Synlett 2017; 28(12): 1473-1477
DOI: 10.1055/s-0036-1588172
letter
© Georg Thieme Verlag Stuttgart · New York

A Nucleophilic Activation of Carboxylic Acids by Proline: Oxa-Michael Addition to Methyl Vinyl Ketone under Solvent-Free Conditions

Ajit Kumar Jha, Heena Inani, Srinivasan Easwar*
  • Department of Chemistry, Central University of Rajasthan, NH-8, Bandarsindri, Distt. Ajmer, Rajasthan 305817, India   Email: easwar.srinivasan@curaj.ac.in
Further Information

Publication History

Received: 07 February 2017

Accepted after revision: 17 March 2017

Publication Date:
10 April 2017 (eFirst)

Abstract

A serendipitous nucleophilic activation of carboxylic acids by proline helped to achieve a direct hydrocarboxylation of methyl vinyl ketone at 60 °C under solvent-free conditions. A variety of carboxylic acids were used successfully in this oxa-Michael addition, affording useful 4-acyloxy-2-butanones in moderate yields. The reactions are carried out under solvent-free conditions, and the products are isolated in high purity by a simple work-up procedure without any need for column chromatographic purification, imparting a green quotient to the protocol. A heterodimeric non-covalent interaction between the amino acid and the carboxylic acid appears to be the most plausible mechanistic interpretation for the nucleophilic activation; additionally, the possible activation of the Michael acceptor by iminium ion formation presents an interesting case of proline acting as a bifunctional catalyst.

Supporting Information