Cathodic Cyclisation of N-(Oxoalkyl)pyridinium Salts − Formation of Tricyclic Indolizidine and Quinolizidine Derivatives in Aqueous Medium
作者:Jens Heimann、Hans J. Schäfer、Roland Fröhlich、Birgit Wibbeling
DOI:10.1002/ejoc.200300180
日期:2003.8
The cathodiccyclisation of N-(oxoalkyl)pyridiniumsalts, derived from 4-methylpyridine and cyclic ketones, afforded functionalised tricyclicindolizidine and quinolizidinederivatives in high yields. Through systematic variation of the ring size of the ketone and the cyclised ring, a series of four cyclopenta-/cyclohexa[a]indolizidines and -quinolizidines was obtained. The cyclisation was also applied
palladium-catalyzed Dowd–Beckwith ringexpansion/C–C bond formation cascade is described. A range of six to nine-membered β-alkenylated cyclic ketones possessing a quaternary carbon center were accessed under mild conditions. Besides styrenes, the electron-rich alkenes such as silyl enol ethers and enamides were also compatible, providing the desired β-alkylated cyclic ketones in moderate to good yields.