Cesium carbonate → (RS)-3-(2-oxo-3-trityl-2,3-dihydro-benzooxazol-6-yl-sulfanyl)-pyrrolidine-1-carboxylic acid tert-butyl ester

Participants

Reaction Steps

Tris(dibenzylideneacetone)dipalladium chloroform complex (14 mg, 13.5 □mol) and 1,1′-bis(diphenylphosphino)ferrocene (30 mg, 54.1 □mol) in degassed and dry toluene (2 ml) were stirred at room temperature until the solution turned orange (15 minutes). 6-Bromo-3-trityl -3H-benzooxazol-2-one (0.2 g, 0.44 mmol), Cs2CO3 (0.22 g, 0.68 mmol) and (RS) -3-mercapto-pyrrolidine-1-carboxylic acid tert-butyl ester (0.1 g, 0.49 mmol) in toluene (0.5 ml) were successively added. After 4 hours stirring at 100° C., the reaction mixture was cooled to room temperature and concentrated. The residue was chromatographed over silica gel (hexane-ethylacetate 9:1 then 1:1) to provide (RS)-3-(2-oxo-3-trityl-2,3-dihydro-benzooxazol-6-yl-sulfanyl)-pyrrolidine-1-carboxylic acid tert-butyl ester (0.19 g 7 77%) as a white foam, MS: m/e=596.1 (M+NH4+).

Provenance & Evidence