WO1993002998A1 - Bicyclic compounds, their preparation and their use - Google Patents

Abstract

Disclosed are bicyclic compounds of general formula (I), in which R is: (a) -CH=CR?1-CH(OH)-CH2?R?2, (b) -CH=CR?1-CO-CH2?R?2, (c), (d), (e) a cyclohexyl group which may be substituted in any of various positions with an OH and a methyl group and may also have one double bond; an in which R?1 and R?2, independently of each other, may be hydrogen or an alkyl group with 1 to 3 C-atoms. These compounds have odour characteristics with a complex sandalwood character and high diffusion power and can be mixed in widely varying proportions with each other and with other odoriferous substances to give new scent compositions, generally containing 1 to 70 % by wt. relative to the total composition. These compositions can be used to scent cosmetic preparations and industrial products, as well as in alcohol-based fragrances.

Description

 "Bicvclic compounds, their preparation and use"

The invention relates to new bicyclic compounds, a process for their preparation and their use as fragrances.

Many natural odoriferous substances are available in a completely inadequate amount, measured according to need. For example, 5,000 kg of rose petals are required to obtain 1 kg of rose oil; The consequences are a very limited world production and a high price. It is therefore clear that the fragrance industry has a constant need for new fragrances with interesting fragrance notes in order to supplement the range of naturally available fragrances and to make the necessary adaptations to changing fashionable tastes, as well as the constantly increasing need for odor improvers for everyday products To cover needs such as cosmetics and cleaning agents.

In addition, there is generally a constant need for synthetic fragrances which can be produced cheaply and with a constant quality and which have desired olfactory properties, i.e. have pleasant, near-natural and qualitatively novel odor profiles of sufficient intensity and are able to advantageously influence the fragrance of cosmetic and consumer goods. Therefore, compounds were sought which should have characteristic new odor profiles with high adhesive strength, odor intensity and radiance.

From a perfume point of view, sandalwood oil is particularly valued and valuable. It is obtained from the heartwood of sandalwood, a tropical semi-parasite that occurs in India and Malaysia, by steam distillation. Heartwood appears after about ten years and only begins to develop more quickly in twenty-year-old trees. Fully grown trees are cleared at the age of 30 to 60 years because the roots are particularly rich in fragrant heartwood [cf. ETMorris, Dragoco Report 1983 (30) 40]. It is therefore understandable that fragrance research is constantly striving to develop suitable substitutes for natural sandalwood oil.

R.E. Naipawer outlined the focal points in the development of suitable substitutes for natural sandalwood oil in a review [in: B.M. Lawrence, B.D. Mookherjee, B.J. Willis (ed.) R "Flavors and Fragrances: A World Perspective"; Elsevier Publishers, Amsterdam 1988]. Accordingly, the terpenylcyclohexanols, which were offered by various manufacturers, were among the first synthetic fragrances with a sandalwood smell. The introduction of CamphoTenyl derivatives in the mid-1970s then marked a renaissance in the field of synthetic sandal fragrances [cf. also E.J. Brunke, Dragoco Report 1983 (30) 139]; In this class of odoriferous substances, campholenaldehyde, a trimethyl-substituted cyclopentene derivative, which was readily accessible from α-pinene, was used as a building block. A representative of this type is e.g. Brahmanol (R) from Dragoco, which is still commercially available today.

Finally, in the early 1980s, special bicyclic compounds that smell like sandals were reported. For example, DE 2833283 describes norbornane or norbornene compounds which carry a methyl group on the bicyclus and which have a 3-hydroxy-2-methylpent-1-enyl radical as the side chain. Such compounds are said to have a fragrance similar to that of α or β-Santalol. This observation is remarkable since EJBrunke had shortly before attributed compounds with camphanyl residue only very weak odor effects when trying to formulate a relationship between chemical structure and sandalwood scent [Dragoco Report 1981 (28) 251]. The suitability of special bicyclic compounds as fragrances with a sandal scent was a further confirmation of the general experience that the olfactory properties of known fragrances do not allow any conclusive conclusions to be drawn about the properties of structurally related compounds, because neither the mechanism of fragrance perception nor the influence of chemical structure on fragrance perception are sufficiently researched, so normally It cannot be foreseen whether a changed structure of known fragrances leads to a change in the olfactory properties and whether these changes are assessed positively or negatively.

