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 cathodic cyclisation of N-(oxoalkyl)pyridinium salts, derived from 4-methylpyridine and cyclic ketones, afforded functionalised tricyclic indolizidine and quinolizidine derivatives 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
衍生自 4-甲基吡啶和环酮的 N-(氧代烷基)吡啶鎓盐的阴极环化以高产率提供了官能化的三环吲哚里西啶和喹唑啉衍生物。通过酮和环化环的环尺寸的系统变化,获得了一系列四种环戊二烯-/环六[a]吲哚里西啶和-喹啉二嗪。环化作用还用于合成环己 [b] 喹唑啉衍生物,它代表了鲸蜡基生物碱的亚结构。没有明显的替代路线像这种阴极环化这样的吲哚里西啶和喹尼西啶一样短。提出了环化的详细机制。在关键步骤中,由质子化酮还原生成的羟烷基可逆地加成到吡啶鎓环上。半经验计算表明,只能获得由热力学上更稳定的环化中间体产生的非对映异构体。从这些数据和环化过渡态的 ΔΔfH# 值来看,似乎更可能是热力学而不是动力学控制。(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)