Synthesis 2007(24): 3896-3906  
DOI: 10.1055/s-2007-990937
PAPER
© Georg Thieme Verlag Stuttgart · New York

Ring Opening and Rearrangement Reactions of Tricyclo[4.2.1.02,5]nonan-9-one

Ingbert Brauna, Florian Rudroffb, Marko D. Mihovilovicb, Thorsten Bach*a
a Lehrstuhl für Organische Chemie I, Technische Universität München, Lichtenbergstr. 4, 85747 Garching, Germany
Fax: +49(89)28913315; e-Mail: thorsten.bach@ch.tum.de;
b Institut für Angewandte Synthesechemie, Technische Universität Wien, Getreidemarkt 9/163-OC, 1060 Vienna, Austria
Further Information

Publication History

Received 26 September 2007
Publication Date:
28 November 2007 (online)

Abstract

A general concept is introduced to synthesize bicyclo[4.2.0]octanes by a sequence of intramolecular copper(I)-catalyzed [2+2] photocycloaddition and subsequent fragmentation reactions. The concept was tested by subjecting the photochemically accessible tricyclo[4.2.1.02,5]nonan-9-one to four different ring-opening or rearrangement reactions, which allowed for the formation of functionalized bicyclo[4.2.0]octanes by cleavage of the carbonyl bridge. All four methods investigated, Haller-Bauer cleavage, the Schmidt reaction, Baeyer-Villiger oxidation, and rhodium(II)-catalyzed rearrangement were applicable to tricyclo[4.2.1.02,5]nonan-9-one, but they differed with regard to enan­tioselectivity. Enzymatic Baeyer-Villiger oxidation was the most successful of these methods, also more successful than metal-catalyzed Baeyer-Villiger oxidation, providing access to enantiomerically enriched lactones, for example in 72% yield and 95% ee. The second-most successful method was with a commercially available rhodium catalyst, which effected ring enlargement of tricyclo[4.2.1.02,5]nonan-9-one to its homologue in good overall yield and modest enantioselectivity (up to 24% ee).