The following are known from the prior art as further bicyclic compounds: (1) Isocamphanyl derivatives which contain a side chain with two double bonds or a saturated side chain with a hydroxyl or carbonyl function [JP 83/180443, cited from Chem. Abstr. 100, 68566c]. (2) A by G.Buchbauer et al. synthesized isocamphane derivative with a 2-methylprop-2-en-l-ol side chain, the smell of which is described as camphorous-floral-woody [monthly h. Chem. 1987 (118) 511]. (3) Bicyclo [3.1.1] derivatives with a sandal scent, which are derived from α- or β-pinene, see US Pat. No. 4,424,378 and DE 2708048.

In addition, Japanese working groups have described tricyclic compounds with a useful sandal scent, see JP 59/10536 (Chem. Abstr. 101, 54622b and EP 162672.

It has now been found that bicyclic compounds of the general formula (I) meet the requirements for a fragrance excellently in all respects and are advantageously used as fragrances with differently nuanced odor notes, including sandalwood notes, with good adhesive strength can.

The invention therefore relates to bicyclic compounds of the general formula (I)

(I)

worin der Rest R für eine Gruppe

wherein the radical R for a group

(a) -CH = CR - CH (0H) -CH ₂ R ² ,

(b) -CH = CRl-CO-CH ₂ R ² ,

(c) -CH-C-CH2R-.

I.

CHO

(d) -CH = C-CH ₂ Rl or

I CH ₂ 0H

(e) a cyclohexyl radical which bears a 0H group and a methyl group at different positions and can optionally be simply unsaturated, and in which the radicals R ¹ and R ² independently of one another are hydrogen or an alkyl group having 1 to 3 C atoms mean.

Particular preference is given to those compounds of the general formula (I) according to the invention in which the radical R represents a group -CH = CRl-CH (OH) - CH ₂ R ² and in which the radicals Rl and R ² independently of one another are hydrogen or mean a methyl group and in particular those compounds (I) in which the double bond has an E configuration.

Another object of the invention is a process for the preparation of the bicyclic compounds of the general formula (I), in which R has the meaning given above, by dehydrating base-catalyzed aldol condensation of 3,3-dimethyl-2-norbornane-acetaldehyde with the corresponding the short-chain aliphatic ketones or aldehydes to the compounds (Ib) or (Ic) and their reduction, for example using complex hydrides to the alkyl alcohols (Ia) or (Id). The cyclohexanols of the formula (Ie) are prepared by condensation of 3,3-dimethyl-2-norbornane acetaldehyde with 2 molecules of acetoacetic acid ester to give a cyclohexenone ester which, after saponification and decarboxylation, gives a cyclohexenone. This is converted to the allylic alcohols by reduction, for example using complex hydrides, or to the cyclohexanols by catalytic hydrogenation. The individual steps in the preparation of the new compounds (I) are carried out according to known synthetic methods of organic chemistry. As an out 3,3-Dimethyl-2-norbornane acetaldehyde (II) is used as a material, which is accessible by hydroformylation of isocamphene in the form of a 1: 1 mixture of the exo- and endo-isomers, for example according to Example 2 of the German patent application DE 2849 742.

The aldehyde (II) can be in the presence of conventional catalysts with corresponding short-chain aldehydes or ketones, e.g. React acet-, propion-, butyr-, isobutyraldehyde, acetone, 2-butanone or 3-pentanone in a mixed aldol condensation, the corresponding α, β-unsaturated aldol condensation products (Ib) being obtained directly via intermediate aldol condensation products with elimination of water. or (Ic) can be obtained. The reaction is expediently carried out with an excess of the reactive and more volatile component. Examples of catalysts are Sodium hydroxide, sodium methoxide, sodium amide, potassium tert-butanolate or heterogeneous catalysts such as potassium fluoride on aluminum oxide are possible. The compounds (I) obtained in this procedure are predominantly E-configured on the double bond.

