Photomediated Tandem Sulfonyl Addition-Chemoselective N-Cyclization of o- Alkenyl Aryl Ureas: Direct Assembly of Functionalized Dihydroquinazolinones

Photoredox mediated tandem addition-chemoselective cyclization of o-alkenyl aryl ureas are reported for the synthesis of sulfonyl and other electrophilic radical decorated dihydroquinazolinones. By a careful choice of o-alkenyl aryl urea starting materials, we have achieved chemoselective N-cyclization in the presence of a more reactive amidic oxygen. We have demonstrated the scope of the methodology with a variety of o-alkenyl aryl ureas and sulfonyl chlorides including simple aliphatic sulfonyl chlorides, which are less commonly explored. Finally, we also demonstrated the application of our methodology with other electrophilic radicals, which afforded the resultant products in good yields under slightly modified conditions. Quenching studies with TEMPO, revealed a radical mechanism and finally, large-scale synthesis of sulfonyl substituted dihydroquinazolinone showcases the synthetic utility of the methodology.