α,α‐Disubstituted Allyl Sulfones: An approach to the synthesis of vinyl‐branched pheromone analogues

Abstract

AbstractThe two‐step alkylation of phenyl prop‐2‐enyl sulfone (1) with protected ω‐bromoalkanols and 1‐iodoalkanes (→3; see Scheme 1) followed by a Pd‐catalyzed desulfonylation with LiBH4 affords a 96:4 mixture of vinylbranched, protected alcohols and corresponding ethylidene‐branched isomers (see Scheme 2; 4 and 5, respectively). By utilizing the large difference in reactivity of mono‐ and trisubstituted CC bonds towards singlet oxygen, the ethylidene derivatives are easily removed from the mixture by photo‐oxygenation. The vinyl‐branched compounds are inert to this reaction and can be conveniently isolated in highly pure form (99.5%) and ca. 45% overall yield.