Citric Acid → (E)-8-(4-Methyl-2-propylbenzimidazol-1-yl)methyl-11-(5-oxo-4,5-dihydro-1,2,4-oxadiazol-3-yl)methylene-6,11-dihydrodibenzo[b,e]oxepine

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Reaction Steps

[step 1] Using (E)-2-(8-bromomethyl-6,11-dihydrodibenzo[b,e]oxepin-11-ylidene)acetonitrile (1.5 g, 4.6 mmol) obtained in Reference Example B13 and 4-methyl-2-propylbenzimidazole (EP400835; 842 mg, 4.83 mmol) and in the same manner as in Example 92, step 1, (E)-2-{8-(4-methyl-2-propylbenzimidazol-1-yl)methyl-6,11-dihydrodibenzo[b,e]oxepin-11-ylidene}acetonitrile (1.47 g, 76%) was obtained. [step 2] (E)-2-{8-(4-Methyl-2-propylbenzimidazol-1-yl)methyl-6,11-dihydrodibenzo[b,e]oxepin-11-ylidene}acetonitrile (150 mg, 0.34 mmol) obtained in step 1 was dissolved in ethanol (1.8 mL), hydroxylamine (50% aqueous solution, 1.1 mL, 17.9 mmol) was added, and the mixture was stirred under reflux for 18 hr. Water was added to the mixture, and the mixture was extracted with chloroform. The organic layer was dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The obtained residue was dissolved in dichloromethane (1.8 mL), triethylamine (75 μL, 0.54 mmol) and ethyl chlorocarbonate (51 μL, 0.54 mmol) were added at 0° C., and the mixture was stirred at room temperature for 30 min. Water was added to the mixture, and the mixture was extracted with chloroform. The organic layer was dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The obtained residue was dissolved in toluene (0.9 mL) and THF (0.9 mL), potassium tert-butoxide (80 mg, 0.72 mmol) was added, and the mixture was stirred at room temperature for 20 min. 5% Aqueous citric acid solution was added to the mixture, and the mixture was extracted with chloroform. The organic layer was dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (hexane/ethyl acetate=70/30 to 10/90) to give the title compound (compound 104) (119 mg, 70%).

Provenance & Evidence