NaHCO3‐Promoted Formal [4+3] Annulation of Salicylaldehydes with Isoquinolinium Salts Accessing Isoquinoline‐Fused Benzo[f][1,3]oxazepines

Abstract A concise and practical sustainable strategy for modular access to isoquinoline‐fused benzo[ f ][1,3]oxazepine derivatives through a formal [4+3] annulation of commercially available salicyaldehydes with isoquinolinium salts has been developed. The reactions proceeded through the formation of two new bonds (C=C and C−O) and a seven‐membered heterocyclic ring in one pot. Remarkably, use of simple NaHCO 3 as a mild base, open atmosphere, nonhazardous reagents, nice functional group tolerance, and easily scale up are added characteristics to this approach. A wide range of substrates are compatible with this mild reaction system, thereby proving a facile and reliable protocol for constructing a benzo[ f ][1,3]oxazepine skeletons.