Condensed sulfur-containing pyridine systems 3.* Construction of penta- and hexacyclic heterocyclic systems by the cascade reaction of 3-cyanopyridine-2(1H)-thiones and 3-cyano-pyridine-2(1H)-thiolates with 8-chloromethyl-3-methyl-7-(2-oxo-2-phenylethyl)xanthene

The alkylation of 3-cyanopyridine-2(1H)-thiones with 8-chloromethyl-3-methyl-7-(2-oxo-2-phenylethyl)- xanthene in a KOH–H2O–DMF system upon heating leads to the formation of pyrido-[3",2":4',5']thieno[3',2':5,6][1,4]diazepino[7,1-f]purine-2,4(3H,6H)-dione derivatives in good yields. Under milder conditions, the intermediates of the cascade reactions, namely, 2-({[3-methyl-2,6-dioxo-7-(2-oxo-2-phenylethyl)-2,3,6,7-tetrahydro-1H-purin-8-yl]methyl}thio)pyridine-3-carbonitriles, can be isolated and characterized.