Synthesis of 1-Aminophosphonic Acid Derivatives via Acyliminophosphonic Esters 1-Acylaminomethylphosphonates 1 on reaction with N-bromosuccinimide yield 1-acylamino-1-bromomethylphosphonates 2, which on treatment with tertiary amines are converted into acyliminophosphonates 3. The latter react in situ with nucleophiles like enamines, ynamines, aryl, alkenyl and alkynyl Grignard compounds to give derivatives of 1-acylaminomethylphosphonates. Reaction of bromides 2 with phosphites and triphenylphosphine yields compounds of type 8 and 10, respectively.