4-Fluorophenylhydrazine hydrochloride synthesis
- Product Name:4-Fluorophenylhydrazine hydrochloride
- CAS Number:823-85-8
- Molecular formula:C6H8ClFN2
- Molecular Weight:162.59
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823-85-8
The general procedure for the synthesis of 4-fluorophenylhydrazine hydrochloride from 4-fluoroaniline was as follows: 4-fluoroaniline (127.6 g, 1 mol) was dissolved in concentrated hydrochloric acid (293 mL) and stirred for 2 hours at room temperature. Subsequently, the above solution was slowly added dropwise to a solution of sodium nitrite (72.5 g, 1.05 mol) in water (145 mL) at a temperature controlled below 5 °C. After the dropwise addition, stirring was continued for 1 hour, and then the filtrate was separated by filtration to obtain the filtrate. A solution of NaHSO3 (213.2 g, 2.05 mol) in water (500 mL) was slowly added dropwise to the filtrate over a temperature range of 0-10 °C while the pH was adjusted with 25% NaOH solution to maintain between 6-7. The reaction mixture was heated to 80 °C and maintained at this temperature for 1 hour. Upon completion of the reaction, the mixture was cooled to room temperature and then concentrated hydrochloric acid (600 mL) was added dropwise. Next, the mixture was heated to 90-100°C for 1 hour. Finally, the mixture was cooled to 10 °C and the precipitate was collected by filtration to give the light red solid product 4-fluorophenylhydrazine hydrochloride (129.3 g, 60% yield).
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Yield:823-85-8 75%
Reaction Conditions:
Stage #1:1-Bromo-4-fluorobenzene with potassium phosphate;N,N'-bis(2,5-dimethylpyrrol-1-yl)oxalamide;cetyltrimethylammonim bromide;copper(I) bromide in water at 110; for 0.166667 h;Sealed tube;Inert atmosphere;
Stage #2: with hydrazine hydrate in water at 110; for 1 h;Sealed tube;Inert atmosphere;
Stage #3: with hydrogenchloride in dichloromethane;water
Steps:
4.6. General procedure for C-N coupling reaction of arylbromides and hydrazine hydrate on a 10 mmol scale
General procedure: CuBr (36 mg, 0.25 mmol, 2.5 mol %), L3 (110 mg, 0.4 mmol,4 mol %), H2O (0.5 mL), and K3PO4 (254 mg, 1.2 mmol) were mixedin a 15 mL screw cap test tube. After STAC (110 mg, 0.3 mmol,3 mol %) and aryl bromide (10 mmol) were added, the resulting mixture was stirred at 80-110° C (bath temperature) for 10 min.Then K3PO4 (2.29 g, 10.8 mmol) and N2H4*H2O (1 g, 20 mmol) were added and argon (flow rate 5-7 mL/min) was bubbled through thereaction mixture for 5 min.28 The reaction mixture was stirred ina closed test tube at 80-110° C (bath temperature) for 1-2 h until complete consumption of starting material was observed as monitoredby TLC (eluentehexane), then cooled to room temperatureand diluted with SH2Cl2 (50 mL). The resulting solutionwas filteredand washed with brine (225 mL). Aq HCl (37%) was added to the CH2Cl2 solution dropwise until pH 3-4. The formed precipitate was filtered, washed with SH2Cl2 (15 mL) and dried atroom temperature. NMR spectra of certain synthesized aryl hydrazine hydrochlorides showed that they contained 1-5 mol % of the corresponding aniline hydrochlorides as impurities (see Supplementary data). Analytical samples of aryl hydrazine hydrochlorides were purified via precipitation from methanol solution by adding 2-3 volumes of diethyl ether.
References:
Kurandina, Daria V.;Eliseenkov, Eugene V.;Ilyin, Petr V.;Boyarskiy, Vadim P. [Tetrahedron,2014,vol. 70,# 26,p. 4043 - 4048]
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