Prev. Article Next Article Table of Contents

Communication

Platinum- and Gold-Catalyzed Cycloisomerization Reactions of Hydroxylated Enynes

Supporting Info

Victor Mamane, Tobias Gress, Helga Krause, and Alois Fürstner*

Max-Planck-Institut fr Kohlenforschung, D-45470 Mlheim/Ruhr, Germany

J. Am. Chem. Soc., 2004, 126 (28), pp 8654–8655

DOI: 10.1021/ja048094q

Publication Date (Web): June 25, 2004

In papers with more than one author, the asterisk indicates the name of the author to whom inquiries about the paper should be addressed.

, fuerstner@mpi-muelheim.mpg.de

Abstract

Exposure of enynes containing a hydroxyl group at one of the propargylic positions to catalytic amounts of either PtCl₂ or (PPh₃)AuCl/AgSbF₆ results in a selective rearrangement with formation of bicyclo[3.1.0]hexan-3-one derivatives. The same products are obtained by a “one-pot” process on treatment of an alkynal with allylchlorodimethylsilane (4) and PtCl₂ via a reaction cascade involving an initial platinum-catalyzed allylation followed by the cycloisomerization of the homoallylic alcohol formed in situ. This novel skeletal reorganization process was implemented into a concise total synthesis of the terpenes sabinone (18) and sabinol (19). Furthermore it is shown that conversion of the hydroxylated enynes into the corresponding acetates followed by reaction with a cationic gold catalyst formed from (PPh₃)AuCl and AgSbF₆ opens entry into isomeric products bearing the ketone function at the C-2 position of the bicyclo[3.1.0]hexane skeleton. The outcome of a deuterium labeling experiment and the analysis of the stereochemical course of the cycloisomerization reaction are consistent with the formation of cyclopropylmethyl platinum carbene species as reactive intermediates.

View: Full Text HTML | Hi-Res PDF