Protodestannylation or protodesilylation of (2-azaallyl) stannanes or (2-azaallyl) silanes led to the formation of nonstabilized N-unsubstituted azomethine ylides, which underwent cycloadditions with electron-poor alkenes to produce 2-alkyl-or 2, 5-dialkylpyrrolidines. 1, 3- Disubstituted ylides derived from the stannanes and silanes gave stereochemically complementary results; the stannanes led to trans-2, 5-dialkylpyrrolidines with high ...