Investigation on the Formation and Hydrolysis of N,N-Dimethylcarbamoyl Chloride (DMCC) in Vilsmeier Reactions Using GC/MS as the Analytical Detection Method

The formation of N,N-dimethylcarbamoyl chloride (DMCC) in Vilsmeier reactions (VRs) and the hydrolysis of DMCC during aqueous workup were investigated. The amount of DMCC formed was dependent on the chlorination reagent. The activity order was found to be: thionyl chloride > oxalyl chloride > phosphorus oxychloride. The concentrations of DMCC found in the tested reactions were normally at a level of 0−20 ppm. In the presence of a base the level was higher. DMCC hydrolyzed quickly under aqueous workup conditions. No more than 3 ppm of DMCC could be detected in the product after aqueous workup of the tested VR. Our results clearly indicate that by following the described procedure for VR it is perfectly safe from the health risk point of view to operate this chemistry when preparing compounds for pharmaceutical use. A very useful analytical procedure for detection and quantification of trace amounts of DMCC formed in the VR was developed. The method was based on derivatization of DMCC with ethanol to form e...