The coumarin→indole transformation—a method for preparing 4-halo-5-hydroxyindoles from coumarins
作者:Elia J. L. Stoffman、Derrick. L. J. Clive
DOI:10.1039/b914580j
日期:——
Readily accessible 3-alkoxycarbonyl-6-hydroxy-5-halocoumarins can be converted into 4-halo-5-hydroxyindoles by a sequence whose essential steps are conjugate reduction or conjugate addition, decarboxylation, lactone opening with ammonia, phenolic oxygen protection, Hofmann rearrangement to an N-Boc ethylamine, oxidation to a quinone and deprotection of the nitrogen. The resulting β-aminoethyl quinone cyclizes to a mixture of quinone imine and indole, and the imine tautomerizes to the indole spontaneously or on treatment with rhodium on alumina.
readily accessible 3-烷氧羧基-6-羟基-5-卤代香豆素可以通过一系列步骤转化为4-卤代-5-羟基吲哚,主要步骤包括共轭还原或共轭加成、脱羧、与氨的内酯开环、酚氧保护、霍夫曼重排为N-Boc乙胺、氧化为醌及氮的去保护。生成的β-氨基乙基醌环化为醌亚胺和吲哚的混合物,亚胺可以自发或在铝土矿上的铑处理下转化为吲哚。