One-pot synthesis of pyrroles using a titanium-catalyzed multicomponent coupling procedure

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• 作者：Cody M. Pasko ; Amila A. Dissanayake ; Brennan S. Billow ; Aaron L. Odom ; ^{odom@chemistry.msu.edu" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Pyrrole ; Catalysis ; Multicomponent reaction ; Titanium
• 刊名：Tetrahedron
• 出版年：2016
• 出版时间：3 March 2016
• 年：2016
• 卷：72
• 期：9
• 页码：1168-1176
• 全文大小：1448 K

文摘

A simple one-pot procedure for the production of 2-carboxylpyrroles with 4-alkyl, 5-alkyl, 4-aryl, 4-aryl-5-alkyl, or 3,4-diaryl substitution patterns is presented. The procedure involves the titanium-catalyzed multicomponent coupling of alkynes, primary amines and isonitriles to give 1,3-diimines in situ; the multicomponent product is then treated with the ethyl ester of glycine hydrochloride to give the NH-pyrrole. The reaction can be carried out with the neutralized glycine ester or with the hydrochloride salt using DBU as a base. Yields of pyrrole based on starting alkyne varied from 25 to 65% over the one pot procedure, and in most cases only one regioisomer of the product is observed. Further, it is proposed that the regioselectivities of the reactions are a result of rate-determining ring closure after relatively fast transimination with glycine ethyl ester.