NaOAc-Promoted [3+1+2] Annulation of O‑Pivaloyl Oximes, Aldehydes, and 2‑Methylbenzothiazole Salts: Synthesis of 1‑Azaphenothiazines

This paper presents an efficient strategy for constructing 1-azaphenothiazines through the NaOAc-promoted [3+1+2] annulation of O-pivaloyl oximes, aldehydes, and 2-methylbenzothiazole salts. The reaction is conducted in ethanol and employs oxygen as the oxidant under catalyst-free conditions. The process is amenable to various O-pivaloyl oximes, 2-methylbenzothiazole salts, and aldehydes, affording the target products in satisfactory yields.