α,α-Disubstituted Allyl Sulfones: An Approach to the Synthesis of Vinyl-Branched Pheromone Analogues

Article abstract of DOI:10.1002/hlca.19940770510

The 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 vinyl-branched, 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 (99.5percent) and ca. 45percent overall yield.