Trimethyl borate → (3-Chlorophenyl)boronic acid

Participants

Reaction Conditions

Reaction Steps

A solution of trimethylborate in 200 mL of ethyl ether was cooled to -65° C. 3-Chlorobenzene magnesium chloride (0.8 M, 60 mL), i.e., a grignard reagent, was added to the solution in a dropwise manner over 20 minutes. The mixture was kept in the temperature range of -60° C. to -70° C. and stirred. After 30 minutes, the mixture was allowed to warm to 0° C. and stirred for 1 hour. The mixture was quenched with H2O (25 mL) and stirred at room temperature for 1 hour. The solvent was removed and the remaining mass was extracted with ethyl ether (3×100 mL). The organic layers were combined and washed with H2O (2×50 mL), dilute HCl (2×100 mL), H2O (2×50 mL) and brine (1×50 mL). The organic layer was dried with MgSO4 and concentrated, and 100 mL of hexanes was added, and the mixture stirred for 1 hour. The resultant white precipitate was filtered off and allowed to air dry, yielding 4.6 g of 3-chlorobenzene boronic acid, a compound of Formula 4 where R4 is 3-chlorophenyl, as a white solid.

Provenance & Evidence