MBT conversion

i <. . . "" : . >: <">

j corresponds to 94, 3# and the MBTS yield corresponds to_

<. . . >?

46.6 g, equal to 93.7 # of the theoretical (selectivity 99.4$)*_

TABLE 2I (Examples 4-8)

i

! t

NH

1 Cu(OAt?) Water Temp, Pressurej Duration >onve r- Selectivity Yield? Moli (# del<' >mi , _ "?! ^ 1

(10 moles) (g) j?C of 0 (bar) of MBTS reaction ($ (*> <: >! shield of tion! of MBT of the theo

reaction) (b) m ! rico)

? :

2.3 (19.1) 0.02 90 70 2.5 1.5 86.1| ! 83.4 ;96.9

i iI I !

2.4 (10 0.04 300 5 ?0 4.0 2.5 i98, 6

1.5)

i i ! 95.4 94.1

i !

0.4 ( |3.1) 0.015 163 50 4.0 6.0 ?4.9 94^2 ; F99, 3

i | i !

!

0.1 ( 0.9) 0.06 168 ?io 4.0

r 6.5 p4?1 92,;6 98, 4

i

,06 170 70 4,0 8., L

*\\ri

TABLE 3 (Examples 9-13) j.

EH Co-catalyzes Water Duration I Conversion Yield MBTS<? >Selectivity? tor |MBT (fo) of j (mol) (e) ! reaction

(h) ; theoretical)!

( 10 <3>moles)

0.6 CuSO . 160

4 (0.015); 4.5 98.2; 97.5 99.3 i \

!

0.6 Cu(OAc) ^ <' >!

D j (0.005)1 160 8, 9.0 ;

1 !5 93? 1 ! 92,1 9

!

1 1.0 Kn(OAc) ^ I (0.06) | 300 ??5 ^1,l| 90.5 99.3 ;

\ |

! I

2 0.8 FeSO, <1 >(0.06) 160 9.0 90.4; 188.9 98.3 :

!<4 >! i

! j i ?

3 1*2 catalyzes (0)| 320 2o;o 90, ?! 90,3 99,5 absent tore

m?. B? 2AS<(>p & ? i AF|DO ROMA S.p.?

1. Procedure for the production of ditia-_

_ zo ilil { 2 ? 2<1 >)-disulfides of the general formula

R - C - N N - C - R

\ - S - S -

/ \

R'~ C - S. - C II - R'

where R and R<1 >can and s be equal or different and

each represent a hydrogen atom -

mo of halogen? a nitro group? __a_ hydroxyl group- ! o.

oO co or an alkyl or alkoxy radical having .?5_

3 j ?-6_ carbon atoms and possibly one or more substituted a: te or a cycloalkyl or alkyl radical having 6-12 carbon atoms? the substituents may each be a halogen atom?

, ^ a nitro group? a hydroxyl group? or a 7-alkyl or alkoxy radical having 1-5 carbon atoms? or in which R and H <1 >jointly form the radical:

I I

l i f t

where R" and R" <1 >, R"" and R" can be the same or different and each have the same meaning as

me R and ? ' , by catalytic oxidation of a 2-

mercaptothiazole of the general formula:

R - C - N

C - SH

/

R'- C - S

where R and R <1 >have the meaning indicated above ?

by means of oxygen or a gas containing oxygen in a

. Jt solvent in the presence of a catalyst and possibly of a heavy metal co-catalyst?

or at temperatures in the range <?>of 0-150?C? characteri-

i

due to the fact that water is used as a solvent and

?Or ammonia catalyst.

2- Process according to claim 1 and 1 is characterized by the use of ammonia

in quantities of 1-25? by weight ? depending on the mixture

of reaction.

Rome, 1 6 FEB<,>

p.p. : AKZO NV

p.: ING. BARZANO? & ZANARDO ROMA S.p.A.

