Ruthenium Vinylidenes and Allenylidenes in Catalysis

Abstract

During the last decade, ruthenium catalysis, including asymmetric catalysis, has attracted increasing interest owing to its wide range of applications in organic synthesis [T. Naota, H. Takaya, S.I. Murahashi (1998) Chem. Rev. 98:2599; B.M. Trost, F.D. Toste, A.B. Pinkerton (2001) Chem. Rev. 101:2067; B.M. Trost BM (2002) Acc. Chem. Res. 35:695]. Ruthenium complexes bearing a carbenic ligand, such as a carbene, a vinylidene or an allenylidene group have found useful applications for selective transformations of unsaturated substrates. After the discovery of the first ruthenium vinylidene complex by Bruce at the end of the 1970s [M.I. Bruce, R.C. Wallis (1978) J. Organomet. Chem. 161:C1; M.I. Bruce, A.G. Swincer, R.C. Wallis (1979) J. Organomet. Chem. 171:C5], the impact of these reactive species, easily generated from terminal alkynes, became obvious in catalysis, and led to the development of new selective transformations of alkynes, most of them with atom economy [C. Bruneau, P.H. Dixneuf (1999) Acc. Chem. Res. 32:311]. Their advantages include the unusual regioselectivity of additions to alkynes. A few years later, the adventure of ruthenium allenylidene derivatives started when their straightforward preparation via activation/dehydration of propargylic alcohols at selected ruthenium centres was demonstrated [J.P. Selegue (1982) Organometallics 1:217; J.P. Selegue (1983) J. Am. Chem. Soc. 105:5921]. Their involvement in catalysis is currently leading to a variety of unprecedented reactions from propargylic compounds. Recent results on transformations of alkynes with ruthenium vinylidenes and allenylidenes as postulated active species in catalytic reactions will be presented. The use of these unsaturated species as catalyst precursors for other types of reactions will also be reported.