A molecular electron density theory study of polar Diels-Alder reaction between 2,4-dimethyl-5-ethoxyoxazole and ethyl 4,4,4-trifluorocrotonate

The mechanism and the selectivity of Diels-Alder (DA) reaction between 2,4-dimethyl-5-ethoxyoxazole (DE4) and ethyl 4,4,4-trifluorocrotonate (ET5) at 298 K in the presence of toluene have been theoretically reviewed by the molecular electron density theory (MEDT) with the computational level of MPWB1K/6-311G(d,p). In the DA reaction, the regioselectivity was studied at the reactive positions of the DE4and ET5through the studied nucleophilic and electrophilic Parr functions. The conceptual density functional theory (CDFT) reactivity indicated that ET5and DE4work as a strong electrophile and nucleophile, respectively. The energy profiles indicated that the transition stateTS1ngenerates a unique product corresponding cycloadduct (CA) ofCA1n, which is completely consistent with the experimental research. Theendostereoselectivity was confirmed by both results of molecular electrostatic potential (MEP) and the non-covalent interactions (NCIs) at the C1-C6 regioisomeric path. Electron localization function (ELF) and the intrinsic reaction coordinate (IRC) pathways were used to understand the mechanism of this DA reaction.

Automated summary

The mechanism and selectivity of the Diels-Alder reaction between DE4 and ET5 have been theoretically investigated, revealing that DE4 acts as a nucleophile and ET5 as an electrophile, generating a unique product consistent with experimental results.