Some Reactions of 3-Hydroxy-1-phenylpyrazole

Synthesis of 3-substituted 1-phenyl-1H-pyrazole-4-carbaldehydes and the corresponding ethanones by Pd-catalysed cross-coupling reactions

“…A solution of 4-bromo-3-hydroxy-1-phenyl-1H-pyrazole 2 18 (1.67 g, 7 mmol) in dry DMF (20 mL) was cooled to 0 ºC under inert atmosphere and NaH (60% dispersion in mineral oil, 280 mg, 7 mmol) was added portion wise. After mixing for 15 min.…”

“…To this purpose, 1 was brominated according to a known procedure. 18 The ; ii: BnCl, NaH, DMF, 0-60 °C, 1 h, 73% for 3, 85% for 5; iii: n-BuLi, THF, DMF, -78 °C, rt, 0.5 h, 70%; iv: POCl 3 , DMF, 70 °C, overnight, 60%; v: TFA, rt, 2 days, 85%; vi: Tf 2 O, TEA, DCM, rt, 1 h, 83%.…”

Ring-closing metathesis as a key step to construct 2,6-dihydropyrano[2,3-c]pyrazole ring system

“…[27][28][29][30] The O-allylation of 1a with allyl bromide in the presence of NaH gave O-allylated pyrazole 2a. 31 To introduce a formyl group at the 4-position of the pyrazole ring, we employed a previously reported procedure based on the Vilsmeier-Haack reaction. 32 Heating compound 2a with POCl3 in N,N-dimethylformamide (DMF) at 60 °C resulted in the formation of the desired pyrazole-4-carbaldehyde 3a in 91% yield (Scheme 1).…”

4-Bromo-3-methoxy-1-phenyl-1H-pyrazole

“…The preparation of 2 was carried out according to a standard method for O-alkylation, namely by reaction of 4-bromo-1-phenyl-1H-pyrazol-3-ol (1) [9] with methyl iodide in alkaline medium, which afforded the title compound in 88% yield after column chromatograpy (Scheme 1).…”

“…The preparation of 2 was carried out according to a standard method for O-alkylation, namely by reaction of 4-bromo-1-phenyl-1H-pyrazol-3-ol (1) [9] with methyl iodide in alkaline medium, which afforded the title compound in 88% yield after column chromatograpy (Scheme 1). Although compound 2 is reported in a patent application, neither an experimental procedure for its preparation nor spectroscopic/physical data, was provided [10].…”