Diisopropylaminoborane (2.4 mL, 2.4 mmol, 1.2 eq.) was added to a 50 mL round-bottomed flask fitted with a magnetic stir bar and fitted with a rubber septum. O-tolylmagnesium bromide (2 mL, 2.0 mmol, 1 eq.) was added dropwise over 5 min via syringe while stirring (ice bath) at 0C. After 1 hr, with the reaction still on ice, 3 M HCl (5 mL) was added dropwise over 5 min and stirred for 30 min. The reaction mixture was then refluxed for 15 min. After refluxing, the solution was transferred to a partition funnel and extracted with Et2O (2 15 mL). The organic layers were combined and extracted with 1 M HCl (4 15 mL), dried with anhydrous MgSO4 and evaporated in vacuum (25C, 1 Torr). A white powder cyclohexylboronic acid was obtained; 97% yield (0.497 g).
