Transition metal-free one-pot synthesis of fused 1,4-thiazepin-5(4H)-ones and theoretical study of the S-N type smiles rearrangement process.

A series of 1,4-thiazepin-5(4H)-one derivatives were synthesized via a transition metal-free one-pot Smiles rearrangement process at room temperature. Regioselective seven-membered heterocycles were constructed in good to excellent yields. To gain an in-depth understanding of the S-N type Smiles rearrangement mechanism, a theoretical study was also performed by quantum chemistry calculations.