Intermediates in Ruthenium-Catalyzed Olefin Metathesis

Hong SH, Day MW, Grubbs RH. Decomposition of a Key Intermediate in Ruthenium-Catalyzed Olefin Metathesis Reactions. J Am Chem Soc. 2004 126(24) 7414-7415. 

Ruthenium-catalyzed olefin cross-metathesis (ring-closing metathesis, RGM) between terminal alkenes and vinyl-boronic acid or esters has recently been developed for the synthesis of ( )-l-alkenylboron compounds from alkenes.459,460 The efficiency of protocol was proved in the synthesis of a key intermediate of epothilone 490 292 461 (Equation (84)). The vinyl boronate was given almost exclusively the trans-adduct. 

Copper(I) triflate was used as a co-catalyst in a palladium-catalyzed carbonylation reaction (Sch. 27). The copper Lewis acid was required for the transformation of homoallylic alcohol 118 to lactone 119. It was suggested that the CuOTf removes chloride from the organopalladium intermediate to effect olefin complexation and subsequent migratory insertion [60]. Copper(I) and copper(II) chlorides activate ruthenium alkylidene complexes for olefin metathesis by facilitating decomplexation of phosphines from the transition metal [61]. 

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