Synthesis of Esterified/Fused Isocoumarins via Rh-Catalyzed C—H Activation/Transannulative Coupling/Annulation of Phthalic Anhydrides with Cyclic 2-Diazo-1,3-diketones and Methanol

Abstract

A rhodium(III)-catalyzed cascade reaction of phthalic anhydrides with cyclic 2-diazo-1,3-diketones and methanol for modular access to esterified cyclohexenone-fused isocoumarins has been developed. This strategy involves the process of one C-C and two C-O bonds formation through C-H activation, transannulative coupling and subsequent annulation process. Furthermore, no additive and base are needed in this transformation, and interestingly, the reaction could proceed well under air atmosphere with broad substrate and good functional groups tolerance.

Phthalic anhydride (PA): a valuable substrate in organic transformations

“…Surprisingly, the reaction proceeded well under air atmosphere with broad substrate and good functional group tolerance ( Scheme 93 ). 211 …”