TC/gt.- 8905

-

\f

^03

I FEDERAL REPUBLIC OF GERMANY

Coat of arms

Certificate 10171 K ?

1<? >Akzo GmbH in 5600 Wuppertal has filed a patent application entitled:

"Process for the production of dithiazole disulfides" on February 17, 1982 at the German Patent Office 0 .

I am a faithful copy I <( >The attached documents

and accurate from the original documents of this patent application.

The attached summary - which is attached to the application - but which does not form part of it - is in conformity with the original filed on 17 February 1982.

The application was promptly registered at the German Patent Office with the symbols C 07 D 417/12, C 08 L 21/00, C 08 K 5/46 and C 08 J 3/24 of the International Patent Classification. |

Monaco, January 25, 1983

The President of the German Patent Office

? On behalf of

F. to . Sieck

(SEAL)

No. of acts:

P 32 05 555.2

"Process for the production of dithiazole disulfides"

SUMMARY

A process for the production of dithiazolyl-(2?2<1 >)-disulfides is described.

S ? S

in particular of dibenzothiazolyl-(2? 2')-disulfides,<'>

1 j in which ui_2-m e re apio t iazo li are _co nverted into the com-|

The compounds of the title are treated with oxygen in water as a reaction medium and in the presence of ammonia as a catalyst and possibly heavy metals. The compounds of the title are used as vulcanizing agents for rubber.

i -The present invention relates to a process for the production of dithiazolyl-(2,2')-* disulfides by oxidation of 2-mercaptothiazoles by means of oxygen, in particular of dibenzothiazo-11- disulfide starting from 2-mercaptobenzothiazole.

For the production on a technical scale of di? benzothiazolyl-disulfides by oxidation of 2-o

Mercaptobenzothiazoles have been used to date in various oxidation methods. However, most of the known processes have already been the inconvenience of starting with expensive oxidizing agents compared to oxygen, for example chlorate/nitrite (Fiat Final Report 1018, page 22), nitrite/oxygen (U.S. Pat. 1,908, 935), nitrite (U.S. Pat. 2, 119, 131 and 3,062,825), chlorine (Kirk-Othmer, En-^ cyclopedia to Polymer Science and Technology (1970), Vol. 12, page 262 as well as hydroperoxides (DOS 23 09__5_84), and ozone (SU-PS 420 247)? Most of the processes indicated in the above-mentioned publications also present further drawbacks, such as the requirement of large quantities of acids, bases or other auxiliary substances, the formation sometimes of large quantities of by-products or secondary products or complicated or critical reaction conditions, with the need for careful control (this is for example the case of the use of chlorine as an oxidizing agent).

Also worth mentioning is a process for the electrolytic oxidation of 2-mercaptobenzothiazole to dibenzothiazolyl disulfide (DOS 27 43 629). I am now also interested in the oxidation of 2-mercaptobenzothiazole to dibenzothiazolyl disulfide with oxygen as the sole oxidizing agent.

According to the process of U.S. Patent 3,654,297, this is possible by using a cobalt phthalocyanine sulfate, disulfonate, trisulfonate, or transsulfonate, or mixtures thereof, as the catalyst, and carrying out the oxidation in an organic solvent, which contains less than 15 % water by weight, at temperatures of 50-80°C. (Compare also U.S. Patent 575,348; Chem. Abstr. 88 (1978), 89657 g.) The production and industrial use of this catalyst are, however, problematical. Furthermore, it is known from DOS 23 55 897 that one can The oxidation of 2-mercaptobenzothiazoles to dibenzothiazyl disulfides can be carried out using simultaneously oxygen or a gas containing oxygen and iron chloride - in particular ferric chloride - in a saturated aliphatic alcohol having 1-10 carbon atoms. This can be done at temperatures between 0 and 150°C. However, this catalyst leads to a satisfactory reaction rate only if it is used in large quantities, i.e. in the ratio of 0.8-1.5 moles per mole of 2-mercaptobenzothiazole. The decisive drawback of the process, however, is that the iron precipitates during the reaction in the form of basic salts, and the dibenzothiazolyl disulfide obtained is heavily contaminated with iron. A product obtained in this manner, for example, cannot be used as a vulcanizing agent without costly purification.

