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Synthesis 2004(6): 0949-0959  
DOI: 10.1055/s-2004-822332
PAPER
© Georg Thieme Verlag Stuttgart · New York

Inverse Electron Demand Diels-Alder Reactions of Heterodienes Catalyzed by Potassium Hydrogen Sulfate: Diastereoselective, One-Pot Synthesis of Pyranobenzopyrans, Furanobenzopyrans and Tetrahydroquinolines Derivatives

R. Senthil Kumar, Rajagopal Nagarajan, Paramasivan T. Perumal*
Organic Chemistry Division, Central Leather Research Institute, Adyar, Chennai - 600 020, India
Fax: +91(44)24911589; e-Mail: ptperumal@hotmail.com;
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Publication History

Received 3 November 2003
Publication Date:
13 April 2004 (online)

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Abstract

Potassium hydrogen sulfate catalyzes the one-pot three components coupling of aldehydes, anilines, and electron rich dienophiles such as dihydropyran, dihydrofuran, ethyl vinylether, and cyclopentadiene. With o-hydroxybenzaldehyde, the reaction probably proceeds through the formation of o-quinonemethide intermediate, which subsequently undergoes cycloaddition with cyclic and acyclic enol ethers leading to the formation of respective chromanes. However, in case of benzaldehydes with no o-hydroxy group, the imine formed acts as the heterodiene and leads to the formation of tetrahydroquinolines.

Keywords

heterodienes - potassium hydrogen sulfate - pyranobenzopyrans - furanobenzopyrans - tetrahydroquinolines