A [4+3] annulation of benzofuran-derived azadienes and α-bromohydroxamates for the synthesis of benzofuran-fused 1,4-diazepinones.

A Cs2CO3-mediated formal [4+3] cycloaddition involving benzofuran-derived azadienes (BDAs) and α-bromohydroxamates to afford benzofuran-fused 1,4-diazepinones is established. This is the first example of using BDAs for the construction of seven-membered dinitrogen-fused heterocycles. This strategy not only enriches the chemistry of BDAs but also provides an interesting class of bioisosteres of 1,4-benzodiazepine.