Potassium Carbonate → 2-(4,4-Dimethyl-2-oxo-1,4-dihydro-2H-benzo[d][1,3]oxazin-6-yl)-pyrrole-1-carboxylic acid tert-butyl ester

Participants

Reaction Conditions

Reaction Steps

A solution of 6-bromo-4,4-dimethyl-1,4-dihydro-benzo[d][1,3]oxazin-2-one (5.0 g, 20 mmol) and tetrakis(triphenylphosphine)palladium(0) (580 mg, 0.5 mmol) in toluene (200 mL) was stirred under a flow of nitrogen for 25 min. To the solution was added sequentially 1-tert-butoxycarbonylpyrrole-2-boronic acid (8.24 g, 39 mmol) in absolute ethanol (50 mL) and potassium carbonate (5.39 g, 39 mmol) in water (50 mL). The mixture was heated to 80° C. for 16 h and allowed to cool. The reaction mixture was poured into aqueous saturated sodium bicarbonate solution (200 mL) and extracted with ethyl acetate (3×200 mL). The organic layers were combined, washed with water (200 mL) and brine (100 mL) and dried over magnesium sulfate. The solution was filtered, concentrated in vacuo, and the residue was purified by flash column chromatography on silica gel (30% ethyl acetate/hexane) to give 2-(4,4-dimethyl-2-oxo-1,4-dihydro-2H-benzo[d][1,3]oxazin-6-yl)-pyrrole-1-carboxylic acid tert-butyl ester (4.0 g, 58%) as a tan solid, mp 172-173° C.

Provenance & Evidence