An economically interesting process for the catalytic oxidation of 2-mercaptothiazoles by oxygen is finally described in DOS 2944 225. According to this patent, a mercaptothiazole is reacted by oxygen or an oxygen-containing gas in the presence of organic solvents and tertiary amines as catalyst, possibly also heavy metals or heavy metal compounds as co-catalyst, preferably at temperatures between 20 and 90°C. The dithiazolyl-(2*2 <1>)-disulfides thus obtained are distinguished by their high purity and can be used without further purification, for example directly as rubber vulcanizing agents. In comparison with the two above-mentioned processes, in which a 2-mercaptobenzothiazole is also reacted by oxygen or an oxygen-containing gas in the presence of organic solvents and tertiary amines as catalyst, possibly also heavy metals or heavy metal compounds as co-catalyst, the

oxygen? This process is distinguished by the fact that simple and inexpensive catalysts are used in very large quantities and that these catalysts can be circulated with the mother liquor without their activity decreasing significantly.

A complementary patent application (Practice No. P 31 13 298.7) to the above-mentioned German patent application F 29 44 225 9 describes the production of disulphide sulfides with ammonia instead of tertiary amines as catalyst.

In all these processes for the oxidation of 2-mercaptobenzothiazole to dibenzothiazolyl-disulfide with oxygen as the single oxidizing agent according to U.S. Pat. No. 3,654,297, the <~>l <. >DOS 23 5 T <n>A 5 89<.>7

| and_ the DO .S 29 44 225 . (not that the ? question of_ - C-om .p .letive ?<? >- ? j" . No . of Practice P 31 13 298.7) ? organic solvents are considered necessary as solvents . On the contrary ? water as a solvent ? appeared completely unsuitable.

. Co : yes? for example according to US patent | <; >3,654. 297 it is not recommended to use a solvent^ with more than 15% water by weight. Furthermore DOS 29 44 225 _ - (compare page _16? lines 23-27) recommends_ i <. >I I not to let the proportion of water in the solvent rise above 10% by weight. More detailed tests^ !

j according to the DOS 2944 225 procedure have indi-

that with water as the only solvent does not happen!

i<. . >/ - - - - - J-! i any conversion ""rsion - - of the - 2 - --me ?r? c --a -ptobenzothiazole ^ n ?el - of j-I

| Benzothiazolyl-( 2? 2<1 >)-disulfide. If for example one ex- _

! follow the examples l8,_ 24 <e>_ 2?? indicated in J<)>0S_29 44 225

I

in water instead of the solvents indicated therein?

Under other conditions, no oxidation occurs;

as shown in Table 1.

TABLE 1 ?

Tests for the oxidation of 2-mercaptobenzothiazole (MBT)

! <' " " " " ~>

!a dibenzothiazolyl disulfide (MBTS)

Reaction conditions: 60 mmol MBT, 108 mmol

triethylamine, at temperature^

t

I

reaction temperature 70?C, pressure j_

!I

of oxygen_j?0 bar, during <! >_ _ _

f

of the reaction 6.5 hours. _ _ _ _

Solvent__ Catalyst Conversion_ Yield of 120 g of copper by MBT $ MBTS $

0.02 mmol

_ 'DOS 2944 225 isopropa-_ _ acetate ra- _ 82.7

jEs . 18 freight mei.co <8>?<,>JL

- .DOS 29 -44 225 toluene - acetate ra - - 90, 6 88.6

f Ex. 24 meico

.Test of conT

. jfronto - water cupric acetate <' >0

DOS 29 44 225

? . Ex. 28. . cupric isopropa-oleate 82.0 -80.2 j freight

Test with water copper oleate 0

forehead _

Finally, there should be a prejudice against the use of water as a solvent in the process according to the supplementary patent application No. P 3.1. 1 3,298.7 since it was known that ammonia as well as primary and secondary amines, unlike tertiary amines, are oxidized in aqueous solution by oxygen in the presence of metal catalysts. For example, it could be deduced from the section entitled "Chemisches Verhalten des Ammoniura-

