The fast and efficient KI/H2O2 mediated 2-sulfonylation of indoles and N-methylpyrrole in water.

Jun Zhang,Ping Liu,Yan Liu,Zhong Wang,Bin Dai,Lingjuan Chen

doi:10.1039/c8ra09367a

Abstract

The rapid and efficient KI/H2O2-mediated 2-sulfonylation of substituted indoles and N-methylpyrrole was established. The corresponding 2-sulfonylation products are synthesized from readily available sulfur sources, namely arylsulfonyl hydrazides, 4-methylbenzenesulfinic acid and sodium 4-methylbenzenesulfinate in good to excellent yields in only 5 min. Moreover, the aqueous solution of hydrogen peroxide is used as both oxidant and solvent. Mechanistic studies demonstrated that 2,3-diiodoindoline was the main sulfonylation intermediate.

Highlights

Indole is a widely used building block and is found in many natural products, pharmaceuticals and ne chemicals.1 2-Sulfonylindoles are an important class of indole derivatives due to the sulfonyl moiety which can enhance bioactivity[2] and acts as a useful vehicle for the development of new strategies for synthesis.[3]
A series of simple, efficient and direct 2-sulfonylations of indoles with sodium sul nates have been reported for the synthesis of 2-arylsulfonyl indoles
Barman and co-workers reported the elegant sulfonylation of sulfonyl hydrazides and indoles using TBHP/I2 as the catalyst and DCE as solvent.[11]

Summary

Introduction

Indole is a widely used building block and is found in many natural products, pharmaceuticals and ne chemicals.1 2-Sulfonylindoles are an important class of indole derivatives due to the sulfonyl moiety which can enhance bioactivity[2] and acts as a useful vehicle for the development of new strategies for synthesis.[3]. By increasing the KI content to 20%, and with the slow addition of 30% H2O2 solution to the reaction, we found that the 2-sulfonylation of indole can occur rapidly resulting in 53% yield of product 3a in only 5 min (entry 3).

Results

Conclusion