The carbonyl function of the aldol condensation products (Ib) or (Ic) can be reduced to the OH group in a further reaction, e.g. by means of complex hydrides such as lithium aluminum hydride or lithium or sodium borohydride or according to Meerwein-Pondorf. The allyl alcohols (Ia) and (Id) are obtained in this way.

In addition, the new compounds (le) can be prepared by condensing (II) with 2 molecules of an acetoacetic ester, for example ethyl acetoacetate, in the presence of a base, for example pyrrolidine or piperidine, a 4-carbethoxy-3- methyl-2-cyclohexen-l-one is formed. This is saponified with the addition of a base, for example potassium hydroxide, sodium hydroxide, to give the corresponding carboxylic acid salt, which is converted into the free acid by cooking with, for example, p-toluenesulfonic acid or sulfuric acid can be transferred, which decarboxylates immediately under the reaction conditions and provides the cyclohexenone. The carbonyl function of the products obtained in this way can be selectively reduced to the alcohol function by means of complex hydrides such as NaBH4, LiAlH. *., KBH4, LiBH4. In this way, cyclohexenols are obtained which can be converted into the corresponding cyclohexanols by catalytic hydrogenation, for example in the presence of nickel, palladium or platinum catalysts.

The compounds (I) can then be prepared by conventional methods, e.g. can be purified by distillation.

The compounds according to the invention are odoriferous substances with differently nuanced, intensely woody odor notes and exceptional adhesive strength. They differ from the bicyclic compounds described in the prior art by characteristic, qualitatively significantly different odor profiles.

Another object of the invention is therefore the use of the bicyclic compounds of the general formula (I) as fragrances.

In particular, the compounds (Ia) have remarkable odor properties, such as are very sought after in the fragrance industry, namely sandalwood-like with very complex shades and great radiance.

The particular smell characteristic of the compounds (Ia) of the sandalwood type according to the invention is original and novel and differs significantly from the smell characteristic of the bicyclic and tricyclic compounds known as fragrances, which is particularly surprising. In perfume compositions, the compounds (Ia) enhance the harmony, naturalness and charisma, as well as the adhesion, the dosage being matched to the desired fragrance note, taking into account the other constituents of the composition.

These olfactory properties were not predictable and the compounds (Ia) were not expected to be advantageous in a range which is not covered by the known bicyclic compounds can be used as a fragrance or as a component of fragrance compositions.

The compounds of the general formula (Ib) are notable for woody, balsamic scent notes reminiscent of Jonone, while the fragrance profile of the compounds of type Ib and Ic can be described as fruity, woody, reminiscent of Damascone.

Because of their odor profile, the compounds of the formula (I) are particularly suitable for modifying and enhancing known compositions. Particularly to be emphasized is their extraordinary olfactory strength, which generally contributes to the refinement of the composition.

The compounds of formula (I) can be used with numerous known fragrance ingredients, e.g. combine other fragrances of natural, synthetic or partially synthetic origin, essential oils and plant extracts. The range of natural fragrances can include both volatile, medium and low volatile components and that of synthetic fragrances includes representatives from practically all classes of substances. Examples are:

(a) Natural products such as tree moss absolute, basil oil, agricultural oils such as bergamot oil, mandarin oil, etc., mastic absolute, myrtle oil, palmarosa oil, patchouli oil, petitgrain oil, Paraguay, Wer utöl,

(b) alcohols such as farnesol, geraniol, linalool, nerol, phenylethyl alcohol, rhodinol, cinnamon alcohol, Sandalore [3-methyl-5- (2.2.3-trimethylcyclopent-3-en-l-yl) pentan-2-ol] , Sandela [3-isocamphyl- (5) -cyclohexanol],

