Photocatalytic cyclization of 3-(2-isocyanophenyl)quinazolin-4(3 H )-ones for the construction of quinoxalino[2,1- b ]quinazolinones.

A new kind of building unit, 3-(2-isocyanophenyl)quinazolin-4(3 H )-ones, was designed and synthesized for the construction of novel quinoxalino[2,1- b ]quinazolinones. The radical cyclization of 3-(2-isocyanophenyl)quinazolin-4(3 H )-ones with ethers afforded ether-substituted tetracyclic quinoxalino[2,1- b ]quinazolinones under photocatalytic and metal-free conditions. In the process, the isocyano accepts a carbon radical to give an imidoyl radical, which adds to the electron-deficient CN bond in quinazolin-4(3 H )-one.