Process for the manufacture of odorants and intermediates used therein

#1. Field of the Invention

#The invention concerns a process for the manufacture of odorants, and novel nitriles used therein.

#2. Background Art

#The usual abbreviated representation of the structural formulae which are used in chemistry, especially carotinoid chemistry, are used herein. Aliphatic chains and cyclohexene rings and methyl substituents themselves are represented by single lines. In the definition of the compounds of formulas II and IV, "lower alkyl" signifies especially a straight-chain or branched alkyl residue containing 1 to 6 carbon atoms, such as, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, tert.butyl, n-pentyl, neopentyl and n-hexyl. "Aryl" signifies in the scope of the present invention especially a phenyl group which is optionally mono- or multiply-substituted with methyl, such as, for example, phenyl, o-, m- or p-tolyl and the xylyls.

#Geometric isomerism occurs by virtue of the presence of the aliphatic C.dbd.C double bond in the compounds of formulas I and II, i.e, the compound I or II is present in the cis- (Z-) form or the trans- (E-) form. Moreover, the possible presence of an asymmetric carbon atom means that the compounds II can occur in optically isomeric forms. Unless otherwise indicated, formulas I and, respectively, II are intended to embrace the isomeric forms which are possible as well as mixtures of isomers.

#The saponification of the compound of general formula II and, where applicable, the subsequent decarboxylation can conveniently be carried out by treating the compound of formula II in an inert protic organic solvent such as an alcohol, e.g. ethanol or isopropanol, or a glycol, e.g. mono-, di- or triethylene glycol; in an aromatic hydrocarbon, e.g. benzene, toluene or a xylene; in a cyclic ether, e.g. tetrahydrofuran or dioxan; or in water with a base at temperatures between about 20.degree. C. and about 130.degree. C., especially at the reflux temperature of the reaction mixture. Alkali metal hydroxides are preferably used as the base, with sodium hydroxide and potassium hydroxide being especially preferred. If R in formula II signifies an ester group, this is converted under the reaction conditions into the carboxy group which, in turn, is then decarboxylated. The reaction which may take several hours to complete, is worked-up in a manner known per se, e.g. by acidifying the mixture with sulphuric acid, extracting with a water-immiscible organic solvent such as, for example, diethyl ether, purifying the organic phase and evaporating the organic solvent. Particulars of this type of reaction are described, for example, in Organikum, 17th Edition, 1988, page 424.