Reactionsof 3-acetyl-4.4-bis( methy It hio) but-3-en -2-one 2e and methyl 2-acetyl-3,3-bis( methylth io)prop-2-enoate 2f with cyanothioacetamide, cyanoacetamide, or 2-amino-I ,3,3-tricyanoprop-I -ene and base, followed by treatment with acid, give polysubstituted pyridines such as 8,10,11,13,15 and 16. Further elaboration of these products leads to bicyclic systems such as thieno[2,3-6]pyridines 17 and 18 and pyrazolo[3,4-~]pyridine 21 and then to tricyclic systems including pyrazolo[3,4d]thieno[2,3-6]pyridine 19 and dipyrazolo[3,4-6: 3',4'-6]pyridine 22. ct-Oxoketene dithioacetals have proved useful starting materials for a variety of heterocyclic and homocyclic aromatic compounds. v 2 Ketene dithioacetals 2 derived from P-dicarbonyl and related compounds 1 (Scheme 1) should be equally N \ &O2Me I MeSAMeCN 5 CH2 \ Hii Mes)==(x MeS Y Y 1 2 a X = Y = C N d X=Y=C02Me b X = CN, Y = C02Me e X=Y=COMe c X = CN, Y = CONH2 f X = COMe, Y = C02Me g X=COMe,Y=H Scheme 1 Reugents: i, base; ii, CS,; iii, Me1 valuable, but have been much less studied. Recently, reactions of dithioacetals 2a, b with thioamides have been described. 3*4Reaction of these compounds with thioacetamide or thiobenzamide in the presence of sodium hydride, followed by treatment with acid, gave methylthiopyrimidines 4; the suggested mechanism is shown in Scheme 2. Methylation of the
