THE GENERATION AND CYCLOADDITION OF 2-AZAALLYL ANIONS AND AZOMETHINE YLIDES FROM A COMMON PRECURSOR - A NOVEL SYNTHESIS OF INDOLIZIDINES AND OTHER HETEROCYCLES

Nonstabilized azomethine ylides may be generated by the intra- or inte rmolecular N-alkylation of 2-(azaallyl)stannanes or 2-(azaallyl)silane s. The cycloaddition of these ylides with electron poor or electron ri ch dipolarophiles provides indolizidines or simple monocyclic pyrrolid ines (e.g., 5 --> 8 --> 9 --> 10). The same 2-(azaallyl)stannanes may be subjected to tin-lithium exchange to afford 2-azaallyl anions, whic h may also enter into cycloadditions (e.g., 11 --> 12 or 13). An in si tu method for the generation and cycloaddition of azomethine ylides fr om an omega-halocarbonyl compound, an alpha-stannyl amine, and a dipol arophile is also described (Table 2). (C) 1997 Elsevier Science Ltd.