3-FLUORO-4-(METHYLSULFONYL)PHENYLBORONIC ACID synthesis

Yield:648904-83-0 42%

Reaction Conditions:

Stage #1: 2-(3-fluoro-4-methanesulfonyl-phenyl)-4,4,5,5-tetramethyl-[1,3,2]dioxaborolanewith sodium periodate in tetrahydrofuran;water; for 2 h;
Stage #2: with hydrogenchloride in tetrahydrofuran;diethyl ether;water; for 12 h;

Steps:

4

Combine 4-bromo-2-fluorothioanisole (US Patent No. 6,307, 047,2. 7 g, 12 mmol), oxone (38 g, 62 mmol) and methanol (200 mL) and stir for 12 hours. Filter through a pad of silica gel and elute with ethyl acetate (500 mL). Evaporate solvent and partition between dichloromethane (200 mL) and water (100 mL). Separate the layers, wash the organic layer with saturated aqueous NaHC03 (10 mL), brine (10 mL), dry with MgS04, filter, and concentrate in vacuo. Wash the crude solid with hexane (20 mL), ether (10 mL) and dry in vacuo to obtain 2.4 g of 4-bromo-2-fluoro-1-methanesulfonyl-benzene (78%). Combine 4-bromo-2-fluoro-1-methanesulfonyl-benzene (1.7 g, 6.7 mmol), [1, 1'- bis (diphenylphosphino) ferrocene] dichloropalladium (II) complex with dichloromethane (Pd (dppfjCl2 CH2Cl2, 164 mg, 0.20 mmol), bis (pinacolato) diboron (1.79 g, 7.0 mmol), potassium acetate (2 g, 20 mmol) and dimethylsulfoxide (DMSO, 100 mL). Heat the reaction mixture at 90°C for 1 hour. Cool to room temperature and dilute with ethyl acetate (20 mL). Wash with brine (10 mL), dry with MgS04, filter, and concentrate in vacuo. Chromatograph the residue on a Si02 column eluting the material with ethyl acetate in hexane (30%) to give 1.74 g (80%) of 2- (3-fluoro-4-methanesulfonyl-phenyl)- 4,4, 5, 5-tetramethyl-[1, 3, 2] dioxaborolane. Combine 2- (3-fluoro-4-methanesulfonyl-phenyl)-4, 4,5, 5-tetramethyl- [1, 3,2] dioxaborolane (222 mg, 0.74 mmol), NaIO4 (474 mg, 2. 2 mmol), tetrahydrofuran (THF, 4 mL) and water (1 mL). Stir for 2 hours and add 2M HC1 in diethyl ether (0.2 mL). Stir another 12 hours and filter away the solid. Wash the filtrate with brine (10 mL), dry with MgS04 and evaporate the solvent. Wash the solid with hexane (2 x 10 mL) and ether (10 mL). Dry the solid under vacuum to obtain 68 mg of the title compound (42%).

References:

WO2004/9086,2004,A1 Location in patent:Page/Page column 22-23