Computational Study on the Aminolysis of β-Hydroxy-α,β-Unsaturated Ester via the Favorable Path Including the Formation of α-Oxo Ketene Intermediate

The possible mechanisms of the aminolysis of N-methyl-3-(methoxycarbonyl)-4-hydroxy-2-pyridone (β-hydroxy-α,β-unsaturated ester) with dimethylamine are investigated at the hybrid density functional theory B3LYP/6-31G(d,p) level in the gas phase. Single-point computations at the B3LYP/6-311++G(d,p) and the Becke88-Becke95 1-parameter model BB1K/6-311++G(d,p) levels are performed for more precise energy predictions. Solvent effects are also assessed by single-point calculations at the integral equation formalism polarized continuum model IEFPCM-B3LYP/6-311++G(d,p) and IEFPCM-BB1K/6-311++G(d,p) levels on the gas-phase optimized geometries. Three possible pathways, the concerted pathway (path A), the stepwise pathway involving tetrahedral intermediates (path B), and the stepwise pathway via α-oxo ketene intermediate due to the participation of β-hydroxy (path C), are taken into account for the title reaction. Moreover, path C includes two sequential processes. The first process is to generate α-oxo ketene int...