Dibenzo‐fused seven‐membered nitrogen heterocycles by a tandem reduction‐lactamization reaction

Abstract magnified image Efficient syntheses of dibenz[b,f][1,4]oxazepin‐11(10H)‐one, 5,10‐dihydro‐11H‐dibenzo[b,e][1,4]‐diazepin‐11‐one and 5,11‐dihydro‐6H‐dibenz[b,e]azepin‐6‐one are described using a tandem reductionlactamization sequence. Precursors for these ring systems are available in 1‐3 steps using nucleophilic aromatic substitution and Ullmann coupling methodology. Direct reduction‐lactamization of these compounds using iron powder in acetic acid at 115° affords the target heterocycles in ≥90% yield.