Origin of regioselectivity in the reactions of nitronate and enolate ambident anions.

The reactions of nitronates of ring-substituted phenylnitromethanes and enolates of ring-substituted 1-phenyl-2-propanones with MeOBs gave exclusively the O-methylated and C-methylated products, respectively. DFT calculations suggested that two factors, namely, intrinsic barriers and metal-cation coordination, control the C/O selectivity. The kinetic preference for O-methylation in the reactions of nitronates arises from the intrinsic barriers, which are ca.

Kinetic study of proton-transfer reactions of phenylnitromethanes. Implication for the origin of nitroalkane anomaly.

Measurements of rate constants and substituent effects for three important elementary steps of proton-transfer reactions of phenylnitromethane were reported. The Hammett ρ values for the deprotonation of ArCH(2)NO(2) with OH(-), protonation of ArCH═NO(2)(-) with H(2)O, and protonation of ArCH═NO(2)(-) with HCl were determined in aqueous MeOH at 25 °C. Comparison of these experimentally observed ρ values with those calculated at B3LYP/6-31G* revealed that aci-nitro species (ArCH═NO(2)H), which is formed on the O-protonation of ArCH═NO(2)(-), does not lie on the main route of the proton-transfer reaction.