Computational study on the aminolysis of beta-hydroxy-alpha,beta-unsaturated ester via the favorable path including the formation of alpha-oxo ketene intermediate.
The possible mechanisms of the aminolysis of N-methyl-3-(methoxycarbonyl)-4-hydroxy-2-pyridone (beta-hydroxy-alpha,beta-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 alpha-oxo ketene intermediate due to the participation of beta-hydroxy (path C), are taken into account for the title reaction. Moreover, path C includes two sequential processes. The first process is to generate alpha-oxo ketene intermediate via the decomposition of N-methyl-3-(methoxycarbonyl)-4-hydroxy-2-pyridone; the second process is the addition of dimethylamine to alpha-oxo ketene intermediate. Our results indicate that path C is more favorable than paths A and B both in the gas phase and in solvent (heptane). In path C, the first process is the rate-determining step, and the second process is revealed to be a [4+2] pseudopericyclic reaction without the energy barrier. Being independent of the concentration of amine, the first process obeys the first-order rate law.
Jin
Lu
L
College of Chemistry, Sichuan University, Chengdu 610064, PR China.
Xue
Ying
Y
Zhang
Hui
H
Kim
Chan Kyung
CK
Xie
Dai Qian
DQ
Yan
Guo Sen
GS
D000588:Amines / Q000737:chemistry*; D003198:Computer Simulation; D004123:Dimethylamines / Q000737:chemistry; D004952:Esters / Q000737:chemistry*; D005030:Ethylenes / Q000737:chemistry*; D006536:Heptanes / Q000737:chemistry; D007659:Ketones / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D011728:Pyridones / Q000737:chemistry*; D011789:Quantum Theory; D012997:Solvents / Q000737:chemistry
D000588:Amines; D004123:Dimethylamines; D004952:Esters; D005030:Ethylenes; D006536:Heptanes; D007659:Ketones; C529849:N-methyl-3-(methoxycarbonyl)-4-hydroxy-2-pyridone; D011728:Pyridones; D012997:Solvents; C034516:dimethylamine; C008223:ketene