B-(9-methyl-9H-carbazol-3-yl)Boronic acid synthesis

Yield:1039761-02-8 54%

Reaction Conditions:

Stage #1: 3-iodo-9-methyl-9H-carbazolewith n-butyllithium in tetrahydrofuran;hexane at -78; for 1 h;
Stage #2: Trimethyl borate in tetrahydrofuran;hexane at -78 - 20; for 1 h;
Stage #3: with hydrogenchloride;water in tetrahydrofuran;hexane;

Steps:

1

Synthesis of Intermediate D; Intermediate C (2.25 g, 7.34 mmol) was added to THF (50 ml), and n-butyllithium (2.5M in hexane) (3.9 ml, 9.55 mmol) was dropwise added thereto at -78° C. The reaction mixture was stirred for one hour, and trimethylborate (2.5 ml, 22.0 mmol) was added thereto. The reaction solution was heated to room temperature, stirred for one hour, and hydrolyzed with a 2N HCl solution. The aqueous layer was extracted three times with ethylacetate (20 ml). The collected organic layer was dried over magnesium sulfate to evaporate a solvent. The resultant residue was purified by silica gel column chromatography to give intermediate D as a white solid (0.89 g, yield: 54%). The structure of intermediate D was determined by ¹H NMR. ¹H NMR (CDCl₃, 300 MHz) δ (ppm) 8.11 (d, 1H), 8.09 (s, 2H), 7.93 (dd, 1H), 7.67 (dd, 1H), 7.58 (d, 1H), 7.44-7.37 (m, 1H), 7.32-7.25 (m, 2H), 30.7; ¹³C NMR (CDCl₃, 100 MHz) δ (ppm) 144.2, 140.1, 131.2, 130.6, 129.8, 129.5, 128.4, 127.2, 126.4, 125.8, 120.4, 119.7, 109.3, 100.1, 95.5, 86.5, 31.1.

References:

US2008/174237,2008,A1 Location in patent:Page/Page column 12