One-Pot Multicomponent Synthesis and Anticancer Activity of 1,3-Cyclopentathiazine and Pyrimidothiazine Derivatives

Novel 1,3-cyclopentathiazine and pyrimidothiazine derivatives were synthesized starting from 7-benzyl-4-phenylcyclopenta[ d ][1,3]thiazin-2-amine (CTA) prepared by a one-pot multicomponent reaction of cyclopentanone, benzaldehyde, and thiourea. Cyclocondensation of CTA with benzylidenemalononitrile gave a pyrimidothiazine. Oxidation of cyclopentathiazine with hydrogen peroxide afforded the corresponding epoxide, while its alkylation with ethyl iodide yielded an N -ethyl derivative. Cyclopentylidenemalononitrile was reacted with formaline and carbon disulfide to obtain pyridine-4-carbonitrile and thiapyrane, respectively, and the reactions of cyclopentylidenemalononitrile with aryl isocyanate and aryl isothiocyanate gave condensed diimino-substituted cyclopentanaphthyridine-1,6-dione and dithiaacenaphthylene-3,8-diylidedibenzamide, respectively. Heating cyclopentanone with benzoyl isothiocyanate and benzoyl chloride produced a sulfide derivative and an enolic dione, respectively. The structures of the newly synthesized compounds were confirmed by spectral analysis, and some products were screened for anticancer activity.