One-pot synthesis of benzo[e]1,4-oxathiepin-5-ones under solvent-free condition via self-promoted thiolysis of 1,2-epoxides.

Under solvent-free conditions, thiosalicylic acid (2) efficiently self-promotes the thiolysis of 1,2-epoxides 1, anti-stereoselectively and generally totally beta-regioselectively. The resulting beta-hydroxysulfide products 3 have been obtained in very good yields. Benzo[e]1,4-oxathiepin-5-ones 4 have been easily prepared in a regio- and diasteroselective manner and in satisfactory yields under SFC by a one-pot protocol including nucleophilic ring opening of 1,2-epoxides 1 by thiosalicylic acid (2) and thermally induced lactonization of beta-hydroxy arylsulfides 3. Solvent-free condition and the absence of any catalyst make this procedure atom-economical and environmentally friendly.