Abstract

Reactions of 2-methylfuran and thiophene with readily available N-acylbenzotriazoles (RCOBt, where R = 4-tolyl, 4-methoxyphenyl, benzyl, 4-nitrophenyl, 4-diethylaminophenyl, 2-pyridyl and 1-naphthyl) in the presence of TiCl 4 or ZnBr 2 produced 2-methyl-4-acylfurans 2a-e and 2-acylthiophenes 3a-f in average yields of 54 % and 75 %, respectively. Literature yields for the preparation of the same compounds are significantly lower.

Highlights

  • We recently described the C-acylation of pyrroles and indoles using N-acylbenzotriazoles in the presence of TiCl4 under mild conditions to give high yields of isomerically pure 2- and 3-acylated pyrroles and 3-acylated indoles

  • As part of our continuing interest in the chemistry of Nacylbenzotriazoles, we describe here analogous C-acylations of 2-methylfuran and thiophene

  • Some Friedel-Crafts reactions of furans and thiophenes are complicated by the high reactivity of these heterocyclic rings under strong Lewis acid conditions

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Summary

Introduction

We recently described the C-acylation of pyrroles and indoles using N-acylbenzotriazoles in the presence of TiCl4 under mild conditions to give high yields of isomerically pure 2- and 3-acylated pyrroles and 3-acylated indoles. As part of our continuing interest in the chemistry of Nacylbenzotriazoles, we describe here analogous C-acylations of 2-methylfuran and thiophene. We recently described the C-acylation of pyrroles and indoles using N-acylbenzotriazoles in the presence of TiCl4 under mild conditions to give high yields of isomerically pure 2- and 3-acylated pyrroles and 3-acylated indoles.. As part of our continuing interest in the chemistry of Nacylbenzotriazoles, we describe here analogous C-acylations of 2-methylfuran and thiophene. Some Friedel-Crafts reactions of furans and thiophenes are complicated by the high reactivity of these heterocyclic rings under strong Lewis acid conditions.. Syntheses of acylthiophenes have been reported using carboxylic acid chlorides and catalysis with AlCl33 and SnCl4.4 Other reported methods for C-acylation of furans and thiophenes require special reagents and/or give low to moderate yields.. We apply readily available N-acylbenzotriazoles for C-acylations of 2-methylfuran and thiophene in good to excellent yields in the presence of the relatively mild Lewis acids, TiCl4 or ZnBr2.

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