One-Pot Synthesis of 2-(Het)aryl/alkyl-3-cyanobenzofurans from 2-(2-Bromoaryl)-3-(het)aryl-3-(methylthio)acrylonitriles and Benzyl Carbamate

Abstract

A one-pot synthesis of 2-(het)aryl/alkyl-3-cyanobenzofurans has been reported. The overall sequence involves base-induced reaction of 2-(2-bromoaryl)-3-(het)aryl-3-(methylthio)acrylonitriles with benzyl carbamate, generating α-(het)aroyl-α-(2-bromoaryl)acetonitriles, which are in situ subjected to copper-catalyzed intramolecular O -arylation, furnishing the 2-(het)aryl/alkyl-3-cyanobenzofurans in high yields. A probable mechanism for the base-induced cleavage of 2-(2-bromoaryl)-3-(het)aryl-3-(methylthio)acrylonitriles to α-(het)aroyl-α-(2-bromoaryl)acetonitriles in the presence of benzyl carbamate has been proposed.

Single-Pot Preparation of 4-Amino-2-(het)aryl-5-Substituted Thiazoles Employing Functionalized Dithioesters as Thiocarbonyl Precursors

“…Since the past few years, we have been exploring newly designed organosulfur intermediates − which are readily obtained by the condensation of the appropriate active methylene derivatives with functionalized dithioesters in the presence of base, followed by alkylation of the generated enethiolate intermediates. By utilizing these precursors, we have developed new synthetic routes for a variety of (het)­aryl/alkylsubstituted, sulfur containing, as well as sulfur-free five membered heterocycles, , such as pyrazoles, isoxazoles, oxazoles, imidazoles, thiophenes, thiazoles, and the corresponding benzo/heterofused analogues, i.e., indoles, , benzothiophenes, ,, and benzofurans .…”