Acetic Acid → (4-Cyclopropyl-3,4-dihydro-2H-quinoxalin-1-yl)-[4-(2,5-dichloro-4-hydroxy-phenoxy)-pyridin-3-yl]-methanone

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

To a solution of 1.0 g (1.93 mmol) [4-(4-bromo-2,5-dichloro-phenoxy)-pyridin-3-yl]-(4-cyclopropyl-3,4-dihydro-2H-quinoxalin-1-yl)-methanone (Example 26) in 20 mL dry tetrahydrofuran was added 0.85 mL (3.72 mmol) triisopropylborate (commercially available, CAS RN 5419-55-6). The solution was cooled to −75° C. using a dry ice bath and 1.50 mL (2.4 mmol) n-butyllithium solution (1.6M in n-hexane) was added over 3 min. to the reaction mixture. Stirring was continued for another 1.5 hours. The dry-ice bath was replaced by an ice bath and 0.98 g (8.17 mmol) acetic acid (50% solution in water) and 0.28 g (2.89 mmol) hydrogen peroxide (35% solution in water) were added. The reaction mixture was stirred at 0° C. for 1 hour, the cooling batch was removed and stirring was continued at room temperature for 20 hours. The solution was poured on 10% aqueous sodium thiosulfate solution and extracted three times with ethyl acetate. The combined organic layers were washed with brine, dried over magnesium sulfate, filtered, treated with silica gel and evaporated to dryness. The resulting powder was purified by silica gel chromatography using a MPLC system (20 g silica gel column, CombiFlash Companion, Isco Inc.) with a gradient of n-heptane:ethyl acetate (100:0 to 40:60) to give 0.575 g (65%) of the title compound as a light brown solid. MS (ESI): m/z=456.2 [M+H]+.

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