(c) aldehydes such as citral, helional ^R , oc-hexylcinnamaldehyde, hydroxycitronellal ^, lalial ^R [p-tert-butyl-oc-methyldihydrocinnamaldehyde], methylnonyl acetaldehyde, tetrahydrocitral, heliotropin,

(d) Ketones such as allyl ionone, ionone, β-ionone, isoraldein [methyl ionone], irone

(e) esters such as allylphenoxyacetate, benzyl salicylate, cinna yl propionate, citronellyl acetate, citronellyl ethoxylate, decyl acetate, dimethylbenzylcarbinylacetate, ethyl acetoacetate, hexenyl isobutyrate, linalyl acetate, methyldihydrojyl acetate, viethyl acetate, viethyl acetate,

(f) lactones such as gamma-undecalactone, l-0xaspiro [4.4] nonan-2-one, as well as various other components often used in perfumery such as ketone oschus, indole, p-menthan-8-thiol-3-one, methyleugenol.

Also noteworthy is the way in which the compounds of structure (I), in particular (la), round off and harmonize the olfactory notes of a wide range of known compositions, but without dominating in an unpleasant manner.

Some of the compounds according to the invention contain chiral centers, so that these compounds can exist in different spatial forms. In the context of conventional syntheses, the compounds according to the invention are obtained as mixtures of the corresponding isomers and are used as such as fragrances.

The usable proportions of the compounds according to the invention or their mixtures in fragrance compositions range from 1 to 70 percent by weight, based on the mixture as a whole. Mixtures of the compounds (I) according to the invention and compositions of this type can be used both for perfuming cosmetic preparations such as lotions, creams, shampoos, soaps, ointments, powders, aerosols, toothpastes, mouthwashes, deodorants and in alcoholic perfumery (for example Eau de Cologne , Eau de toilette, extras) can be used. There is also an application for perfuming technical products such as detergents and cleaning agents, fabric softeners and textile treatment agents or tobacco. To perfume these various products, the compositions are added to them in an olfactory effective amount, in particular in a concentration of 0.05 to 2 percent by weight, based on the entire product. However, these values should not represent any limit values, since the experienced perfume can achieve effects with even lower concentrations or can build up new complexes with even higher doses.

The following examples are intended to explain the subject matter of the invention and are not to be interpreted as restrictive. Examples

1. Preparation of precursor II

The compounds of the general formula Ia were prepared starting from 3,3-dimethyl-2-norbornane acetaldehyde II, which was obtained from camphene by known methods by hydroformylation in the presence of a rhodium or cobalt catalyst. The aldehyde was obtained as a 1: 1 mixture of exo and endo product. The products which are likewise possible according to the mechanism of hydroformylation and in which the aldehyde group is located directly on the bicyclus could not be detected.

2. Preparation of the compounds I according to the invention

2.1. Type (Ib) compounds

Example 1; 1- (isocamphan-10-yl) -l-penten-3-one

In a 250 ml three-necked flask, 49.8 g of the aldehyde II were mixed with 108 g of 2-butanone at 10 ° C. and under a nitrogen atmosphere. Then 40 g of a potassium fluoride-doped aluminum oxide (prepared by suspending 40 g aluminum oxide in 100 g 40% aqueous KF solution and removing the majority of water in vacuo) were added and the suspension was stirred at 50 ° C. for 10 hours. The reaction mixture was filtered, concentrated on a Rotavapor and distilled on a Vigreux column. This gave 27.2 g of a product mixture which, according to gas chromatographic analysis, contained four pairs of enantiomers in approximately the same molar proportions. The crude mixture was subjected to a fractional distillation on a spinning band column. The main amount of 15.1 g went in High vacuum (0.03 mbar) at a head temperature of 84 - 87 ° C and had a gas chromatographic purity of 97%. The IR spectrum showed bands at 2951 cm " ¹ , 1671 cm ^-1 , 1630 c ^-1 (, ß-unsaturated ketone) and at 1386 cm" ¹ , 1364 cm " ¹ (geminal methyl groups). Odor: caramel, Sugar color note

