Trimethyl borate → [2-Borono-4-(trifluoromethyl)phenoxy]-acetic acid

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Reaction Conditions

Reaction Steps

A solution of sec-butyllithium (66 ml, 1.4M in cyclohexane) was added dropwise over 10 min to a stirred solution of the product from step (iii) (9.44 g) in THF (100 ml) at −78° C. After 3 h the mixture was warmed to −40° C. for 5 min, then cooled to −78° C. Trimethylborate (14.1 ml) was added, then after 10 min the reaction quenched with 2M hydrochloric acid. The mixture was warmed to RT and the organic phase separated. The aqueous layer was extracted with ethylacetate, the organics combined and evaporated under reduced pressure. The residue was dissolved in methanol (500 ml) then bondelut-NH2 resin(180 g) added and the mixture swirled for 0.5 h then filtered. The resin was washed with 10% acetic acid/methanol, the washings then evaporated under reduced pressure and dried under high vacuum. The residue was dissolved in methanol (50 ml), tetrahydrofuran (50 ml) and saturated aqueous sodium hydroxide solution (2 ml), left for 30 min then 2M hydrochloric acid (50 ml) added and the organics evaporated under reduced pressure. The residual aqueous layer was extracted with ethylacetate, the organics separated, dried and evaporated under reduced pressure, yield 5.05 g.

Provenance & Evidence