Arylsulfonylacetylenes as Alkynylating Reagents

The unexpected “anti-Michael” addition of RLi to β-substituted sulfonylacetylenes, followed by in situ elimination of the ion sulfinate, allows the alkynylation of C(sp²) and C(sp³). Aryl and heteroaryl acetylenes, enynes, and mono and dialkyl alkynes can be obtained in very high yields under very mild conditions, avoiding the use of transition metals as catalysts and, in many cases, haloderivatives as starting materials. Furthermore, the use of lithium 2-p-tolylsulfinyl benzylcarbanions as nucleophiles of these reactions allows their stereocontrolled alkynylation, affording enantiomerically pure alkynes or enantioenriched allenes depending on the protonating agent (NH₄Cl or H₂O).