Expedited microwave-assisted N-alkylation of isatins utilizing DBU

Abstract

The N-alkylation of a variety of isatins with alkyl or benzylic halides can be effected under microwave irradiation in ethanol using 1,8-diazabicyclo[5.4. 0]undec-7-ene (DBU) as a base. The conditions employed allow for the expedited synthesis of such substrates wherein the products precipitate from the reaction mixture in high yields and high purity after simple filtration. As will be described, microwave irradiation provides a relatively rapid means of effecting N-alkylations of isatin with a variety of benzylic halides, propargyl bromide and ethyl bromoacetate in times ranging from 10-25 min at 140 oC in closed vials. This report involves the first reported use of DBU for this purpose, and in contrast to other methods, allows for the facilitated isolation of pure products while avoiding extractive or chromatographic purification steps. © ARKAT-USA, Inc.