A new general synthesis of 3- and 3,4-substituted 4a–q, 3,4-annelated 7a–d and condensed tricyclic 9a–e thiophenes has been developed through Simmons-Smith reaction on the respective α-oxoketene dithioacetals. Extension of the reaction to α-cinnamoylketene dithioacetals 10a–e and its higher enyl analogs 13a–d, 15a–c gave the corresponding 3-styryl 11a–e and 3-di- and trienyl 14a–d, 16a–c thiophenes
Cyclocondensation of oxoketene dithioacetals with 3-aminopyrazoles: a facile highly regioselective general route to substituted and fused pyrazolo ]pyrimidines
3-amino-5-methylthio-4-phenylpyrazole (1b) withα-oxoketene dithioacetals (2a-j derived from acyclic active methylene ketones affords 5-methylthio-6,7-substituted pyrazolo[1,5-a]pyrimidines (3a-J) exclusively. The reaction was found to be equally successful for the synthesis of 7-styryl,7-(4-aryl-1,3-butadienyl) and 7-(6-aryl-1,3,5-hexatrienyl)pyrazolopyrimidines (7a-f) from the respective enoylketene dithioacetals (6a-f)