" . il / ' Ions und des Ammoniaks m wassriger Losung" ("Chemical behavior of the ammonium ion and ammonia ? j in aqueous solution") in "Gmelins Handbuch der anor-| ganischen Chemie", 8th edition, Vol. 23? pages|_ 12 and following (the behavior towards oxygen in the presence of metals or metal ions is mentioned in detail on page 13? line 21^ to ? page 15 , line 4? taking particular account of copper) that ammonia is catalytically oxidized to nitrite in aqueous solution._ _ _ _

_ Especially for reasons of economy! 1 and ?i. safety? there has now been a need: to have a process for the production of: dithiazolyl-(2,2')-disulfides by oxidation of 2-mercaptobenzothiazoles by means of oxygen, which can be carried out not in organic solvents, but in the cheaper, more harmless and environmentally friendly solvent water.

The object of the present invention is therefore to provide an economical process for the production of dithiazolyl-(2, 2 ' )-d?sulphides me-? =

j <~ >j<~ >diante oxidation of 2-mercaptothiazoles by os-1

t

;sigeno in the presence of water as a solvent.

I ! It has now been surprisingly found that ' ? <" >1 f under suitable reaction conditions the oxidation of 2-mercaptothiazoles to dithiazolyl-(2, 2')-disulfides by oxygen can be carried out SUCCESSFULLY even in water as solvent, if ammonia and possibly a heavy metal derivative are used as catalyst (compare German patent application No. P 31 13 298.7). In the case of the oxidation of 2-mercaptobenzothiazole, dibenzothiazolyl-(2, 2')-disulfide of high purity was isolated in this way with good yields (up to 99% of the total) and high selectivity (up to over 99% of the total). The secondary actions which were to be expected on the basis of the indications from the literature (oxidation of ammonia or formation of sulfenamide (compare DOS 23 49 934, page 5? ! ! Lines 22-24)) have not been observed at this time.

Hypositus.

| The problem was solved by means of a pro-I <' >Ii |

t I ! '

yield for the production of dithiazolyl-(2? 2')-di~' sulfides of the general formula;

R - C - N N - C - R

<x>c - s - s - c . (i)

/ \

R?- C - S S - C - R?

where R and R? can be the same or different and ; represent respectively a hydrogen atom, a halogen atom, a nitro group, an oxygen group or an organic radical possibly substituted once or more than once such as an alkyl radical or :

? <. >? <. . >-j ! alkoxylic having 1-6 carbon atoms or a cycloalkylic or aryl radical having 6-12 carbon atoms, the substituents may be a halogen atom, a nitro group, an os- group,

! sydric or an alkyl or alkoxy radical having 1-5 carbon atoms? or in which R and R<1 >jointly form the radical;

R?

R<111 >-(II)

R?<1 ? ?>

R<1>

where R<H>, R<,M >, R.<M>", R""* can be equal or different^ and have the same meaning respectively

I have as R and R' ( by catalytic oxidation of a 2-mercaptothiazole of the general formula: ' _

R - C - N

% ,C - SH (III)

/

R'- C ~ S

:where R and R<1 >have the meaning indicated above? 'by oxygen or an oxygen-containing gas in a solvent in the presence of a catalyst and possibly a heavy metal co-catalyst at temperatures in the range 0-150<0>G, characterized by water and ammonia as catalyst.

In general, the amount of water corresponds to 1.5-12 times the weight of 2-mercaptothiazole used. Larger amounts of water should be avoided for economic reasons.

