New one-pot, efficient, and regioselective method for the synthesis of 3-Trifluoromethyl-1H-1-phenylpyrazoles and alkyl 3-carboxylate analogs

New 4-fluoroalkyl substituted N-phenylpyrazoles: Synthesis promoted by DAST and multinuclear NMR analysis

“…Therefore, we first carried out formylation reactions on 3-and 5-trifluoromethyl-1H-1-phenylpyrazoles [24,25] employing two different Vilsmeyer-Haack reagents: (i) POCl 3 in DMF [26,27] or (ii) oxalyl chloride in…”

Friedel-Crafts chemistry: Part 41. A new facile synthesis of indeno[1,2-c] pyrazoles, 2H-benzo[g]indazoles and benzo[6,7]cyclohepta[1,2-c]pyrazoles via Friedel-Crafts ring closures

“…The assignment of the diastereotopic protons of the methylene group directly bonded to pyrazole or pyrazolone rings (2a,c and 3b,d) beside their intermediates alcohols and acids (12a, 16b and 10a, 14b) were made on the basis of J-values that were obtained by direct inspection of the 1 H NMR spectrum which in turn showed a greatly change in chemical shifts. It is known that the extent of shielding is proportional to the electronegativity exerted by the heterocyclic ring or the neighbored functional groups and its proximity to the hydrogen [63][64][65][66].…”

Easy and regioselective access to dimethyl acetal-protected heterocycles and their efficient allylation reactions mediated by allylaluminum reagent

“…This observation was previously described in another work of our research group. 41 The pyrimidine 5 presents, among other signals, the 1 H NMR chemical shifts of the H-5 as a characteristic singlet at δ 7.6 ppm. The 1 H NMR signals for the 2,2-dimethoxyethyl substituent are characterized by the presence of one triplet near δ 4.5-4.9 ppm with a coupling constant of 6 Hz for the methine proton, and a doublet near δ 2.6-3.7 ppm for the methylene protons.…”