Example 2: 1- (Isocamphan-10-yl) -2-methyl-1-penten-3-one

In a 250 ml three-necked flask, 49.8 g of the aldehyde II were mixed with 129 g of 3-pentanone and 40 g of aluminum oxide-potassium fluoride were suspended under nitrogen while stirring. The mixture was stirred at 50 ° C for 5 hours. The aldehyde was then completely converted. The catalyst was filtered off, the filtrate was concentrated on a rotavapor and distilled on a Vigreux condenser. 43.8 g of a crude mixture were obtained which, as the main product, contained a mixture of the condensation products (endo and exo compound). The fine elution gave 32.3 g of the product-isomer mixture with a boiling point of 91-92 ° C / 0.02 mbar and a purity of 98% determined by gas chromatography.

The IR spectrum showed adsorption at 2952 cm " ¹ , 1672 cm" ¹ and 1640 cm ^-1 (, β-unsaturated ketone) and at 1386 cm ^-1 and 1364 cm ^-1 (geminal methyl groups). Odor: note of allyl jonon, note of sour milk

2.2. Type (la) connections

Example 3; 1- (isocamphan-10-yl) -l-penten-3-ol

7.6 g of sodium borohydride were suspended in 150 ml of ethanol in a 500 ml three-necked flask. 66 g of l- (isocamphan-10-yl) -l-penten-3-one (isomer mixture from Example 1) were dissolved in 80 ml of ethanol and metered continuously into the stirred suspension in 15 minutes. The temperature of the reaction mixture rose to about 30 ° C. The mixture was then heated under reflux for 20 minutes and then allowed to cool. For working up, it was poured onto a saturated ammonium chloride solution / ice Mix and extracted several times with ether. The combined organic phases were washed neutral with water, dried over potassium carbonate and concentrated. The subsequent distillation through a 30 cm Vigreux column gave 44.2 g of the main run with a boiling point of 99-105 ° C / 0.08 mbar.

The IR spectrum showed absorption bands at 3342 cm " ¹ and at 1384 and 1364 cm" ¹ (according to methyl groups). Smell: woody, sandalwood

Example 4: 1- (Isocamphan-10-yl) -2-methyl-1-penten-3-ol

57 g of sodium borohydride were suspended in 2 l of ethanol in a 4-1 three-necked flask. A solution of 600 g of (isocamphan-10-yl) -2-methyl-1-penten-3-one (Example 2) in 400 ml of ethanol was metered into the suspension stirred at room temperature in about 30 minutes in such a way that the temperature the mixture did not rise above 30 ° C. After stirring for one hour at 30 ° C., the mixture was boiled under reflux for one hour. After cooling, the mixture was poured onto 3 liters of an ammonium chloride solution / ice mixture and extracted several times with ether. After washing with water and drying over potassium carbonate, the ether phases were concentrated and the crude mixture was distilled through a 60 cm Vigreux column. The main run of 311 g went at 96 - 98 ^o C / 0.005 mbar. The IR spectrum of this compound differed from that of Example 2 only in the fingerprint range. The characteristic bands had the same wave numbers. Smell: strong sandalwood note, woody.

