The preparation of N-substituted aminomethylidenebisphosphonates and their tetraalkyl esters via reaction of isonitriles with trialkyl phosphites and hydrogen chloride. Part 1

The reaction of isonitriles with trialkyl phosphites in the presence of hydrogen chloride gives tetraalkyl N-substituted aminomethylidenebisphosphonates via N-methylideneaminium (isonitrilium) salts. Hydrolysis or dealkylation of these tetraalkyl esters gives N-substituted aminomethylidenebisphosphonic acids in high yields.