Synthesis 2008(7): 1039-1044  
DOI: 10.1055/s-2008-1032126
PAPER
© Georg Thieme Verlag Stuttgart · New York

New Findings on the Cerium(IV) Ammonium Nitrate Catalyzed Povarov Reaction: Stereoselective Synthesis of 4-Alkoxy-2-aryl-1,2,3,4-tetrahydro­quinoline Derivatives

Vellaisamy Sridharan, Carmen Avendaño, J. Carlos Menéndez*
Departamento de Química Orgánica y Farmacéutica, Facultad de Farmacia, Universidad Complutense, 28040 Madrid, Spain
Fax: +34(91)3941822; e-Mail: josecm@farm.ucm.es;
Further Information

Publication History

Received 18 October 2007
Publication Date:
06 March 2008 (online)

Abstract

Cerium(IV) ammonium nitrate catalyzes the three-component, imino Diels-Alder (Povarov) reaction between anilines, aromatic aldehydes, and acyclic vinyl ethers, giving cis-4-alkoxy-2-aryl-1,2,3,4-tetrahydroquinolines with almost complete diastereoselectivity. The corresponding reaction starting from cyclic vinyl ethers gave the two possible diastereomers, with the endo-compound as the major product. This stereochemical outcome is explained through a stepwise mechanism for the imino Diels-Alder reaction, and this mechanism was subsequently proved by trapping the putative oxonium intermediate in the presence of ethanol.

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For a preliminary communication of a CAN-catalyzed vinylogous Povarov reaction involving α,β-unsaturated aldehydes, see ref. 16k.