Allenylidene-Ruthenium Complexes as Alkene Metathesis Catalyst Precursors the First Evidence

Allenylidene-Ruthenium Complexes as Alkene Metathesis Catalyst Precursors the First Evidence 

The observation by Selegue in 1982 [13] that 16 electron ruthenium(II) intermediates could activate terminal propargyl alcohols into ruthenium-allenylidene complexes, via 3-hydroxyvinylidene-metal intermediates, showed not only thatthese allenylidene complexes were stable toward the action of the released water but, especially, that it could be an excellent way to generate allenylidene-metal complexes from easily accessible sources, the propargyl alcohols (Equation 8.1). 

This general route to a variety of allenylidene-metal complexes from propargyl alcohols, was demonstrated soon after for ruthenium) 11) complexes and for a large set of metal complexes [14—17]. 

This evidence of easy stoichiometric formation of ruthenium-allenylidene led Trost, 10 years later, to propose for the first time such an intermediate in a ruthenium (Il)-catalyzed transformation of functional propargyl alcohols [18[. Since 2000 Nishibayashi et al. [19-23] have developed a set of catalytic propargylations, with 

In the field of alkene metathesis ruthenium-allenylidene precursors have made, since 1998, an important contribution to catalysis [12, 31, 32], for the formation of cycles and macrocycles via RCM, ROMP and acyclic diene metathesis (ADMET) polymerization. 

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