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Asymmetric [3,3]- and [1,3]-Sigmatropic Rearrangements of γ-Allyloxy Vinylogous Urethanes

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journal contribution
posted on 17.09.2009, 00:00 by Yu-Jang Li, Yuan-Kang Chang, Guo-Ming Ho, Hua-Ming Huang
Vinylogous urethanes derived from condensation of prolinol or prolinol tert-butyldimethylsilyl ether with 4-allyloxyketoester were found to undergo a thermal [3,3]-sigmatropic rearrangement, providing compounds with N-substituted quaternary carbon centers. Cyclizations (subsequently or in situ) of the rearranged products generated hexahydro-3,4-dioxa-8a-aza-as-indacen-2-ones. Various terminally substituted allyloxy ketoesters and arylmethoxy ketoesters were found to generate tricyclic compounds via [1,3]-sigmatropic rearrangement. Finally, tricyclic lactones were transformed successfully into lactams.