39513-09-2

Upstream product

• 87389-78-4 2-amino-4-methyl-5-phenyl-1,2-dihydro-pyrazol-3-one 
• 74-88-4 methyl iodide 
• 29707-10-6 1,1-dimethyl-3-phenylpyrazolium-5-oxide 
• 610289-29-7 1,1-dimethylamino-5-phenylpyrrole-2,3-dione 
• 13466-32-5 acetophenone dimethylhydrazone 

Relevant academic research and scientific papers

Catch-and-release of HNO with pyrazolones

A new and versatile class of HNO donors, the (hydroxylamino)pyrazolone (HAPY) series of HNO donors utilizing pyrazolone (PY) leaving groups, is described. HNO, the smallest N-based aldehyde equivalent, is used as a reagent along with a variety of PY compounds to synthesize the desired HAPY donors in what can be considered an N-selective HNO-aldol reaction in up to quantitative yields. The bimolecular rate constant of HNO with PY in pH 7.4 phosphate buffer at 37 °C can reach 8 × 105 M-1 s-1. In 1H NMR experiments, the HAPY compounds generate HNO quantitatively (trapped as a phosphine aza-ylide) with half-lives spanning 3 orders of magnitude (minutes to days) under physiologically relevant conditions. B3LYP/6-31G calculations confirm the energetically favorable reactions between HNO and the PY enol and enolate, whereas HNO release is expected to occur through the oxyanion (OHN-PY) of each HAPY compound. HNO has been shown to provide functional support to failing hearts.

N-Aminopyrroledione-hydrazonoketene-pyrazolium oxide-pyrazolone rearrangements and pyrazolone tautomerism

Flash vacuum thermolysis (FVT) of 1-(dimethylamino)pyrrole-2,3-diones 5 causes extrusion of CO with formation of transient hydrazonoketenes 7. The transient ketenes 7 are observable in the form of weak bands at 2130 (7a) or 2115 cm-1 (7b) in the Ar matrix IR spectra resulting from either FVT or photolysis of either 5 or 1,1-dimethylpyrazolium-5-oxides 8, and these absorptions are in excellent agreement with B3LYP/6-31G* frequency calculations. Under FVT conditions the ketenes 7 cyclize to pyrazolium oxides 8, which undergo 1,4-migration of a methyl group to yield 1,4-dimethyl-3-phenylpyrazole-5(4H)-one 9a and 1,4,4-trimethyl-3-phenylpyrazole-5(4H)-one 9b. All three tautomers of 9a have been characterized, viz. the CH form 9a (most stable form in the gas phase, the solid state and solvents of low polarity), the OH form 9a′ (metastable solid at room temperature) and the NH form 9a″ (stable in aprotic dipolar solvents). The isomeric 1,4-dimethyl-5-phenylpyrazole-3(2H)-one 12 tautomerizes to the 3-hydroxypyrazole 12′. The crystal structure of the hydrochloride 14 of 9a′/9a″ is reported, representing the first structurally characterised example of a protonated 5-hydroxypyrazole.

1-Aminopyrazolin-5-ones. Synthesis and reactivity

A synthesis of 1-aminopyrazolin-5-ones (I) by chloramine attack on the 2-benzylpyrazolones (IV d-e) has been accomplished.Nucleophilic substitution reactions of aminopyrazolones (I) are investigated; with 1,4-diketones, N,N'-pyrrolylpyrazolones (XVIIa-c)