4-Toluenesulfonyl chloride → 2-Bromo-5-((4-methylphenyl)sulfonyl)-5H-pyrrolo(2,3-b)pyrazine

Participants

Reaction Conditions

Reaction Steps

A solution of 2-bromo-5H-pyrrolo[2,3-b]pyrazine (78.0 g, 394 mmol, Ark Pharm) in anhydrous DMF (272 mL) was added drop-wise over about 60 min to a stirred suspension of NaH (60% dispersion in mineral oil, 12.8 g, 532 mmol) in anhydrous DMF (543 mL) at about 0-5° C. The brown reaction solution was stirred for about 30 min at about 0-5° C. then a solution of p-toluenesulfonyl chloride (94.0 g, 492 mmol) in anhydrous DMF (272 mL) was added drop-wise over about 60 min at about 0-5° C. The reaction mixture was stirred at about 0-5° C. for about 1 h then allowed to warm to ambient temperature and stirred for about 18 h at ambient temperature. The reaction mixture was poured slowly into ice water (6 L), followed by the addition of aqueous NaOH (2.5M, 50.0 mL, 125 mmol). The precipitate was collected by filtration and stirred with cold water (3×200 mL). The solid was collected by filtration and dried to constant weight in a vacuum oven at about 55° C. to yield 2-bromo-5-tosyl-5H-pyrrolo[2,3-b]pyrazine (134.6 g, 97%) as a pale beige solid: LC/MS (Table 2, Method d) Rt=1.58 min; MS m/z: 352/354 (M+H)+.

Provenance & Evidence