27/-Thieno pyrazoles

A similar treatment of the Schiff s base derived from 3-nitro-2-thienylcarbaldehyde (564) with triethyl phosphite gave the thieno[3,2-h]pyrazole (565) (78CC453). ... 

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... 

Thermolysis of the l-(2-thienyl)-3-diazoalkenes 1 gives 3//-thieno[3,2-f]-l,2-diazepines 2 by sequential 1,7-dipolar electrocyclization and [l,5]-hydrogen shifts, together with 37/-pyrazoles 3, which are produced by a competing 1,5-cyclization.140... 

Heating the l-(3-thienyl)-3-diazoalkenes 5 gives 3//-thieno[2,3-f]-l,2-diazepines 4. In the case of 5b, the pyrazole 6b is also formed.140... 

The 5-position was the most reactive in bromination of 1,3-disubstituted l//-thieno- and -seleno-[3,2-c/]pyrazoles (59), whereas the isomeric 2H-[3,2-c] derivatives (60) reacted at the 6-position [73JOU2216 77CS( 12)1 ]. 

The cycloaddition of nitrilimines toward furo[3,4-c]thieno[2,3-r7]-pyrazoles has been investigated as a function of the electron-withdrawing or electron-donating character of the substituents attached to the aromatic rings <2000H(53)917>. For instance, nitrilimine 459, obtained in situ from hydrazonoyl chloride 458, by base treatment with silver carbonate in dioxane, when reacted with 460, gives a mixture of compounds 461 and 63 (Scheme 53) <2000H(53)917>. 

An essentially similar approach has been used for the synthesizing thieno[2,3-c]pyrazoles. Thus, 307 reacted with a-chloroacids (R = H, Me) to give the corresponding thieno[2,3-c]pyrazoles (309), via 308 (71ZOR1253). 

Similarly l-phenyl-3-methyl-4-formyl-5-chloropyrazole reacts with thioglycollic acid in the presence of alkali to yield a mercaptopyrazole derivative that could be cyclized to thieno[2,3-c]pyrazole in the presence of alkali (69KGS760, 69ZOR1498). Similar to this is the reported formation, via 311, of 312 from 310 and mercaptoacetanilide (73ZOR2416). 

Conversion of ethyl 5-chloropyrazole-4-carboxylate into 4-hydroxy-thieno[2,3-c] pyrazoles, via ethyl 5-(phenylcarbomoylmethylthio)-4-pyrazole carboxylate intermediates, has also been reported (72USP3649641). The reaction of disulfide 313 with nitromethane gives 314 (74TL4069). 

Reaction of the quaternized salts of 4-ethoxycarbonyl-3,5-dimethyl-f-phenylpyttolo(furo or thieno)[2,3-c]pyrazole 34 with the iodomethane quaternary salts of pyridine, quinoline, and isoquinoline in ethanol with catalytic piperidine gave 3-[4(f)]-monomethine cyanine dyes (e.g., 35). Additionally, 3-[2(4)]-trimethine cyanine dyes and 4-[2(4)]-di-3[2(4)]-tri-mixed methine cyanine dyes (e.g., 36 and 37, respectively) were similarly prepared from the intermediates derived by reaction of 34 with triethyl orthoformate in the presence of piperidine (Scheme 8) <2002CCS106f>. 

These methods are limited in scope. Direct thiation has been reported for the transformation of vicinal diketones to [3,4]-annelated thiophenes <1996CHEC-II(7)49>. Thionations and selenations of vicinal halomethyl ketones with thioacetamide or iV,iV-diethylselenopropionamide as sulfur and selenium donors, respectively, have also been reported <1996CHEC-II(7)49>. In a recent example, thieno[3,4-f]pyrazoles 160 were readily prepared from aryl 5-bromomethyl-l//-l-phenylpyrazole-4-yl ketones 159 by reaction with thioacetamide (Equation 35) <1998JHC71>. Additionally, an example of an amination cyclization by reaction of 161 with benzylamine to afford pyrrolo[3,4-i/ thiazole 162 has been described (Equation 36) <1998JHC71>. 

---