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With caesium carbonate In N,N-dimethyl-formamide at 180℃; for 1.5 h; Microwave irradiation
Step 1 : 4-Bromo- 1 -cyc A mixture of 4-bromo-lH-pyrrazole (1.0 g, 6.8 mmol), bromo cyclopropane (1.3 g, 10.7 mmol), cesium carbonate (3.5 g. 10.7 mmol), and DMF (6 mL) in a 30 mL microwave vial is heated to 180 °C under radiation for 1.5 hr. After cooled to room temperature, the reaction mixture is filtered. The filtrate is concentrated and the residue is purified on a silica gel flash chromatography with ethyl acetate/petroleum ether (1 :5) to get a brown liquid (0.87 g, 68percent yield). (MS: [M+l] 259)
With sodium acetate;dichloro(1,1'-bis(diphenylphosphanyl)ferrocene)palladium(II)*CH2Cl2; In N,N-dimethyl-formamide; at 150℃; for 1h;Inert atmosphere; Sealed microwave vial;
Bis(pinacolato)diboron (330 mg, 1.3 mmol), NaOAc (262 mg, 3.2 mmol), and Pd(dppf)Cl2-dichloromethane complex (89 mg, O. l lmmol) were combined in a microwave vial. 4-Bromo-l -cyclopropyl- lH-pyrazole and DMF (4 mL) were added and the vial was flushed with argon and sealed. The reaction mixture was heated in a microwave for 60 min at 150 0C. The reaction was diluted with 10 mL water and extracted 3 x 10 mL with EtOAc. The combined organic layers were dried over Na2Spsi4 and concentrated to yield 120 mg of the title compound as a dark oil, m/z 235.4 [M +H]+.
Step 1 : l-Cyclopropyl-4-(4,4,5,5-tetramethyl-l,3,2-dioxaborolan-2-yl)-lH-pyridaziiie To a 100 n L flask is added 4-bromo-l-cyclopropylpyrazol (6.57 g, 35.1 mmol) and anhydrous THF (30 niL). The solution is cooled to -78 °C under nitrogen; then n-butyl lithium (15.5 n L, 2.5 M in hexanes, 38.6 mmol) is added dropwise. The reaction mixture is stirred at the temperature for 1 hr, followed by addition of isopropyl boronate (9.17 g, 94.1 mmol) and stirred below -70 °C for 3 hours. The reaction is quenched with water (20 n L) and the resulted mixture is adjusted to pH 8-9 with aqueous hydrochloride solution (1 N). The combined organic phases are concentrated and used in next step without further purification (6.64 g, 81percent yield). (MS: [M+l] 235)
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