C–H Bond Activation by Ruthenium(0) Complexes. Isolation of an Active Intermediate in the Ruthenium Catalyzed Aldol and Michael Reactions

Carbon-hydrogen bond oxidative addition of alkyl cyanoacetate to Ru(C2H4)(PPh3)3 in benzene at room temperature gives mer-RuH(NCCHCOOR)(NCCH2COOR)(PPh3)3 (R = Me, Et) accompanied by the liberation of ethylene. X-Ray structure analysis of the THF adduct (R = Me) reveals that NCCHCOOMe group bonds to ruthenium not through the methine carbon but the cyano group. These complexes react with benzaldehyde and methyl iodide to give alkyl (E)-1-cyanocinnamate and alkyl 2-cyanopropionate, respectively.