2.3. Type (Ic) compounds

Example 5: 3- (Isocamphan-10-yl) -2-methyl-2-propenaldehyde

49.8 g of 3,3-dimethyl-2-norbornanoacetaldehyde and 43.5 g of propionaldehyde were mixed in a 250 ml three-necked flask at room temperature. Under a nitrogen atmosphere and vigorous stirring, 10.8 g of a 30% strength sodium methoxide solution in methanol were added to the mixture at room temperature metered in continuously over a period of 2 hours. After the end of the addition, stirring was continued for 6 hours at an internal temperature of 50 ° C. The mixture was carefully neutralized with 10% sulfuric acid and extracted with ether. The ether phases were washed free of salt, dried over magnesium sulfate, concentrated and the residue was distilled through a 30 cm Vigrauux column. The main run with 28.2 g went over at 82 - 83 ° C / - 0.005 mbar. The IR spectrum (film on NaCl) of the isomer mixture showed bands at 2954 cm ¹ , 2875 cm ¹ and 2707 cm ¹ (H-C0), 1689 cm ¹ (C = 0), 1643 cm ¹ (C = C), 1385 cm ¹ and 1364 cm ¹ (according to methyl groups). Smell: fresh, fruity, woody, isononyl note

2.4. Type (Id) connections

Example 6: 3- (Isocamphan-10-y1) -2-methy1-2-propenol

8.7 g of sodium borohydride were suspended in 150 ml of ethanol. A solution of 32 g of 3- (isocamphan-lOyl) -2-methy1-2-propenal in 75 ml of ethanol was rapidly metered in at room temperature with stirring. The mixture warmed to 30 ° C. The reaction was heated to reflux for 30 minutes to complete the reaction. After cooling, the mixture was poured onto a saturated ammonium chloride solution / ice mixture and extracted with ether. The ether phases were washed with water, dried over potassium carbonate, concentrated and distilled on a 30 cm Vigreux column. 13.7 g main run went over at 74 - 80 ° C / 0.01 mbar. The IR spectrum (film on NaCl) showed bands at 3325 cm ¹ (-0H), 2951 cm " ¹ , 1385 and 1364 cm" ¹ (geminal methyl groups). Smell: woody, fruity, pear note

2.5. Type (le) connections

Example 7: 5- (Isocamphan-10-yl) -3-methyl-2-cyclohexen-1-ol

In a 500 ml three-necked flask, 84 g of 3,3-dimethylnorbornanacetaldehyd (manufactured according to DE 2849742, Example 2) were mixed with 156 g of ethyl acetoacetate and cooled to 5 ° C. using an ice bath. After that 4.2 ml of 21% ethanolic piperidine solution were added to the mixture and stirred overnight. The mixture was allowed to come to room temperature, 18 ml of 21% ethanolic piperidine solution was added and the mixture was stirred for 24 hours. This procedure was repeated three more times. The mixture was then heated to reflux for 7 hours. After cooling, the mixture was concentrated to 200 ml by stripping off the ethanol in a water jet vacuum. The reaction mixture, 420 ml of water, 420 ml of methanol and 24 g of sodium hydroxide were dissolved in a 1 1 three-necked flask and heated under reflux for 16 hours. After cooling, the mixture was neutralized with 10% hydrochloric acid and extracted with ether. After neutral washing, the ether phases were dried over sodium sulfate, filtered and concentrated. The purification was carried out by distillation overhead in a high vacuum. The majority of the product [5- (isocamphen-10-yl) -3-methyl-cyclo-hex-2-en-1-one] passed at 155 ° C./0.07 mbar with a purity of 98% determined by gas chromatography . The IR spectrum (film on NaCl) showed absorption at 2948, 1671 (C = 0), 1635 (C = C), 1379 and 1365 cm " ^1. Odor: woody, fruity, German chamomile.

In a 250 ml three-necked flask, 5 g of sodium boranate were suspended in 50 ml of ethanol and a solution of 24.6 g of 5- (isocamphan-10-yl) -3-methyl-cyclohex-2-en-1-one in 50 ml Ethanol was continuously added dropwise at room temperature. After the weakly exothermic reaction had subsided, the mixture was stirred for 1 hour, the mixture was poured onto ammonium chloride / ice and extracted with ether. The organic phases were dried over sodium sulfate, filtered and concentrated. Distillation via a Kugelrohr (air bath temperature 170 ° C) in a high vacuum (0.03 mbar) provided 15.2 g of a uniform product by gas chromatography. The IR spectrum (film on NaCl) showed bands at 3333 (-0H), 2928 and 1029 (C-0) cm " ^1. Odor: slightly woody, resinous.

