Effect of substituents on the molybdenum mediated carbonylation and methoxycarbonylation of dihaloalkynes

Dihaloalkynes of the type YCH(R)Ctriple bond; length of mdashCCH(R)Y (Y = Cl, Br, I; R = H or Me) or YCMe2Ctriple bond; length of mdashCCMe2Y were prepared from their diol precursors and reacted with [Mo(CO)3(phen)Y]− (phen = 1,10-phenanthroline) in chlorinated solvent, methanol or water. Formation and stability of substituted products of the type [Mo(CO)2(η3-CH(R)C(COX)Cdouble bond; length as m-dashCH(R))(phen)Y] (X = Y or X = OMe) were found to be dependent upon the nature of the halogen and degree of alkyl substitution of the alkyne. Reactions carried out in mixtures of methanol and ethers gave an alternative double addition product of the type [Mo(CO)2(η3-CH(R)C(CO2Me)Cdouble bond; length as m-dashC(OMe)(CH2R))(phen)Y] for R = H, Y = Cl only.