The Acid and/or Thermal Mediated Ring Contraction of 4H‐1,2,6‐Thiadiazines to Afford 1,2,5‐Thiadiazoles.

摘要: A near-quantitative acid and/or thermal mediated ring contraction of 3′, 5′-diarylspiro (benzo [d][1, 3] dioxole-2, 4′-[1, 2, 6] thiadiazines) affords 3-aryl-4-(2-arylbenzo [d][1, 3] dioxol-2-yl)-1, 2, 5-thiadiazoles. The reaction scope was studied providing 11 examples of this ring contraction. A double Wagner–Meerwein reaction mechanism is proposed.