Thermal rearrangement of 1, 4-dithiocyanatobut-2-enes, available by either thiocyanogenation of 1, 3-dienes or from 1, 4-dihalogenobut-2-enes, affords vicinal thiocanatoisothiocyanates, which are trapped to give thiazolidinones or dihydrothiazoles, or indirectly aminothiols.