Zinc-Catalyzed Synthesis of Pyrazolines and Pyrazoles via Hydrohydrazination

Abstract

A novel regioselective synthesis of aryl-substituted pyrazolines and pyrazoles has been developed. Substituted phenylhydrazines react with 3-butynol in the presence of a catalytic amount of zinc triflate to give pyrazoline derivatives. The resulting products are easily oxidized in a one-pot procedure to the corresponding pyrazoles.

3‐Rhoda‐1,2‐diazacyclopentanes: A Series of Novel Metallacycle Complexes Derived From CN Functionalization of Ethylene

“…In the present case, a similar decrease in 3 J H,H was observed for the N-containing analogues: 7.8 Hz for [8] + , 6.8 and 6.6 Hz for [7] + and [16] + , and 5.6 Hz for [9] + [14] ( Table 1). These coupling constants are all consistent with the formation of mononuclear four-, five-, and six-membered ring systems.…”

“…A singlet of integration two was also observed at 5.38 ppm for the axial methylene TPA methylpyridyl arm. Carbamate hydrolysis was also attempted through treatment of [7] + with methanolic KOH at room temperature, followed by oxidation employing CuCl 2 . [22] While hydrolysis of [7] + could be facilitated, subsequent oxidation failed due to sensitivity of the "free-hydrazine" complex to base.…”

“…We show this methodology to be tolerant of electron-deficient azo compounds including azo diesters (RCO 2 N=NCO 2 R; R = Et [3]Cl, R = iPr [4]Cl, R = tBu [5]Cl, and R = Bn [6]Cl) and a cyclic azo diamide: 4-phenyl-1,2,4-triazole-3,5-dione (PTAD), [7]Cl. The latter complex features two ortho-fused ring systems and constitutes the first 3-rhoda-1, 2-diazabicyclo[3.3.0]octane.…”

Pt–Sn/γ‐Al2O3‐Catalyzed Highly Efficient Direct Synthesis of Secondary and Tertiary Amines and Imines

“…Benzylamine (2 s) reacted with 1 a to give dibenzylamine (3 as) in 95 % yield, whereas cyclohexylamine (2 t), 2-(aminomethyl)pyridine (2 u), and benzhydrylamine (2 v) exhibited relatively low reactivity (Table 2, entries [20][21][22], which revealed unfavorable electronic and steric effects from the amine substrates. However, the reactions of aliphatic secondary amines 2 w-y and 3 as gave the corresponding tertiary amines in good to excellent yields (83-97 %, Table 2, entries 23-26).…”

Benzyloxyphenyl based synthesis of some novel N-acetylpyrazolines

“…Pyrazoline is also synthesized by using microwave irradiation [10], tungsten light irradiation [11], and ultrasound irradiation [12]. Recently, various modified methods have been reported for synthesis of 2-pyrazolines by using different catalysts such as KHSO 4 [13][14][15][16][17][18][19]. Greener and environmentally benign syntheses of 2-pyrazolines using solvent-free grindstone technique were reported [20].…”