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Paper | Regular issue | Vol 78, No. 5, 2009, pp.1243-1252
Published online, 23rd January, 2009
DOI: 10.3987/COM-08-11620
Synthesis of Homoproline Analogues Containing Heterocyclic Rings and Their Activity as Organocatalysts for Michael Reaction

Efrosini Barbayianni, Paola Bouzi, Violetta Constantinou-Kokotou, Valentine Ragoussis, and George Kokotos*

*Laboratory of Organic Chemistry, Department of Chemistry, University of Athens, Panepistimiopolis, Athens 15771, Greece

Abstract

Two homoproline derivatives containing either the 5-thioxo-1,2,4-oxadiazole or the 2-oxo-1,2,3,5-oxathiodiazole bioisosteric groups, in replacement of the carboxyl group, were synthesized and their catalytic activities in Michael reactions were evaluated. The derivative containing the 5-thioxo-1,2,4-oxadiazole ring outperforms proline in the context of enantioselectivity in the reactions between β-nitrostyrene and acetone or cyclohexanone, indicating that the conversion of the carboxylic group of homoproline to a bioisosteric heterocyclic ring leads to a superior organocatalyst.