Ring Enlargement Reaction of <i>C,N</i>-Cyclic‑<i>N</i>′‑acyl Azomethine Imines with Sulfonium Ylide: An Efficient Synthesis of 3‑Benzazepine Derivatives

Highly efficient formation of 3-benzazepine derivatives has been achieved, based on the ring expansion reaction of C,N-cyclic-N′-acyl azomethine imines with sulfonium ylide generated in situ from the corresponding sulfonium salt. The reactions proceeded smoothly to afford the tricyclic 3-benzazepine derivatives in good to high yields. A wide range of C,N-cyclic N′-acyl azomethine imines were applicable to this reaction.