Synthesis and Alkylation of Pyrano[4′′,3′′:4′,5′]pyrido[3′,2′:4,5]thieno[3,2-d]pyrimidine-8,10-dithione

Effective methods were proposed for the synthesis of 1-amino-8,8-dimethyl-5-piperidin-1-yl-8,9-dihydro-6H-pyrano[4,3-d]thieno[2,3-b]pyridin-2-carbonitrile and pyrano[4′′,3′′:4′,5′]pyrido[3′,2′:4,5]thieno[3,2-d]pyrimidine-8,10-dithione. A new intramolecular cyclization was discovered: the transformation of the thiazine ring into a pyrimidine ring. A plausible reaction mechanism was proposed, involving the formation of the corresponding thiazine ring followed by recyclization to the target compound. An effective method was developed for preparing bis-thioalkyl derivatives of thieno[3,2-d]pyrimidine with high yields.