Triethylamine → 8-carbamoyl-7-chloro-6-phenyl-3,4-dihydro-1H-pyrrolo[1,2-a]pyrazine-2-carboxylic acid phenyl ester

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Reaction Conditions

Reaction Steps

A suspension of 7-chloro-6-phenyl-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-8-carboxylic acid amide trifluoroacetic acid salt (100 mg, Reference Example 1) in dry dichloromethane (5 mL) was treated with dry triethylamine (0.11 mL). The resulting solution was then cooled to −40° C. and treated with a solution of phenyl chloroformate (32 μL, redistilled) in dry dichloromethane (5 mL) whilst maintaining the temperature at 40° C. After stirring at −40° C. for a further 30 minutes the reaction mixture was allowed to warm to room temperature and then washed three times with water (20 mL). The organic phase was dried over magnesium sulfate and the solvent then removed under reduced pressure. The residue was subjected to column chromatography on silica eluting with a mixture of pentane and ethyl acetate (9:11, v/v) to give 8-carbamoyl-7-chloro-6-phenyl-3,4-dihydro-1H-pyrrolo[1,2-a]pyrazine-2-carboxylic acid phenyl ester (40 mg) as a white solid, m.p. 196–198° C. [Elemental analysis: C, 63.52; H, 4.45; N, 10.31%; Calculated for C21H18ClN3O3: C, 63.72; H, 4.58; N, 10.62%].

Provenance & Evidence