A Rh(iii)-catalyzed cascade C–H functionalization/cyclization reaction of salicylaldehydes with diazomalonates for the synthesis of 4-hydroxycoumarin derivatives.

A cascade C–H functionalization/cyclization reaction of salicylaldehydes with α-diazomalonates has been developed for the synthesis of 4-hydroxycoumarin derivatives under the catalysis of rhodium(iii) and in the presence of acetic acid. A plausible mechanism involving aldehydic C(sp2)–H activation by rhodium(iii) and rhodium(iii) catalyzed carbene insertion is also proposed. [ABSTRACT FROM AUTHOR]