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Pure Appl. Chem. Vol. 74, No. 8, pp. 1339-1347 (2002)

Pure and Applied Chemistry

Vol. 74, Issue 8

Alkaloid synthesis via [3+2] cycloadditions*

William H. Pearson

Department of Chemistry, University of Michigan, Ann Arbor, MI, 48109-1055, USA

Abstract: Tin-lithium exchange on (2-azaallyl)stannanes affords nonstabilized 2-azaallyllithiums (2-azaallyl anions) that undergo [p4s+p2s] cycloadditions with alkenes to afford pyrrolidines. The scope of this method has been expanded to include 2-azapentadienyllithiums and heteroatom-substituted 2-azaallyllithiums. Alternatively, the (2-azaallyl)stannanes may also be used to generate nonstabilized azomethine ylides via N-alkylation/destannylation or N-protonation/destannylation, and these ylides were also found to be useful for the synthesis of pyrrolidines by [p4s+p2s] cycloadditions with alkenes. Applications of both methods to the total synthesis of alkaloids such as (+)-coccinine, lepadiformine stereoisomers, lapidilectine B, and indolizidine 239CD have been accomplished.

* Plenary lecture presented at the 3rd Florida Conference on Heterocyclic Chemistry (FloHet-III), Gainesville, Florida, USA, 6-8 March 2002. Other lectures are published in this issue, pp. 1317–1368.


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