GB896949A - Improvements in the production of proto-anemonin and its homologues - Google Patents

Abstract

Catalytic compositions specified for use in the preparation of protoanemonin and its homologues by the dehydration/dehydrogenation of gamma-keto n-alkanoic acids and esters and amides thereof or the dehydrogenation of lactones of such acids (see Group IV(b) ) include admixtures of copper, nickel, platinum, palladium or other metal or phosphate catalysts with an alkali or alkaline earth metal oxide or a carrier, for example, in specified proportions: phosphoric acid on silica or alumina; palladium or alumina or active carbon; nickel and chromium, or copper, nickel and chromium or manganese, on silica gel; and copper and chromium on silica. Other catalysts mentioned are admixtures of calcium and nickel phosphates; 98% copper containing barium, chromium and zinc; oxides of V, Cr, Mo, W, U and other Group Va and VIa metals admixed with other oxides such as those of zinc, aluminium, magnesium, bismuth and thorium; and mixtures of two or more metal oxides especially including zinc oxide, and in addition non-volatile alkali and/or alkaline earth metal oxides, hydroxides or inorganic acid salts thereof.ALSO:Proto-anemonin or a homologue thereof is prepared according to one method by treating a lactone of a gamma-keto n-alkanoic acid with a dehydrogenation catalyst at a temperature between 250 DEG C. and 600 DEG C. in the gas phase, or with a dehydrogenation catalyst or a quinone or substituted quinone at a temperature between 70 DEG C. and 180 DEG C. in the liquid phase. In another method, the desired compound is prepared by treating a gamma-keto n-alkanoic acid or an ester or amide thereof with a dehydration catalyst and a dehydrogenation catalyst (either successively in any order or simultaneously), or with a dehydration/dehydrogenation catalyst, at a temperature between 250 DEG C. and 600 DEG C. in the gas phase, or with a dehydration catalyst and a dehydrogenation catalyst or a quinone or substituted quinone (either successively in any order or simultaneously), or with a dehydration/dehydrogenation catalyst, in the liquid phase at a temperature between 70 DEG C. and 180 DEG C. Specified starting materials are 1 : 4-pentenolides and 1 : 4-hexenolides in various isomeric forms and C5-8 gamma-keto n-alkanoic acids and their esters with lower alcohols. The reactions may be effected under elevated or reduced pressure and solvents or inert gases, e.g. water vapour, may be present. The dehydrations are preferably not carried to completion. Continuous procedures may be used. The catalysts may be used in a fixed or fluidised bed. The products may be stabilized finally with, for example, hydroquinone, pyrogallol, ascorbic acid or phenothiazine. In Examples (1)-(8), a hex-2, 3- or 4-en-1 : 4-olide is passed in vapour form at a temperature from 300 DEG C.-400 DEG C., sometimes under reduced pressure, over a catalyst comprising copper and chromium on SiO2; palladium on Al2O3 or carbon; copper, nickel and manganese on SiO2; or nickel and calcium phosphate; the product being methyl proto-anemonin. Examples (9)-(11) describe the similar treatment of pent-2- and -3-en-1 : 4-olides yielding protoanemonin and anemonin. In Examples (12) and (13), hex-2-and 3-en-1 : 4-olides are refluxed with chloranil in xylene yielding proto-anemonin. Examples (14)-(16) describe respectively the treatment of propionyl-proprionic acid, the ethyl ester thereof and levulinic acid or its ethyl ester, under reduced pressure at 400 DEG C.-470 DEG C., with some of the catalysts used in (1)-(8) to provide methyl proto-anemonin, sometimes admixed with a hexen-1 : 4-olide, or proto-anemonin, sometimes admixed with anemonin and a penten-1 : 4-olide. Numerous other dehydrogenation and dehydration/dehydrogenation catalysts are specified; the use of Raney nickel, copper and cobalt and 2 : 3-dichlor-5 : 6-dicyano-1 : 4-benzo quinone in the liquid phase dehydrogenations is also mentioned; specified dehydration catalysts include thoria, pumice and boron phosphate.