Ethyl chloroformate → HCID 11392958, compound

Participants

Reaction Steps

2,2,6,6-Tetramethylpiperidine (2.21 g, 15.6 mmol) was dissolved in 30 mL tetrahydrofuran and cooled down to −75° C. n-Butyllithium (9 mL, 14.3 mmol, 1.6M solution in n-hexane) was added while maintaining the temperature below −70° C. After 50 min., a solution of 3.2 g (13.0 mmol) 7-ethyl-indole-1-carboxylic acid tert-butyl ester in 15 mL tetrahydrofuran was added and the temperature again kept below −70° C. After 50 min., ethyl chloroformate (1.4 mL (14.3 mmol) was added and the temperature was allowed to rise to −50° C. After 1 h the reaction mixture was poured into 30 mL saturated aq. ammonium chloride solution and the phases separated. The aqueous phase was extracted once with 50 mL diethyl ether and the combined organic extractions were washed successively with saturated aq. ammonium chloride solution and water, dried over magnesium sulfate, filtered and evaporated. The crude reaction product was flash-chromatographed over silica gel (0.030–0.060 mm) with n-hexane/tert-butyl methyl ether (39/1) as eluant to give the product as a yellow oil (2.3 g, 56.2%). EI-MS: m/e=317.2 ([M])

Provenance & Evidence