Aryl diazonium salts are an important class of organic compounds that are now widely used as arylating agents in photoredox catalysis owing to their lower redox potential, broad substrate scope, and atom economy. They have successfully been used in many interesting organic transformations to introduce an aryl group. They serve as good alternatives for aryl halides and other aryl organometallic reagents primarily used as aryl group surrogates. New reactions using aryl diazonium salts are continually emerging, and in this review, we have highlighted some recent developments in photoredox arylations and their applications. 4.3. Oxy-Arylation of Alkynes for the Synthesis of Benzofuran 4.4.

A highly chemoselective C–H arylation of phenylureas of the type ArNHCONH2 was achieved using dual catalysis.

Herein, we report a substrate-controlled cascade cyclization of o-alkenyl aryl ureas, an ambident nucleophile for constructing functionalized heterocycles such as 2-amino-1,3-benzoxazines and dihydroquinazolinones in a chemodivergent fashion using photoredox catalysis...

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.