THEORETICAL INVESTIGATION ON THE REACTION MECHANISM OF CuI-CATALYZED FORMATION OF ETHYL 2-PHENYLACETOACETATE
Abstract
The reaction mechanism of CuI-catalyzed formation of ethyl 2-phenylacetoacetate by arylation of ethyl acetoacetate has been investigated by density functional theory (DFT) using Becke's three-parameter nonlocal exchange functional and the Lee, Yang, and Parr nonlocal correlation functional (B3LYP). The geometries of the reactants, intermediates, transition states, and products have been optimized and verified by means of vibration frequency calculations. According to our assumption, this reaction can be divided into two stages. The rate-determining step is found to be the 3 → 4-TS procedure, which is the first procedure of stage 1. The low energy barrier of 39.85 kcal/mol indicates that this reaction can be carried out, which is in accordance with the experimental facts. For comparison, we have investigated the reaction mechanism of the same chemical reaction without CuI catalyst, whose energy barrier of rate-determining step is 212.76 kcal/mol higher than that with CuI catalyst. This fact suggests that CuI catalyst accelerates the reaction by remarkably lowering the energy barrier. The solvation effects on the barriers of the reaction are important. But the energetic order in DMSO solvent seems to be almost the same as that in gas-phase, which indicates that our conclusion achieved in gas-phase is believable. Our findings reveal the microscopic catalytic mechanism of CuI and are in agreement with the experimental facts.
