Ring-chain tautomerism in organic synthesis: synthesis of heterocyclic enamines from a novel and practical formal ring transformation reaction of lactones.
A novel approach to heterocyclic enamines has been developed from the formal ring transformation reaction of lactones. The synthesis comprises consecutive Reformatsky reaction of lactones and mesylation of the resulting mixture of ring-chain tautomers in a one-pot reaction, followed by cyclocondensation reaction with primary amines. The synthetic application of this method was demonstrated by a straightforward preparation of indolizidine compounds via N-(3-bromopropyl)-substituted enamine intermediates. The use of cheap and readily available materials and reagents under very mild conditions renders this formal ring transformation method practical and applicable in the preparation of various heterocyclic enamines that are the precursors for (poly)hydroxylated alkaloid derivatives.
Wang
Mei-Xiang
MX
Laboratory of Chemical Biology, Center for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China. mxwang@mail.iccas.ac.cn
Liu
Yong
Y
Gao
Hong-Yun
HY
Zhang
Yan
Y
Yu
Chu-Yi
CY
Huang
Zhi-Tang
ZT
Fleet
George W J
GW