Chemistry Department, University of Alberta, Edmonton, Alberta, Canada T6G 2G2.
Org Biomol Chem. 2009 Dec 7;7(23):4862-70. doi: 10.1039/b914580j. Epub 2009 Sep 30.
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 beta-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.
易于获得的 3-烷氧羰基-6-羟基-5-卤代香豆素可以通过一系列反应转化为 4-卤代-5-羟基吲哚，其关键步骤是共轭还原或共轭加成、脱羧、氨开环内酯、酚氧保护、Hofmann 重排为 N-Boc 乙胺、氧化为醌和脱氮保护。所得的β-氨基乙基醌环化生成醌亚胺和吲哚的混合物，亚胺在氧化铝上用铑处理或自发异构化为吲哚。
