Triphenylphosphine → (S)-7-bromo-3-methyl-1-tosyl-1,2,3,4-tetrahydroquinoxaline

Participants

Reaction Conditions

Reaction Steps

A 3-L, three-necked, round bottomed flask fitted with a nitrogen inlet, overhead stirrer, and thermocouple was charged with (S)-N-(5-bromo-2-(1-hydroxypropan-2-ylamino)phenyl)-4-methylbenzenesulfonamide (77.0 g, 193 mmol), THF (1925 mL), and triphenylphosphine (60.7 g, 231 mmol). The solution was cooled to 0° C., and diisopropyl azodicarboxylate (DIAD) (41.2 mL, 212 mmol) was slowly added while maintaining the internal temperature below 7° C. The reaction mixture stirred at 0° C. for 1.5 h and was then warmed to room temperature. The mixture was concentrated and the residue was purified by column chromatography on silica gel (eluting with dichloromethane). The product-containing fraction were combined and concentrated under reduced pressure. The material was treated with a mixture of 4:1 hexanes-dichloromethane, and the slurry was stirred for 3 h and then filtered. The solids were rinsed with cold (ca. 0° C.) solution of 4:1 hexanes-dichloromethane (50 mL) and dried to afford (S)-7-bromo-3-methyl-1-tosyl-1,2,3,4-tetrahydroquinoxaline (61.8 g, 84%) as a white solid. MS (ESI, pos. ion) m/z 381 [M+1]+.

Provenance & Evidence