N-Phosphorylated Aziridines. The Reaction of 2-Iodoalkyl Azides with Phosphines and Phosphites

2-Iodoalkyl azides react readily and stereospecifically with trivalent phosphorus nucleophiles by attack on azide to form N-phosphorylated aziridines. The use of triphenylphosphine gives aziridinyltriphenylphosphonium iodide salts 5. When phosphites were used these salts underwent further transformations in situ leading to aziridinephosphonates 7, 10, or 11. The structure of these compounds was proved by an independent synthesis. LAH reduction of 5 or 7 proceeded with P-N bond cleavage. This reaction sequence was shown to be a convenient method of aziridine synthesis in particular for cases where other methods failed. Dimethyl N-(2,2-diphenyl-aziridinyl)phosphonate 20 rearranges on standing to an enamine phosphonate 23. The use of nmr in distinguishing between aziridinyl and open chain isomers is discussed.