Improved Synthesis of 1H-Pyrazole-4-carbaldehyde

Unconventional Method for Synthesis of 3-Carboxyethyl-4-formyl(hydroxy)-5-aryl-N-arylpyrazoles

“…Due to the synthetic versatility of the 4-formyl- N -arylpyrazole skeleton, their synthesis has been extensively explored. Over time, numerous synthetic strategies have been employed for the preparation of these intermediates, − in particular the Vilsmeier–Haack reaction, which is based on the 4-position formylation of N -arylpyrazole by DMF/POCl 3 (Vilsmeier–Haack reagent) (Scheme , ROUTE A). Another approach is the reaction of N -aryl hydrazones of methyl ketones or aldehydes with Vilsmeier–Haack reagent (Scheme , ROUTE B). , …”

N-Methylimidazole Promotes the Reaction of Homophthalic Anhydride with Imines

“…The reaction mixture was stirred at −30 °C for 2.5 h and then at 23 °C for 24 h, concentrated, and then (E)-N-((1H-Pyrazol-4-yl)methylene)-2,2,2-trifluoroethanamine. Solid 4-pyrazolecarboxaldehyde hydrochloride (10.0 g, 76 mmol), prepared by the literature method, 16 was added to a cooled (ice bath) solution of 2,2,2-trifluoroethylamine hydrochloride (15.2 g, 113 mmol) in 36 mL of acetonitrile, followed by triethylamine (31.5 mL, 226 mmol). The resulting reaction mixture was allowed to warm to 23 °C and was stirred for an additional 15 h. The reaction mixture was filtered, and the solids were washed with 50 mL of acetonitrile.…”

Synthesis of substituted-3-iodo-1H-pyrazole derivatives and their further modification under Sonogashira cross coupling reaction conditions

“…17 1-(1-Ethoxyethyl)-1H-pyrazole-4-carbaldehyde (16) was synthesized in good yield using this intermediate. Thus, we wanted to compare the reactivity of 1-(1-ethoxyethyl)-3-iodo-1H-pyrazole (2a), 4-iodopyrazole 3a and 3,4-diiodopyrazole 6a towards alkyl magnesium halides and to evaluate the possibilities of application of Grignard reagents in derivatization of iodopyrazoles to pyrazole aldehydes.…”

“…[17][18][19] Tetrahydropyran (THP) group is recommended for the synthesis of unsymmetrical pyrazole derivatives. 20 Usually protection reaction of pyrazole ring with EtOEt or THP groups are performed by heating reaction mixture of starting pyrazoles with ethyl vinyl ether or dihydropyran and catalytic amount acid 40-50 °C.…”