In many cases it can be advantageous to use water as the reaction medium with the addition of water-soluble organic solvents (for example alcohols).

The quantity of ammonia can be varied over a wide range; preferably, however, ammonia is used in quantities of approximately 0.5-25 µg/l.

l

jm weight? based on the reaction mixture.

i

I

_ Are the substituents from R to R""<1 >of the general formulas I, II and III preferably a chlorine or bromine atom? a hydroxyl group? a nitro group?

II

a straight-chain or branched-chain alkyl radical having 1-4 carbon atoms such as a radical-|

methyl? ethyl? propyl? isopropyl? butyl or tert-butyl? _an alkoxy radical having - -1-4 carbon atoms like a methoxy radical? |

! -i ethoxylic? propoxylic or butoxylic or a phenyl radical? tolylic? ethyl phenyl? nitro phenyl? chloro phenyl? bromo phenyl or naphthyl.

Dithiazolyl-(2? 2')-disulfides are used as rubber vulcanizing agents. The process according to the present invention is particularly significant for the production of dibenzothiazolyl-(2? 2'_)-disulfide, the most important representative of this class of compounds.

;E<1 >however suitable with equal success in production

of further compounds of this type. For the preferred production of dibenzothiazolyl-(2? 2')-disulfide the;

2-Mercaptobenzothiazole is used as a starting material. Examples of other mercaptothiazoles that_si j

I

they serve as starting materials for production

t

of further dithiazolyl-(2? 2<1 >)-disulfides of the formula-I

The general I? are among others the following compounds:j

2-mer captothiazole _

2-mercapto-4-methylthiazole _

2-mercapto-4-ethylthiazole _

2-m er cap to-4-n- prop i It i azo lo _

2-m er cap to-4 ? 5- dime t i 1 1i azole _ 2-m er o apt o- 4> 5-di-n-butyl thiazole

2-mercap to-4- f e_ni1 1i azole o_

| 2-mercapto~5-chloro-4-enylthiazole

I <. . ? ' . ~>

I 2-mercapto-4-p-bromof enyl-thiazole

_ j ? _ - _ _ _ - 2- m ? re ap t o- 4- m-n i tr .oie n il ti azo 1 o_ _

_ j_ 2-mer or hapto-4-m-chloro phenyl thiazole _

1

2-mer capto- 4-methyl<~>benzo thiazole _

2-mer capto- 5-me tilbenzo thiazole 2-mercap to-4? 5-dime tilbenzo thiazole

2-mer capto-4-phenylbenzothiazole 2-inerpto-4-methoxybenzothiazole

2-mer capto-6-methoxybenzo thiazole

2-mercapto-5? 6-dimethoxybenzothiazole

. i 2-mer c ap to-6-me toxi- 4-nitro benzo thiazole, 2-mercapto-6-ethoxybenzo thiazole

2-mer capto- 4- there? robenzo thiazole 2-mer capto-5-chlorobenzo thiazole 2-mercap to-6-dbrobenzo thiazole 2-mercapto-7-chlorobenzo thiazole 2-mer capto-5-chloro-6-methoxybenzo thiazole _ 2-mercapto-5-chloro-4-nitrobenzo thiazole

2-mercapto-5-chloro-6-nitrobenzo thiazole

, _ _2-mercapto-4? 5-dichlorobenzothiazole

2-mercapto-4, 7-dichlorobenzothiazole 2-mercapto-5-nitrobenzothiazole

2-mercapto-6-ni trobenzo thiazole

2-mer cap to - 4- feni lbenzo t lasso lo

2-mercapto-naphthothiazole

2-mercapto-6-hydroxybenzo thiazole.

The proportion of 2-mer captothiazole corresponds to a value of up to 40 wt.% depending on the reaction mixture.

_ _ The ammonia to be used according to the present invention may be added either alone or in conjunction with a heavy metal or heavy metal compound as a catalyst.

