2-Phenyl-4-bis(methylthio)methyleneoxazol-5-one: versatile template for diversity oriented synthesis of heterocycles

Abstract

4-Bis(methylthio)methylene-2-phenyloxazol-5-one (1) has been shown to be a versatile template for the synthesis of novel heterocyclic scaffolds. The key protocol involves nucleophilic ring opening of 1 with various primary aliphatic, aromatic amines and diamines to give open-chain amide adducts which are transformed into 4-bis(methylthio)methylene-2-phenyl-1-alkyl/arylimidazol-5-(4H)-ones (5) in good yields in the presence of anhydrous NaOAc/AcOH. Similarly, the amide adducts 4h–i from 3,4-dimethoxyphenylethylamine and tryptamine undergo interesting rearrangement in the presence of POCl₃ to furnish 1-(2-phenyl-5-methylthio-4-thiazolyl)dihydroisoquinoline and β-carboline derivatives 8–9 in good yields. The amide adduct 14 from o-phenylenediamine on exposure to refluxing acetic acid or in the presence of Ag₂CO₃ affords substituted 3H-1,5-benzodiazepinone, 2-(5-methylthio-2-phenyl-4-oxazolyl)-1H-benzimidazole and trisubstituted oxazole (15–17), whereas the bis-adduct from ethylenediamine yields ethylene bridge tethered bis-imidazole 23 and bis-oxazole 24 under similar reaction conditions. Probable mechanisms for the formation of various products have been suggested.