Simple Synthesis of 1,2-Dihydro-5,6-tri(tetra)methylenespiro(cyclopentane(cyclohexane)-2-thieno[2,3-d]pyrimidine-4(3H)-thiones)
A novel spiro-substituted heterocyclic system, 1,2-dihydro-5,6-tetramethylenespiro(cyclohexane-2thieno[2,3-d]pyrimidine-4(3H)-thione) (1) was obtained for the first time by condensation of cyclohexanone with cyanothioacetamide and sulfur [1]. We recently observed formation of this compound upon dimerization of cyclohexylidene cyanothioacetamide [2]. In this work, we show a third convenient route to potentially biologically active spiro-substituted nitrogen-containing heterocycles 1 [3], consisting of a one-pot synthesis for these compounds from N-(1-cycloalkenyl)morpholines 2 and cyanothioacetamide 3 in ethanol at 20°C. Upon alkylation of compound 1b by ethyl iodide in DMF, we obtained thioether 4. The structure of thione 1b, the mechanism for the formation of which is under study, was proven by X-ray diffraction (the detailed data will be published later).