Examples of suitable co-catalysts are the metals iron? cobalt? nickel? copper, chromium? zinc? . .

| manganese, silver, vanadium, molybdenum and cerium, their oxides as well as their inorganic or organic salts or complexes.

The heavy metal or heavy metal compound is used in quantities less than 0.1 f0 by weight, based on 2-mercaptothiazole.

Even traces of these co-catalysts - polarly equal in the case of copper - still develop a notable catalytic efficiency and lead to good yields of thiazolyl sulfides. Consequently, it is possible to use extraordinarily low quantities of the catalyst and to circulate the mother water several times.

_ As a heavy metal co-catalyst, copper and all copper compounds are particularly suitable. _ As a copper compound, all inorganic copper salts are considered, including simple monovalent and bivalent compounds. _ ;_ i1 1 _ _ Examples of suitable monovalent copper salts are cuprous chloride, bromide and iodide, compounds?? <? >. <? ? "" >7i addition methods of these cuprous halides with carbon dioxide, complex copper salts such as the alkaline chlorocuprates, complete ammonia, copper cyanide salts, for example cyano cuprates, such as tricyanocuprate; potassium triacetate (I); double salts with copper sulfocyanide, cuprous acetate, cuprous sulfide, and double sulfides; complex double sulfides of cuprous acetate, cuprous sulfide, and polysulfides.

j

j alkaline fumes.

.

I <? >. i J _ _ _ _Examples of suitable copper salts are chloride, bromide? sulfide? sulfate? nitrate, nitrite?

\

f

thiocyanide? cupric cyanide? cupric salts of carboxylic acids such as cupric acetate? as well as complex ammonia-containing compounds of cupric salts. Metallic copper . <. >? <' >? and cuprous oxide are also very suitable as co-catalysts._ _

Preferably, cuprous chloride? cupric acetate? cupric sulfate? cupric oleate? cupric acetyl acetonate? cupric sulfide or cuprous oxy-' <^ ~ . >" i do are used. _____ _ _ _ _ j Since the heavy metal compound is used in small quantities, in addition to easily soluble heavy metal compounds, are <?">l <' >suitable?

<'. . " ' >! even those heavy metal compounds which have only a very broad solubility or are soluble in water only in traces.

Oxygen, oxygen, or an oxygen-containing gas, preferably air, is used as oxidizing agents. The conversion and reaction rate increase with increasing oxygen pressure or partial pressure. In general, the oxygen pressure or partial pressure is between 0.1 and 150 bar. For economic reasons, oxygen pressures or partial pressures of 0.2-10 bar are preferably used.

The reaction temperature corresponds to 0~150?C, preferably 20-90?C and in particular 30-70?C. At lower temperatures the reaction rate.<. ' >.

decreases, while at higher temperatures the selectivity of the reaction decreases.

The reaction time is typically 0.25-6.5 hours; under the aforementioned and preferred conditions of pressure and temperature and the presence of a copper co-catalyst, it is less than 1 hour for an 80% conversion.

The process of the present invention is carried out simply by pressing oxygen or oxygen-containing gas onto the reaction solution under the indicated pressure and temperature conditions or by passing it into or through the solution consisting of water, 2-mercaptothiazole, heavy metal catalyst, and ammonia. The precipitated reaction product is filtered or centrifuged. Fresh 2-mercaptothiazole can be added to the mother liquor and circulated. Depending on the starting concentration of the heavy metal catalyst, fresh catalyst must be added after a certain number of reaction cycles. The process is also suitable for continuous reaction.

In the process according to the present invention, good yields (up to 99%) and high selectivity (up to over 99%) are achieved. The dithiazolyl-(2)-2'V sulfides obtainable are characterized by a high purity. They can therefore be directly used, for example, as vulcanization auxiliaries without further purification. Thanks to the possibility of conducting the mother water into circulation, there are practically no waste water problems when carrying out the process according to the present invention. A further advantage of the process.

