Synthesis of nitroxyethylnitramine (NENA) plasticizers and dinitroxydiethylnitramine (DINA) in continuous flow**

Abstract

Nitroxyethylnitramines (NENAs) and dinitroxydiethylnitramine (DINA) are useful energetic plasticizer components in propellants and explosives. However, their synthesis at large scale can be delicate because it involves two dissimilar nitration reactions: nitrate ester formation and halide-catalyzed nitramine formation. Consequently, these preparations, and particularly when conducted in a single-stage/pot operation, are problematic with respect to issues such as process safety (heat transfer, temperature control), product purity, replicability and operability. Herein, we briefly review procedures for preparation of NENAs and/or DINA and then report on our own work on continuous flow synthesis of this family of nitramine-nitrate ester compounds. We find them to be particularly suited for flow synthesis. Our studies are first and foremost distinguished from previous ones by focusing on the use of acetyl chloride as a metal-free, convenient chloride catalyst and the application of glacial acetic acid as a salt-forming secondary amine solvent, thus facilitating pumping of the amino alcohols and preventing local exotherms. We have also incorporated post-reaction simmering of the final flow effluent to enhance product purities by removal of nitroso impurities.