The one-pot synthesis of quinazoline-2,4-diones was developed in the presence of 4-dimethylaminopyridine (DMAP) by metal-free catalysis. The commercially available (Boc)₂O acted as a key precursor in the construction of the 2-position carbonyl of quinazolinediones. The p-methoxybenzyl (PMB)-activated heterocyclization could smoothly proceed at room temperature instead of the microwave condition. This strategy is compatible with a variety of substrates with different functional groups. Furthermore, this protocol was utilized to smoothly prepare Zenarestat with a total yield of 70%.

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.