5-BROMO-2,3-DIHYDROBENZO[B]FURAN-7-BORONIC ACID synthesis

Yield:923297-52-3 76%

Reaction Conditions:

Stage #1: 4-bromopyridin;tetrakis(triphenylphosphine) palladium⁽⁰⁾ in 1,2-dimethoxyethane at 50; for 0.166667 h;
Stage #2: (5-bromo-2,3-dihydro-1-benzofuran-7-yl)boronic acidwith sodium carbonate in 1,2-dimethoxyethane;ethanol;water at 110; for 2 h;Heating / reflux;

Steps:

70 4-(5-Bromo-2,3-dihydro-benzofuran-7-yl)-pyridine

4-Bromopyridine or hydrochloride salt thereof was dissolved in DME under argon and Pd(Ph₃P)₄ (3 mol %) was added. The mixture was stirred for 10 min at 50° C. To this solution was added (commercially available) 5-bromo-2,3-dihydrobenzo[b]furan-7-boronic acid dissolved in a minimum amount of EtOH/DME 1:2 followed by 2N Na₂CO₃. The reaction mixture was refluxed (110° C.) under stirring for 2 h. The flask was cooled to RT, the mixture was treated with sat. aq. NH₄Cl solution and extracted with CHCl₃. Evaporation and purification by SiO₂ gel chromatography (hexane/ethyl acetate: 4/1) gave the title compound in 76% yield. ES-MS m/e (%): 275.9 (M+H⁺).

References:

US2007/27163,2007,A1 Location in patent:Page/Page column 42