Synthesis of Enantiopure 1,5-Enynes and 1,5-Diynes with Propargylic Quaternary Centers

Diastereoselective quaternization of ortho-sulfinylbenzyl-methylpropargylic carbanions has been carried out with various allylic, propargylic, and benzylic halides. The stereoselectivity is efficiently controlled by the sulfinyl group, acting as a remote chiral auxiliary. Desulfinylation of the resulting compounds with tBuLi provides access to enantiopure 1,5-enynes, 1,5-diynes, and 4-arylalkynes bearing all-carbon quaternary propargylic centers.