Ethyl orthoformate → 6-tosyl-6H-pyrrolo[2,3-e][1,2,4]triazolo[4,3-a]pyrazine

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Reaction Conditions

Reaction Steps

Triethyl orthoformate (76.0 mL, 456 mmol) was added to a mixture of 2-hydrazinyl-5-tosyl-5H-pyrrolo[2,3-b]pyrazine (13.8 g, 45.4 mmol, Example #1, Step D) and DMF (45 mL) under nitrogen. A reflux condenser was attached and the mixture was warmed to about 100° C. After about 17 h, the solution was allowed to cool to ambient temperature. The volatiles were removed under reduced pressure. The residue was slurried in water (100 mL) and then filtered, rinsing with water. The aqueous phase was extracted with EtOAc (200 mL). The organics were dried over anhydrous Na2SO4, filtered, and concentrated. The material was combined with the precipitate and then purified by silica gel chromatography eluting with a gradient of 0-5% MeOH in DCM to give 6-tosyl-6H-pyrrolo[2,3-e][1,2,4]triazolo[4,3-a]pyrazine (10.4 g, 73%): LC/MS (Table 1, Method n) Rt=0.59 min; MS m/z 314 (M+H)+.

Provenance & Evidence