Cyclic Oligophosphonic Anhydrides Stable in Aqueous Media

Depending on reaction conditions, the phosphonylation of N-alkylacetamides with H3PO3-P C I3 in B-HC1 media (B = Py, Bu3N) gives either l-alkylaminoethylidene-l,l-bisphosphonic acids (la—e) or previously unknown l-alkylaminobutane-l,l,3,3-tetrayl-tetrakisphosphonic dianhydrides (2a-e). The latter convert into monocyclic forms (3a-e) under mild acidic hydrolysis. Acyclic forms (4a-e) cannot be isolated. In the presence of higher N,N-dialkylamides the phosphonylation of acetamides affords the higher dianhydrides (2f-h). Strong acidic hydrolysis of 2 or 3 yields 3,3-diphosphonocarboxylic acids (5a-c). Reacting with H3P 0 3-P H al3 in B HHal (Hal = Cl, Br), the amides R 'C O N H R 2 (R 1 ^ h , Me; R 2 = Alk, H) give both N-alkyl(or N-unsubstituted) l-am inoalkylidene-l,l-bis-phosphonic acids (6a-j) and their cyclic dimeric anhydrides (7a-g, i, j).