Ethyl chloroformate → HCID 67200254, compound

Participants

Reaction Conditions

Reaction Steps

To a solution of 94.1 g of 3-amino-4,5,6,7-tetrahydro-1H-pyrazolo[4,3-c]pyridine-5-carboxylic acid tert-butyl ester in 1.7 L of THF were added 135 mL of N,N-diisopropylethylamine. A solution of 37.6 mL of ethyl chloroformate in 300 mL of THF was added dropwise at 0° C. during 75 min. The mixture was stirred at 0° C. for 30 min. then evaporated under vacuum. The residue was taken-up with 1 L of water and extracted with ethyl acetate. The combined organic extracts were washed with 500 mL brine, dried over sodium sulfate, and evaporated to dryness. The crude mixture of isomers was purified by silica gel flash-chromatography, using a starting 87:13 mixture of dichloromethane-ethyl acetate as eluant, and increasing gradually the percentage of ethyl acetate up to 50%. The fractions containing the same isomer were evaporated to give 61.6 g of 3-amino-4,5,6,7-tetrahydro-2H-pyrazolo[4,3-c]pyridine-2,5-dicarboxylic acid 5-tert-butyl ester 2-ethyl ester.

Provenance & Evidence