Preparation of e7/z9-alkadien-1-ols and their derivatives protected at the hydroxyl group

Claim 1

A process for the preparation of a compound of the formula I ##STR8## where R 1 is C 1 -C 8 alkyl and R 2 is hydrogen or a base-stable alcohol protective group, wherein a 7-hydroxyheptan-1-al, which may be protected at the OH function, of the formula II OHC--(CH.sub.2).sub.6 --OR.sup.2 II is subjected to a Wittig reaction with a phosphorylide of the formula III ##STR9## where R 3 and R 4 are each a low molecular weight alkyl group or are bonded to one another to form an unsubstituted or C 1 -C 4 -alkyl-substituted dioxan or dioxolan system and R 5 is alkyl, cycloalkyl, phenyl or substituted phenyl, to give a compound of the formula IV ##STR10## which is converted by the action of an acid into a trans-2-nonenal of the formula V ##STR11## which is converted by a further Wittig reaction with a phosphorylide of the formula VI ##STR12## where R 1 and R 5 have the abovementioned meanings, to a compound of the formula I, wherein said base-stable alcohol protective group R 2 is C 4 -C 12 -tert-alkyl carrying a tertiary carbon atom in the 1-position, C 3 -C 8 -trialkylsily, benzyl, C 2 -C 4 -alkanoyl, benzoyl, C 2 -C 9 -alkoxymethoxy, C 3 -C 10 -1-alkoxyethoxy, 2-furanyl, 2-tetrahydrofuranyl, 2-pyranyl, 2-tetrahydropyranyl, 1,3-dioxan-2-yl or 1,4-dioxan-2-yl.