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Abstract
Preparation of oxo-2 alkylphosphonates by anionic route is a process of limited scope. The low yields often encountered in the initial phosphonylation step are certainly due to regeneration of the departure phosphonate through acid–base exchanges. This drawback can be overcome by proper choice of the metalating agent. The use of LDA [(i-C3H7)2NLi] makes the procedure efficient and most stoechiometric, and it lends itself to the preparation of a wide range of β-ketophosphonates free of by-products.
La préparation des oxo-2 alkylphosphonates par voie anionique est un procédé de portée limitée. La régénération du phosphonate de départ par reprotonation en est très certainement responsable. Un choix judicieux de l ' agent de métallation permet de surmonter cet inconvénient. L ' addition au milieu réactionnel de DIPAL [(i-C3H7)2NLi] rend la réaction quasiment quantitative et stoechiométrique en phosphonate et précurseur de carbonyle.