Smart ruthenium catalysts for the selective catalytic transformations of alkynes

Abstract

Easy to produce and to handle ruthenium catalyst precursors have been used for the activation of a variety of terminal alkynes. The anti-Markovnikov addition is performed in the catalytic synthesis of vinylcarbamates from terminal alkynes, CO2 and secondary amines via ruthenium vinylidene species, with catalysts of type RuCl2(PR3)(arene) (A) and that of carboxylic acids to alkyl-C≡CH, aryl-C≡CH, HC≡C-C(Me)=CH2 and HC≡C-CH=CHOMe is performed by catalyst Ru(η3-CH2C(Me)CH2)2(Ph 2P(CH2)nPPh2) F4 (n = 4) to produced (Z)-alken-1-yl esters, whereas the use of catalyst F2 (n = 2) is necessary to reach high regioselectivity in the formation of (Z)-alken-1-yl esters from HC≡C-SiMe3 and HC≡CCR2OMe. By contrast the latter (F2) allows the isomerisation of HC≡CCR2OH compounds into unsaturated aldehydes O=CH-CH=CR2 and the reaction is shown to proceed via an anti-Markovnikov adduct. The use of electron-rich complex, containing a labile (cod) ligand, RuCl(cod)(C5Me5) (G) offers the regioselective coupling C-Cof allyl alcohol with alkynes to produce γ,δ-unsaturated aldehydes and with propargylic alcohols to afford 5-methylene tetrahydropyrane derivatives.