The generation and cycloaddition of 2-azaallyl anions and azomethine ylides from a common precursor. A novel synthesis of indolizidines and other heterocycles

Abstract

Nonstabilized azomethine ylides may be generated by the intra- or intermolecular N-alkylation of 2-(azaallyl)stannanes or 2-(azaallyl)silanes. The cycloaddition of these ylides with electron poor or electron rich dipolarophiles provides indolizidines or simple monocyclic pyrrolidines (e.g., 5 → 8 → 9 → 10). The same 2-(azaallyl)stannanes may be subjected to tin-lithium exchange to afford 2-azaallyl anions, which may also enter into cycloadditions (e.g., 11 → 12 or 13). An in situ method for the generation and cycloaddition of azomethine ylides from an ω-halocarbonyl compound, an α-stannyl amine, and a dipolarophile is also described (Table 2).