Example 8; 5- (isocamphan-10-yl) -3-methyl-cyclohexan-l-ol

25 g of 5- (isocamphan-10-yl) -3-methyl-2-cyclohexen-1-ol (Example 7), 100 ml of ethanol and 1 g of 5% palladium on A- Charcoal submitted and pressed after flushing with nitrogen 10 bar hydrogen pressure. After a hydrogenation time of 4 hours at room temperature, the hydrogen uptake ceased. The catalyst was filtered off, the ethanol was distilled off and the residue was purified by bulb tube distillation. At an air bath temperature of 155 ° C and in a high vacuum of 0.03 mbar, 11.4 g of gas-chromatographically uniform product passed over. The IR spectrum shows absorptions at 3350 (-0H), 2949, 1384 and 1364 (geminal methyl groups) and at 1026 (C-0) cm " ^1. Odor: slightly woody, balsamic.

Composition example 1

Odor characteristic: floral (rose)

1000

-) DPG = dipropylene glycol

The combination of example 3 reinforces the floral character of the composition in the top note and gives the composition a fresh, warm naturalness.

Position example 2

Odor characteristic: fancy lavender

1000 1000

• DPG = dipropylene glycol) lPM = isopropyl myristate

Mix B is much more harmonious than Mix A. The lavender character is more pronounced and natural warmth.

Claims

Patent claims 1. Bicyclic compounds of the general formula (I),

wherein the radical R for a group (a) -CH = CR - CH (0H) -CH ₂ R ² , (b) -CH = CR - C0-CH ₂ R ² , (c) -CH = C-CH ₂ R-, I. CHO (d) -CH = C-CH ₂ R- or I CH ₂ 0H (e) a cyclohexyl radical which bears an OH group and a methyl group at different positions and which may optionally be monounsaturated and in which the radicals R ¹ and R ² independently of one another are hydrogen or an alkyl group having 1 to 3 C atoms, 2. Bicyclic compounds according to claim 1, wherein the radical R is a group -CH = CR - CH (0H) -CH ₂ R ² and wherein the radicals R ¹ and R ² independently of one another are hydrogen or a methyl group. 3. Bicyclic compounds according to claim 2, wherein the double bond has the E configuration. 4. Process for the preparation of bicyclic compounds of the general formula (I)

wherein the radical R for a group (a) -CH-CRi-OKOHj-CH-R ² , (b) -CH ^ i-CO-CH ^ ² , (c) -CH = C-CH ₂ R-, I CHO (d) -CH'-C-CH ^ ¹ or I CH ₂ 0H (e) a cyclohexyl radical which carries a 0H group and a methyl group at different positions and can optionally be simply unsaturated, and in which the radicals R ¹ , R ² and R3 independently of one another are hydrogen or an alkyl group with 1 to 3 C atoms mean, by reaction of 3,3-dimethyl-2-norbornane acetaldehyde with α) the corresponding short-chain aliphatic ketones or aldehydes in a dehydrating, base-catalyzed aldol condensation to give the compounds (Ib) or (Ic) and their reduction, for example using complex hydrides to give the allyl alcohols (la) or (Id) or β) twice the molar amount of acetoacetic acid ester to give the cyclohexenone ester, its saponification and decarboxylation to give the cyclohexenone and its reduction, for example using complex hydrides, optionally followed by a catalytic hydrogenation of the C = C double bond to the compounds (le). 5. Use of bicyclic compounds of formula (I) according to one of claims 1 to 4 as fragrances. 6. Fragrance compositions containing a bicyclic compound of the formula (I) according to Claims 1 to 4 in an amount of 1-70% by weight, based on the overall composition. 7. Use of mixtures of bicyclic compounds of formula I according to claim 1 to 4 as fragrances in cosmetic preparations, technical products or alcoholic perfumery.