2-Methoxypropene → (Z)-2-(4,5-difluoro-2-hydroxybenzoyl)-3-hydroxypyridine O-t-butyloxime

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Reaction Steps

A mixture of 2-bromo-4,5-difluorophenol (7.27 g) and 2-methoxypropene (10 ml) was stirred for one hour at room temperature, followed by adding diethyl ether (75 ml) and cooling to -78° C. To the mixture was added dropwise, under argon atmosphere, a 1.6M solution of n-butyl lithium hexane solution (25 ml), followed by stirring for one hour. To the reaction mixture was then added dropwise 2-cyano-3-trimethylsilyloxypyridine (7.01 g). The cooling bath was removed, and the mixture was stirred for 3 hours while warming up to room temperature. To the reaction mixture was added ethanol (10 ml) to quench the reaction. The solvent was distilled off under reduced pressure. To the residue were added triethylamine (20 ml), O-t-butylhydroxylamine hydrochloride (3.06 g) and ethanol (50 ml). The mixture was heated for 5 hours under reflux. The solvent was distilled off. To the residue were added chloroform and water for extraction. The organic layer was dried (anhydrous magnesium sulfate), and the solvent was distilled off under reduced pressure. The residue was purified by means of a silica gel column chromatography (eluted with ethyl acetate/hexane) to give (Z)-2-(4,5-difluoro-2-hydroxybenzoyl)-3-hydroxypyridine O-t-butyloxime (5.19 g) and (E)-2-(4,5-difluoro-2-hydroxybenzoyl)-3-hydroxypyridine O-t-butyloxime (1.49 g) (Compounds 34 and 35).

Provenance & Evidence