Hydrochloric Acid → [5-(Trifluoromethyl)pyridin-3-yl]boronic acid

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Reaction Conditions

Reaction Steps

Triethylborate (24 ml, 139 mmol) is added to a solution of 3-bromo-5-trifluoromethyl-pyridine (30 g, 133 mmol) in THF (300 ml) and the resulting pale yellow solution is cooled to −78° C. A solution of 1.6 M n-butyl lithium in hexanes (97 ml, 139 mmol) is added via cannula dropwise over 40 minutes, keeping the temperature below −65° C. Once addition is complete, the reaction mixture is allowed to warm slowly to room temperature and stirred for 1 hour. 1M HCl (200 ml) is added and the reaction mixture stirred for 15 minutes. The layers are separated and the organic layer is washed with 1M HCl (200 ml). The aqueous layers are combined and washed with EtOAc (2×250 ml). The pH of the aqueous phase is adjusted by the addition of 2M NaOH, and extracted with EtOAc (2×250 ml). Concentration in vacuo affords a solid, which is recyrstallised from EtOAc/iso-hexane to yield the title compound as a yellow solid [M+H]+ 192.

Provenance & Evidence