Allylic Sulfones Containing Triene Moieties as Key Synthons for Carotenoid Synthesis

An efficient synthetic method for the allylic sulfone 2 containing a conjugated triene moiety has been proposed involving i) coupling of allylic sulfones 4 with the C₅ bromoallylic sulfide 5 , ii) base‐promoted dehydrosulfonation in the presence of allylic sulfide, and iii) selective oxidation of the resulting trienyl sulfide to the corresponding sulfone. Total synthesis of lycopene starting from the C₁₅ allylic sulfone 2b has been described, where the new C₁₀ bis(chloroallylic) sulfone 11 proved to be a useful substitute for the C₁₀ bis(chloroallylic) sulfide 3 , which did not require the problematic chemoselective sulfur oxidation in a conjugated polyene.