Sulfone-Metal Exchange and Alkylation of Sulfonylnitriles.

The first general sulfone-metal exchange is described. Treating substituted 2-pyridylsulfonylacetonitriles with either BuLi or Bu3 MgLi generates metalated nitriles that efficiently intercept a variety of electrophiles to afford quaternary nitriles. The 2-pyridylsulfone is critical for the sulfone-metal exchange because chelation anchors the organometallic proximal to the electrophilic, tetrasubstituted sulfone to override complex-induced deprotonation. Alkylating commercial 2-pyridinesulfonylacetonitrile with mild bases, either K2 CO3 or DBU, and subsequent sulfone-metal exchange and alkylation rapidly assembles quaternary nitriles by three alkylations, only one of which requires an organometallic reagent.