Synthesis 2010(17): 2901-2914  
DOI: 10.1055/s-0030-1258207
SPECIALTOPIC
© Georg Thieme Verlag Stuttgart ˙ New York

Microwave-Assisted Domino Hydroformylation/Cyclization Reactions: Scope and Limitations

Etienne Airiaua, Claire Chemina, Nicolas Girarda, Giacomo Lonzib, André Mann*a, Elena Petriccib, Jessica Salvadorib, Maurizio Taddei*b
a Laboratoire d’Innovation Thérapeutique, UMR 7200 CNRS-Université de Strasbourg, Faculté de Pharmacie, 74 route du Rhin, 67401 Illkirch, France
e-Mail: andre.mann@pharma.u-strasbg.fr;
b Dipartimento Farmaco Chimico Tecnologico, Università degli Studi di Siena, Via A. Moro 2, 53100 Siena, Italy
Fax: +39(0577)234280; e-Mail: taddei.m@unisi.it;
Further Information

Publication History

Received 13 April 2010
Publication Date:
13 August 2010 (online)

Abstract

Hydroformylation of alkenes can be carried out in short time and with low syngas pressure under microwave (MW) dielectric heating. Alkenes, carrying O-, N-, or C-nucleophilic fragments, can be designed for domino reactions, mainly cyclocondensations. Allyl and homoallyl alcohols are excellent substrates for cyclizative hydroformylation to lactols under MW heating. In the presence of NaOAc as an additional nucleophile, a domino reaction occurs giving 2-acetoxytetrahydrofurans, suitable to introduce a C-nucleophile on tetrahydrofuran rings through an oxocarbenium ion. The synthesis of the furanopiperidine substructure of cyclopamine is described as an application. With alkene amides, the domino process collapsed to a transient acyliminium ion that further cyclized with an additional C-nucleophile. To perform domino hydroformylation Pictet-Spengler or aza-Sakurai reactions, an autoclave under conventional heating is essential. Syntheses of (±)-epilupinine and of a homoberberine alkaloid are reported to illustrate each sequence. Although apparently more versatile, hydroformylation of alkenes using MW heating is sensitive to the nature of the nucleophiles present in the substrates, evidencing that the conventional heating process cannot be completely replaced by MW irradiation.

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http://www.cem.com/page163.html.

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http://www.anton-paar.com/001/en/60/262.

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In a 10 mL vial, the gas present under the reaction conditions is roughly 3 mmol for 1 mmol of substrate.