Synlett 2001; 2001(6): 0723-0732
DOI: 10.1055/s-2001-14578
account
© Georg Thieme Verlag, Rüdigerstr. 14, 70469 Stuttgart, Germany. All rights reserved. This journal, including all individual contributions and illustrations published therein, is legally protected by copyright for the duration of the copyright period. Any use, exploitation or commercialization outside the narrow limits set by copyright legislation, without the publisher's consent, is illegal and liable to criminal prosecution. This applies in particular to photostat reproduction, copying, cyclostyling, mimeographing or duplication of any kind, translating, preparation of microfilms, and electronic data processing and storage.

Catalysis of the Michael Reaction and the Vinylogous Michael Reaction by Ferric Chloride Hexahydrate

Jens Christoffers*
  • *Institut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany; Fax + 49 (0)711/685 4269; E-mail: jchr@po.uni-stuttgart.de
Weitere Informationen

Publikationsverlauf

Publikationsdatum:
31. Dezember 2001 (online)

Ferric chloride hexahydrate catalyzes the Michael reaction of 1,3-dicarbonyl compounds with α,β-unsaturated ketones under mild and non-basic conditions with extraordinary efficiency. The chemoselectivity of this Fe(III)-catalyzed process is superior to that of the classic base-mediated Michael reaction, since the latter suffers from various side and subsequent reactions, namely drawbacks such as aldol cyclizations and retro-Claisen reactions. Excellent yields and chemoselectivities together with the environmentally friendly nature of the Fe(III) catalysis make this an important alternative to established methods. An enone-dienol tautomerization of 2-acceptor substituted cycloalkenones is the precondition for the iron-catalyzed vinylogous Michael reaction. Herein a γ-donor formally undergoes conjugate addition to a β-acceptor to furnish products with 1,7-dioxo constitutions. Actually, this process is a sequence initiated by the tautomerization followed by a [4 + 2]-cycloaddition and a retro-aldol reaction. When benzoquinone derivatives are employed as acceptors, the products of the vinylogous Michael reactions are highly functionalized biaryl precursor compounds.