Ammonium Chloride → (+/-)-(3aR*,7aS*)-7a-(4-bromothiophen-2-yl)-hexahydropyrano[3,4-c]isoxazole

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Reaction Steps

n-Butyllithium (2.63 M, 2.99 ml) was added dropwise to a solution of 2,4-dibromothiophene (2.00 g) in toluene-THF (10:1) (22 ml) at −78° C. After stirring at the same temperature for one hour, a solution of (±)-3,3a,4,5-tetrahydro-7H-pyrano[3,4-c]isoxazole obtained in Preparation Example 1-(2) (500 mg) in toluene-THF (10:1) (10 ml) and a boron trifluoride-diethyl ether complex (990 μl) were added dropwise at the same time. After stirring at the same temperature for two hours, an ammonium chloride solution was added to terminate the reaction. The aqueous layer was extracted with ethyl acetate, and the organic layer was dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure and the residue was purified by silica gel column chromatography to obtain the title compound (700 mg).

Provenance & Evidence