Pyridine → (S)-1-(6-bromo-2-methyl-4-tosyl-3,4-dihydroquinoxalin-1(2H)-yl)ethanone

Participants

Reaction Conditions

Reaction Steps

A 2-L, three-necked, round bottomed flask fitted with a nitrogen inlet, overhead stirring, and thermocouple was charged with (S)-7-bromo-3-methyl-1-tosyl-1,2,3,4-tetrahydroquinoxaline (45.0 g, 118 mmol), dichloromethane (900 mL), and pyridine (14.32 mL, 177 mmol). The mixture was cooled to 0° C. and acetyl chloride (10.07 mL, 142 mmol) was added slowly while maintaining the internal temperature below 10° C. The reaction mixture was held cold (ca. 30 min) and then warmed to rt. After 1 h, the reaction was diluted with dichloromethane (200 mL), and the solution was washed with 1 M aqueous HCl (2×100 mL) and water (100 mL). The organic layer was concentrated under reduced pressure and the crude product was purified by column chromatography on silica gel (eluting with 3:1 dichloromethane-ethyl acetate) to afford (S)-1-(6-bromo-2-methyl-4-tosyl-3,4-dihydroquinoxaline-1(2H)-yl)ethanone (54.15 g, 108%), which contained 4.1 wt % ethyl acetate, as a colorless to yellow oil. MS (ESI, pos. ion) m/z 424 [M+1]+.

Provenance & Evidence