Carbon Dioxide → trichloroethyl N-benzylidene-alpha-amino-diethylphosphonoacetate

Participants

Reaction Conditions

Reaction Steps

A solution of diethyl N-benzylidene-aminomethylphosphonate (12.738 g., 50 mmole) in dry tetrahydrofuran (250 ml.) is stirred in a dry ice-acetone bath and under a nitrogen atmosphere. Phenyllithium (25 ml. of a 2.0 M solution in 7:3 benzene-ethyl ether) is added via syringe. The resulting burgundy solution is stirred for 30 minutes at -78°C., then treated dropwise over 45 minutes with a solution of 2,2,2-trichloroethyoxycarbonyl chloride (5.30 g., 25 mmole) in dry tetrahydrofuran (50 ml.). After stirring the mixture for an additional 2 hours at -78°C., the dry ice bath is replaced by an ice water bath and stirring is continued for 1 hour. Evaporation of the solvent in vacuo leaves a yellow foam which is partitioned between ethyl ether (250 ml.) and aqueous phosphate (50 ml. of 1M pH 3 phosphate + 50 ml. water). The aqueous portion is separated and extracted with ethyl ether (2 × 50 ml.). The combined ethereal solution is washed with saturated brine (100 ml.), dried over magnesium sulfate, and evaporated in vacuo to yield a cloudy, yellow oil (17.1 g.). The crude product is purified by chromatography on silica gel (430 g., packed under ethyl ether). Elution with ethyl ether affords trichloroethyl N-benzylidene-α-amino-diethylphosphonoacetate (7.058 g.) as a yellow oil.

Provenance & Evidence