Palladium‐Catalyzed S‐Allylation of Vinyl Carbinols – Total Syntheses of Carotenoids by Julia‐Kocienski Olefination

Abstract Palladium catalyzed S ‐allylation of vinyl carbinols from ionones (or conjugated carbonyls) with 2‐mercapto‐1,3‐benzothiazole (BT‐SH) provides versatile C 15 dienyl benzothiazolyl (BT) sulfides. This Pd(dppe)Cl 2 ‐catalyzed S ‐allylation is highly selective for free allylic alcohols in the presence of allylic acetates, resulting in 3‐ or 4‐acetoxy C 15 dienyl BT‐sulfides suitable for xanthophyll synthesis. The corresponding C 15 dienyl BT‐sulfones undergo Julia‐Kocienski olefination reactions with C 10 2,7‐dimethyl‐2,4,6‐octatrienedial under mild conditions to produce carotenoids natural products. Efficient synthesis is achieved for a range of carotenoids including xanthophylls such as iso‐zeaxanthin, zeaxanthin, and lutein as well as carotenes like β‐carotene, ϵ‐carotene, and 9′‐ Z ‐phenyl‐carotene.