| abstract |
The invention comprises unsaturated aldehydes of general formula <FORM:1031076/C2/1> in which R is a hydrogen atom or an acyl group derived from a carboxylic acid, R may be, for example, formyl, acetyl, propionyl, butyryl, valeroyl, phenacetyl, benzoyl, nitrobenzoyl or anisoyl. The compound in which R represents hydrogen may be prepared as follows: 3,7 - dimethyl - octyn - (1) - diol - (3,7) is partially hydrogenated in the presence of a catalyst to produce 3,7-dimethyl-octen-(1)-diol-(3,7) which is then oxidized, for example by chromic acid in one stage or in two stages by first converting the diol into a 1-halo-3,7-dimethyl-7-hydroxy-octene-(2) and then oxidizing this by nitronic acid oxidation. The compounds in which R represents an acyl group may be prepared by converting a carboxylic acid diester of formula <FORM:1031076/C2/2> in which R1 and R2 each represent an acyl group to the corresponding allemic diester [3,7 - dimethyl - 1,7 - diacyloxy - octadiene-(1,2)] in the presence of a re-arrangement catalyst, e.g. silver carbonate, silver acetate, silver trifluoroacetate, silver nitrate, silver fluoroborate, silver perchlorate, copper powder or copper acetate, followed by partial saponification of the re-arrangement product. |