Hetero-intermolecular [2+2] photocycloaddition of 1,4-dihydropyridines: a combined experimental and DFT study

Abstract

In this article, the hetero-intermolecular [2+2] photocycloaddition of 1,4-dihydropyridines (1,4-DHPs) in solution was reported, wherein head-to-tail (HT) dimeric products (syn-dimers and cage dimers) were formed exclusively through successive inter- and intra-molecular [2+2] cycloaddition. The effects of irradiation wavelength, solvents and substituents on the efficiency of these transformations were investigated. To shed light on the intrinsic characteristics and stereoselectivity of the photocycloaddition, DFT and TDDFT theoretical calculations were carried out to reveal detailed reaction processes.