Pyridine → (S)-isopropyl 7-bromo-4-(cyclopropanecarbonyl)-3-methyl-3,4-dihydroquinoxalin-1(2H)carboxylate

Participants

Reaction Conditions

Reaction Steps

A 100-mL round bottomed flask fitted with a nitrogen inlet and magnetic stir bar was charged with (S)-(6-bromo-2-methyl-3,4-dihydroquinoxalin-1 (2H)-yl)(cyclopropyl)methanone (0.62 g, 2.1 mmol), dichloroethane (25 mL), and pyridine (0.254 mL, 3.15 mmol). The mixture was cooled to 0° C. in an ice bath. A solution of isopropyl chloroformate (1 M in toluene, 2.52 mL, 2.52 mmol) was then added dropwise over several minutes. The reaction mixture was stirred for 30 min in an ice bath before warming to ambient temperature for 1 h. The reaction mixture was diluted with dichloromethane (20 mL) and washed with 1 M aqueous HCl solution (25 mL). The organic layer was separated and concentrated under reduced pressure. The oil was put through a silica pad using 1:1 hexane/ethyl acetate and the eluent was concentrated in vacuo. This afforded (S)-isopropyl 7-bromo-4-(cyclopropanecarbonyl)-3-methyl-3,4-dihydroquinoxalin-1(2H)carboxylate (0.83 g, 100%) as a solid, which was used directly in next step. MS (ESI, pos. ion) m/z 381, 383 [M+1]+.

Provenance & Evidence