2-Cyanoethyl and p-nitrophenethyl α-hydroxyimino- and α-methoxyimino-phosphonates: potential precursors of metaphosphate anion

Abstract

Methyl benzoylphosphonochloridate 3 reacted with 2-cyanoethanol or p-nitrophenethyl alcohol to yield methyl 2-cyanoethyl benzoylphosphonate 4a or methyl p-nitrophenethyl benzoylphosphonate 4b. Ketones 4a and 4b were converted into the corresponding oximes, 5a and 5b as a mixture of E and Z isomers, by hydroxylamine. Oximes 5a and 5b were demethylated by treatment with sodium iodide or lithium bromide to give the corresponding monester monosalts 6a and 6b. Reaction of lithium 2-cyanoethyl or p-nitrophenethyl benzoylphosphonate with methoxylamine afforded the respective oxime methyl ether salts 8a and 8b as predominantly E isomers. Base treatment of 6a and 6b caused their dealkylation to the anion of α-hydroxyiminobenzylphosphonic acid 9 which did not decompose further. In contrast, 8a and 8b in aqueous base gave the dianion of α-methoxyaminobenzylphosphonic acid 10, which slowly fragmented to benzonitrile and phosporic acid. The fragmentation is interpreted in terms of a dissociative mechanism involving the formation of metaphosphate anion.