Thieno pyrazoles synthesis

Thieno[3,4-d]oxazole-3a(4H)-carboxylic acid, dihydro-2-methyl-synthesis, 6, 1020 Thieno[2,3-d Joxazoles synthesis, 6, 990 Thieno[3,2-g]pteridine structure, 3, 284 lH-Thieno[3,4-c]pyran-2-ones synthesis, 4, 1032 Thienopyrazines synthesis, 4, 1022-1024 Thieno[2,3-6]pyrazines, 4, 1023 electrophilic substitution, 4, 1024 Thieno[3,4-6]pyrazines, 4, 1024 Thieno[3,4-c]pyrazole, 4,6-dihydro-3-hydroxy-carbamates... 

Another nonclassical heterocycle, thieno[3,4-cJpyrazole, was synthesized,109 utilizing the ability of mesoionic ring systems to act as 1,3 dipoles in cycloadditions.106 Condensation of JV-phenylsydnone (162) with dibenzoylacetylene formed 3,4-dibenzoyl-l-phenylpyrazole (163) (85%) with phosphorus pentasulfide in refluxing pyridine, this gave 85% of 2,4,6-triphenylthieno[3,4-c]pyrazole (164) [Eq. (44)]. The synthesis of 5-methyl-1,3,4,6-tetraphenylthieno[3,4-c]pyrrole is also described.107... 

In variants of the above processes, the bifunctional reactivity of 4-(dialkylamino-methylene)pyrazolin-5-thiones (155) (Scheme 25) and oxazolin-5-thiones (157) (Equation (45)) with a-halocarboxylic acids (or esters) was exploited for the synthesis of thieno[2,3-c]pyrazoles (156)... 

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