Stable 2-Azaallyl Salts as a Bridge between 2-Azirines and Densely Functionalized 2-Pyrroles.

An efficient protocol for the synthesis of stable 2-azaallyl anion salts by the reaction of alkyl 2-bromo-2-azirine-2-carboxylates with trimethylsilyl cyanide/BuNF has been developed. The domino reaction proceeds in four steps via the cleavage of the azirine C-C bond to provide the tetrabutylammonium salts of stereochemically pure 2-azaallyl anions having U-configuration relative to the cyano groups. The anions with an -substituted aryl group or styryl group exist as a mixture of two geometrical isomers across the N2-C3 bond.