Summary. An efficient synthesis of all-(E) vitamin A acetate from 2,2,6-trimethyl-cyclohexanone has been achieved via the intermediacy of 1-(9-acetoxy-3,7-dimethyl-nona-3,5,7-trienl-ynyl)-Z, 2,6-trimethyl-cycIohexanol (25), readily prepared in high yield by allylic rearrangement of tertiary propenols with glacial acetic acid. The key step in the synthesis is the transformation of 25 to the unsaturated ketone 27 (9-acetoxy-3,7-dimethyl-l-(2,6,6-trimethyl-cycIohex-1-enyl)-nona-3,5,7-trien-Z-one) using a novel vanadium(V)-catalysed rearrangement reaction. The carbonyl in 27 affords the means for the essential isomerization of the adjacent double bond to the (E) isomer and the product is readily transformed into the polyene by reduction and elimination. An overall yield of 18-31 % of vitamin A acetate from 2,2,6-trimethyl-cyclohexanone has been realized.The synthesis of vitamin A (1) and its derivatives has been the subject of numerous investigations [l] since the structure elucidation of the vitamin by Karrer [2] in 1931. All of the synthetic routes which have achieved commercial prominence employ p-ionone as the common starting material, and there has been considerable recent effort at improved syntheses of @-ionone and its precursors [3]. Recent developments in the catalytic alkylation of phenols [4] and their conversion to cyclohexanones [5] encouraged us to investigate new routes to vitamin A utilizing 2,2,6-trimethyl-cyclohexanone (2) as a starting material. No study of this possibility has been published since the reports by Heilbron et al. [6] and Atteitburrow et al. [7] in the 1950's.In our approach (Scheme I ) it was considered to be essential to control the configuration about the 9 , l O double bond (numbering of 1) to produce the 9-(E) isomer and to effect any reductions with very high selectivity. We utilize anovelvanadium(V)-catalysed rearrangement of an ethynyl-substituted 2,2,6-trimethyl-cyclohexanol derivative (3) to produce an 8-0x0-compound (4). The carbonyl function is a convenient device for the important isomerization of the 9,lO double bond and is easily transformed into the polyene by reduction and dehydration. The rearrangement reaction, formally analogous to the Meyer-Sckuster [8] reaction, is effected by tris(triarylsily1)vanadate catalysts, discovered by Pauling [9] and improved by Pauling et al.