Radical Cyclization of N-Acylcyanamides to Pyrroloquinazolines

Significance

N-Acyl-N-cyanamides, readily prepared by two convenient methods, undergo radical-induced cyclization to afford polycyclic pyrro­loquinazolines in good to excellent yields. The proposed mechanism is a radical cascade reaction in which a 5-exo-dig cyclization process of the initial aryl radical leads to the cyanamide. The resulting radical is captured by an enone or an aromatic double bond to give the product. In the absence of unsaturated bonds, for example R¹, R² = Me, fragmentation occurs forming an ortho-cyano benzyl­amide.