Regioselective Asymmetric Alkynylation of N-Alkyl Pyridiniums.

Disclosed in this Letter is a novel asymmetric addition of alkynyl nucleophiles to N-alkylpyridinium electrophiles. The coupling is effected under mild and simple reaction conditions, affording dihydropyridine products with complete regiochemical and stereochemical control. In addition to several manipulations of the dihydropyridine products, the utility of this transformation is demonstrated through a concise, dearomative, and asymmetric synthesis of (+)-lupinine, a natural acetylcholine esterase inhibitor.