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Synthesis 2010(17): 2957-2964  
DOI: 10.1055/s-0030-1258161
PAPER
© Georg Thieme Verlag Stuttgart ˙ New York

Expeditious Synthesis of Functionalized Piperidines by Regioselective Ring Opening of Aziridines by Enals Catalyzed by an N-Heterocyclic Carbene

Santosh Singha, Vijai K. Raia,b, Pankaj Singha, Lal Dhar S. Yadav*a
a Green Synthesis Lab, Department of Chemistry, University of Allahabad, Allahabad 211 002, India
Fax: +91(532)2460533; e-Mail: ldsyadav@hotmail.com;
b College of Science, Shri Mata Vaishno Devi University, Katra, Jammu & Kashmir 182 320, India
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Publication History

Received 19 April 2010
Publication Date:
07 July 2010 (online)

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Abstract

A novel, expeditious, and diastereoselective synthesis of 2,6-disubstituted piperidin-4-ones is reported. Regioselective ring opening catalyzed by an N-heterocyclic carbene (NHC) of terminal aziridines by enals affords β′-amino α,β-unsaturated ketones, which on intramolecular aza-Michael addition in the presence of potassium carbonate furnish 2,6-disubstituted piperidin-4-ones cis-selectively, in excellent yields (83-95%). The protocol involves carbonyl umpolung reactivity of enals, in which the carbonyl carbon nucleophilically attacks the electrophilic terminal aziridines. The absence of byproduct formation, operational simplicity, the use of ambient temperature, high yields, and regio- and diastereoselectivity are the salient features of this procedure.

Key words

N-heterocyclic carbenes - aziridines - umpolung - enals - aza-Michael addition - piperidines