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 C- and N-substitutions on the retention or elimination of the C-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 N- and N-atoms can be involved in this process. The extent of the N- and N-atoms contributions in this electron-transfer process and also the retention or elimination of the C-substitutions are dependent on the nature and steric hindrance of both C- and N-substitutions.