Imines, RCH=N-ZH, possessing a range of ZH groups (Z=CHCOPh, CHCOSR, CHCONHR, CHP(O)(OEt)2, 2-CH-pyridyl, 2-CH-thiazolyl, and 9-fluorenyl) undergo thermal 1,2-prototropy generating azomethine ylides stereospecifically. The intermediate azomethine ylides undergo cycloaddition reactions with dipolarophiles either via an endo-transition state or via both endo- and exo-transition states to give polyfunctional pyrrolidines in good yield. In certain instances involving imines in which the amide activating group is present, the imine catalyses cis ⇌ trans isomerisation of the dipolarophile. X-Ray crystal structures of two of the cycloadducts are reported.
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ASJC Scopus subject areas
- Drug Discovery
- Organic Chemistry