Ring closing alkyne metathesis: stereoselective synthesis of civetone

A concise and stereoselective synthesis of the macrocyclic musk civetone 6 is reported starting from readily available 9-undecynol. The key steps comp rise a ring closing metathesis of diyne 4 followed by Lindlar reduction of the resulting cycloalkyne 5. The cyclization can be effected either by usin g catalytic amounts of the Schrock alkylidyne complex (t-BuO)(3)W drop CCMe 3 or by means of an in situ catalyst mixture generated from Mo(CO)(6) and p -trifluoromethylphenol. Both catalyst systems turned out to be compatible w ith the unprotected ketone function of the substrate. (C) 2000 Elsevier Sci ence S.A. All rights reserved.