The influence of proton-donor solvent on [4+2] benzannulation reaction of dienal with tertiary enaminone

The [4+2] benzannulation synthesis of benzaldehyde derivative containing an electron withdrawing group at the C3 position by using the dienal and tertiary enaminone is the practical method recently, which can only be carried out in protic organic solvent. Here, the quantum chemical calculation indicates that the solvent molecule plays the vital role of proton donor which can significantly decrease the activation energy and accordingly increase the reaction speed or trend. This study provides a novel understanding for the effect of solvent environment on reaction mechanism.