The behaviour of E,Z-5-arylmethylidene-2-thioxo-1,3-thiazolidin-4-one and 3-[(2-oxo-2H-1-benzopyran-3-yl) dithio]-2H-1-benzopyran-2-one derivatives towards some amines

The reaction of 2-thioxo-1,3-thiazolidin-4-one with salicylaldehyde or its 5-bromo derivative in acetic acid and sodium acetate gave a mixture of E,Z- or E-5-arylmethylidene-2-thioxo-1,3-thiazolidin-4-ones (IIIa or IIIb) and the disulfide derivatives IV and IVb, respectively. Treatment of IIIa with benzylamine or morpholine in dioxane at room temperature afforded 3-benzylamino-2H-1-benzopyran-2-one (VIa) or E,Z-2-thiazolin-4-one derivative together with the amine salt, respectively. Similar treatment of IIIb with benzylamine yielded the E,Z-2-thiazolin-4-one derivative and the disulfide IVb as the major product. The disulfide IVa reacted with benzylamine in cold dioxane to yield the disulfide derivative of 4-benzylamino-2H-benzopyran-2-one in addition to VIa, whereas in boiling dioxane it gave VIa and the corresponding bisbenzyl derivative. On the other hand, when IIIb or IVa was treated with dicyclohexylamine in dioxane, it gave IVb as well as the amine salt in the former case and 3-sulfanyl-2H-1-benzopyran-2-one in the latter one. Structures of all products were evidenced by elemental analysis and spectral data.