Chemical Properties
Clear and colorless liquid
Uses
1-Chloroethyl chloroformate was used:
- for N-demethylation reaction during determination of multiple drugs of abuse in biological fluids using capillary electrophoresis with native fluorescence and laser-induced fluorescence detection
- as catalyst in chemoselective desilylation of silyl-protected alcohols
- as reagent in N-demethylation of tertiary amines to produce drug metabolite reference material for forensic toxicological applications
- as reagent to cleave benzhydryl groups from amines
Uses
Reagent for the selective N-dealkylation of tertiary amines in high yields.
Preparation
1-Chloroethyl chloroformate is obtained by stirring phosgene and acetaldehyde in the presence of benzyltributylammonium chloride, followed by distillation (96% yield).
Reactivity Profile
1-chloroethyl chloroformate was found to be the potential reagent of choice for the N-demethylation of tertiary amines. The reaction was performed by refluxing in dry 1,2-dichloroethane under nitrogen, and the carbamate intermediate was hydrolysed by treatment with methanol[1].
The debenzylation conditions were mediated by 1-chloroethyl chloroformate (green), which gave the expected secondary amine 3 (blue) an excellent yield. The debenzylation proceeds presumably via a carbamate intermediate following the reaction of the starting material 6 with 1-chloroethyl chloroformate and loss of benzyl chloride. Subsequent decarboxylation, promoted by excess methanol and reflux conditions, produced the desired secondary amine 3.
Synthesis
An initiator solution was formed by dissolving 0.33 gram of 2,2'-azobis(2-methylpropanenitrile) in 61 grams of ethyl chloroformate. The initiator solution was charged to the syringe. The flask was charged with 590 grams of ethyl chloroformate. The flask was then heated to obtain close to maximum reflux without flooding. The syringe pump was set to feed approximately 5 millilitres of the initiator solution per hour. The introduction of molecular chlorine gas through the first inlet at 0.47 gram per minute was then begun. During the reaction, the condenser functioned as a total reflux condenser. The chlorine introduction was terminated twelve hours later, and the reaction mixture was allowed to cool. The final reaction product weighed 806 grams. Gas chromatographic analysis of the reaction product showed it to contain 18.8 area percent of ethyl chloroformate, 45.4 area percent of 1-chloroethyl chloroformate, 34.7 area percent of 2-chloroethyl chloroformate, and 1.06 area percent of dichlorinated ethyl chloroformate.
References
[1] Anna Pelander, Tapio A. Hase, Ilkka Ojanper . “Preparation of N-demethylated drug metabolites for analytical purposes using 1-chloroethyl chloroformate.” Forensic science international 85 3 (1997): Pages 193-198.
[2] Katrina A Badiola. “Efficient Synthesis and Anti-Tubercular Activity of a Series of Spirocycles: An Exercise in Open Science.” PLoS ONE (2014): e111782.