The difference between the present invention and the above-mentioned processes lies not only in the availability of an economical, safe and environmentally friendly alternative, but also in the absence of a separate working phase for the removal (elimination) of the reaction water from the solvent.

Example 1 _ _

In a glass autoclave which is equipped with a jacket with a cavity for the circulation of a heating liquid, a thermometer, a pressure gauge and a stirring device, 50 g (0.3 moles) of 2-mercaptobenzothiazole (MBT), 12 mg (0.6 mol) (3 moles) of Cu(OAc) 2H2O, and 100 g (0.6 mol) of Cu(OAc) 2H2O are introduced.

! 20? 4 g (1.2 moles) of ammonia and 320 g of water. The reaction mixture is heated to 50?C? forming a clear solution? Stirred vigorously and exposed to an oxygen pressure of 4 bar. Immediately, oxygen absorption is recorded and a precipitate forms following the formation of dibenzothiazyl disulfide (MBTS). After 1 hour the experiment is suspended? The precipitate is filtered? Washed with aqueous ammonia and water and ex-

. .

vacuum-treated at 70°C. In this way, 47 7 g of a product are obtained which in pure analytical data (elemental analysis, IR, ?-NMR and MS) is identical to j_ dibenzothiazyl-disulfide, and whose purity is determined to be ?00% by chromatographic analysis (M.P., 178°C).

The mother liquor contains - according to gas chromatographic analysis - 1.8 g of unconverted MBT. Consequently, the conversion of MBT corresponds to 96.0% of the theoretical yield (selectivity 9b.6).

Example ?

In the reaction apparatus described in example 1, a solution of 50 g (0.3 moles) of MBT, 10.2 g (0.6 moles) of ammonia and 3 mg (0.015. 10<? >^ moles) of Cu(0Ac) is dissolved in water in 160 g of

| water? and react with oxygen as described in example 1. The oxygen pressure is 4 bar, the reaction temperature is 50°C. After 4.5 hours, dibenzothiazyl-disulfide is obtained with a yield of 49.1 g, corresponding to 98.8% of the theoretical yield. The conversion is determined to be 99.4% (selectivity 99.4%).

. . Example 3

_ :i _ Yes. do you operate as in example 1? but. without the addition of _Cu(0Ac)2.H20...In this case the__conversion~.. of mercaptobenzothiazole corresponds after.. 20 hours. a.

$90.8, the. re sa of MBTS at 44.9 g> equal to $90.3 of the theoretical (selectivity? 99? 5)? _

Examples 4-8 _

In these examples, the amount of ammonia is varied. To this end, 50 g (0.3 moles) of 2-mercaptobenzothiazole are reacted each time as described in Example 1; the reaction conditions as well as the conversions and selectivities obtained are summarized in Table 2.

Examples 9-13 _ _ _ _ _

_ In these examples, different heavy metal catalysts are used, as well as different concentrations of the heavy metal. To this end, 50 g (0.3 mol) of 2-mercaptobenzothiazole are reacted in turn under the reaction conditions used in Table 2 (reaction temperature 50°C, oxygen pressure 4 bar) as described in Example 1; the conversions, yields, and selectivities achieved are also given in Table 3.

Example 14

In the reaction apparatus described in the 1st example, a solution of 50 g (0.3 moles) of 2-mercaptobenzothiazole and 12 mg of Cu(OAc) .H 0 (0.06.10 <J >mol) is oxidized in 36 g of aqueous ammonia (ammonia content 50 g (2.9 moles) at room temperature with oxygen (oxygen pressure 4 bar). After reaction for 6.5 hours the conversion of 2-mercaptobenzo-I

thiazole corresponds to 95.6% and the yield of dibenzothiazoli-disulfide corresponds to 47.3 grams, equal to 95.5% of the theoretical (selectivity 99.5%). _ _ _

