144108-12-3Relevant articles and documents
Investigation of reactive intermediates and reaction pathways in the coupling agent mediated phosphonamidation reaction
Fredriksen, Kim Alex,Amedjkouh, Mohamed
supporting information, p. 474 - 482 (2016/02/18)
The preparation of carboxamides through the coupling agent mediated reaction of carboxylic acids and amines is one of the most frequently employed reaction types of modern organic synthesis and has largely replaced older methods of amide formation based on reactive acyl chloride intermediates. However, the preparations of analogous phosphonamidates still rely on the use of phosphonochloridate intermediates - a method that is incompatible with sensitive functional groups. Herein, we present a comprehensive study in which different coupling agents are tested in the phosphonamidation reaction. The procedures, parallel to those typically applied to the preparation of carboxamides, were generally unsuccessful with regard to the coupling reactions of monoesters of phosphonic acids and amines, with the exception of those mediated by (benzotriazol-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate (PyBOP). The implementation of a preactivation period in the absence of the amine coupling partner allowed for efficient phosphonamidate formation with coupling agents such as (1-cyano-2-ethyoxy-2-oxoethylideneaminooxy)dimethylamino-morpholino-carbenium hexafluorophosphate (COMU), [ethyl cyano(hydroxyimino)acetato-O2]tri-1-pyrrolidinylphosphonium hexafluorophosphate (PyOxim), dicyclohexyl carbodiimide (DCC), N,N′-diisopropylcarbodiimide (DIC), and N,N,N′,N′-tetramethyl-O-(1H-benzotriazol-1-yl)uronium hexafluorophosphate (HBTU). The reactive intermediates observed by 31P NMR analysis were individually synthesized and examined to understand their influence on the reaction. A phosphonamidation reaction that uses (1-cyano-2-ethyoxy-2-oxoethylideneaminooxy)dimethylamino-morpholino-carbenium hexafluorophosphate (COMU) to mediate the coupling of monoalkyl esters of phosphonic acids and amines was developed. A preactivation period without the amine was needed to obtain the product. Using this step allowed for other coupling agents to be successfully used in the reaction.
The Synthesis of Phosphonate Esters, an Extension of the Mitsunobu Reaction
Campbell, David A.
, p. 6331 - 6335 (2007/10/02)
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