Formation and cycloaddition of nonstabilized N-unsubstituted azomethine ylides from (2-azaallyl)stannanes and (2-azaallyl)silanes

Protodestannylation or protodesilylation of (2-azaallyl)stannanes or (2-aza allyl)silanes led to the formation of nonstabilized N-unsubstituted azometh ine ylides, which underwent cycloadditions with electron-poor alkenes to pr oduce 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 stereoselect ivity, whereas the silanes led to cis-2,5-dialkylpyrrolidines with moderate stereoselectivity. (C) 1999 Elsevier Science Ltd. All rights reserved.