Example 15

In the following example, air is used as the oxygen-containing gas. In the reaction apparatus described in Example 1, a solution of 50 g (0.03 mol) of MBT? ~ .j ; 10.2 g (0.6 mol) of ammonia and 6 mg (0.03 mol) of GuOAc^.H^O in 160 g of water is dissolved in 160 g of water and oxidized at 50 °C with air (8 bar). After 8 hours, the conversion of MBT corresponds to 94.3% and the yield of MBTS corresponds to 46.6 g, equal to 93.7% of the theoretical (selectivity 99.4%).

TABLE 2 (Examples <1>4-8)

NH. I !

Cu(OAc) Water Pressure! Duration With ver- j Yield |of S?le ctivity? Ilo 1 i (li del mi-: (g) di 0 (bar) reac- tion ^ MBTS {fo (56)

(lO \ioli), 2 of MBT I <' ? >SCUgllO of; of the theory) ?? m. rico

f 3 (19, 1) 0.02 90 70 2.5 1.5 86, 1 i 83.4 96.9 2.4 (1Q,5) 0.04 ; 300 50 4.0 2.5 95.4 94.1 :98.6 0.4 ? ( 3.1): 0.015 163 50 4.0 6.0 94.9 94, '2 99.3 0, 1 ( 0.9) 0.06 <: >168 70 4.0 6.5 94.1 92.6 I98.4

0.06 170 70 4.0 8.0

TABLE 3 (Examples 9-13) _

EH. Co-catalyzes Water Duration Conversion- Yield MBTS<' >Selectivity? toner (g) ; MBT reaction (i) I (95 of the theoretical j io (mol) )

(10 \l0li): <; >00 <:>

I

0.6 CuSO (0.015) 160 ; 4.5 98.2 <; >97? 5; 99.3

I

i ;

.6 CU(0AC)2 (0.005) 160 I 8.5 93.1 .92.1 j 99.0 I

1.0 ?in(0Ac)2 (0.06) 300 i 7.5 9 1. 1 : j 90? 5^99.3

0.8 PeSO (0.06) 160 <? >!- 9.0 90.4, 88.9 98.3

4 I : | <1 >I

1.2 catalyzes (or); 320 : 20.0 90.8! | 90.3 99.5 absent

_ _ _J Process for the production of dithia- _ 2 ' )-disulfides of the general formula:

R - C - N N - C - R

c - s - s - c

/

R?- C - S - C II - R'

in which the R and R<1 >can be the same or different and each represent _a hydrogen atom_? a halogen atom? a nitro group? a hydroxyl group or an alkyl or alkyl radical having 1-6 carbon atoms and possibly substituted one or more times or a cycloalkyl radical _a-<. . . >? "" <. >? " a carbon atom having 6-12 carbon atoms, the substituents of which may be a halogen atom, a nitro group, a hydroxyl group, or an alkyl or alkoxy radical having 1-5 amino groups, or . in which R<. > and R<1 > jointly form the <'>1 radical; ?

R' <1>

where R<M >and R" R"" and R"" ' can be equal or

. <V>

different and each have the same meaning as

Claims (2)

Ime R and ?', by catalytic oxidation of a 2-I mercaptothiazole of the general formula: THE R - C - N. -- ? . - - C - SH . . . R<1>- C - S where R and R' have the meaning indicated above? <1 >by oxygen or a gas containing oxygen in a jsolvent in the presence of a catalyst and possibly a heavy metal co-catalyst? at temperatures in the range of 0-150?C? characterized by the use of water as the solvent and ammonia catalyst. 2. Process according to claim 1, characterised by the use of ammonia in quantities of 1-25?S by weight? depending on the reaction mixture. For compliant translation For INO.BARZANO<1 >& ZANARDO ROMA S.p.A. TC/gt.- TO* T--? ? ; or ,y.. -/ ?Z?LQD