How is 1-Ethyl-1,4-diazepane dihydrochloride (CAS: 1219843-83-0) typically synthesized?

1-Ethyl-1,4-diazepane dihydrochloride is typically synthesized by the reaction of 1,4-diazepane with ethyl chloroformate in the presence of a base like triethylamine. The reaction is carried out under anhydrous conditions to avoid hydrolysis. The yield of the product is usually high, and the reaction is selective, leading to a pure product in a single step.