Photooxidation of 2,3-dihydroquinazolin-4(1H)-ones: retention or elimination of 2-substitution.

A series of mono and disubstituted 2,3-dihydroquinazolin-4(1H)-ones (DHQZs) were synthesized and the electronic and steric effects of the C2- and N3-substitutions on the retention or elimination of the C2-substitution by exposing them to the ultraviolet light were investigated. Electron transfer from photo-excited dihydroquinazolinones to chloroform solvent is proposed, in which both lone pairs on the N1- and N3-atoms can be involved in this process. The extent of the N1- and N3-atoms contributions in this electron-transfer process and also the retention or elimination of the C2-substitutions are dependent on the nature and steric hindrance of both C2- and N3-substitutions. The experimental results are supported by the computational studies. Photoinduced electron-transfer reaction of a series of mono and disubstituted 2,3- dihydroquinazolin-4(1H)-ones was investigated.