NH4OAc‐Promoted Cascade Approach towards Aberrant Synthesis of Chromene‐Fused Quinolinones

Abstract

A concise cascade strategy for the synthesis of 6H‐chromeno[4,3‐b]quinolin‐6‐ones was developed from 4‐hydroxycoumarins and arylhydrazine hydrochlorides in DMSO. The synthetic strategy relies on dual role of ammonium acetate in generating 4‐aminophenyl coumarin from arylhydrazine via aryl radical formation, and Csp2‐H formylation of coumarin using DMSO as a methine source. The strategy is scalable, and an array of arylhydrazine hydrochlorides delivered chromene‐fused quinolinones in good to excellent yields.