Synthesis and Reactivity of Azidoalkylphosphonates, -Phosphinates and -Phosphine Oxides

This review will focus on the synthesis of α- and β-azidoalkylphosphonic and -phosphinic acids, -phosphine oxides and their derivatives as well as their reactions utilizing the azido group and/or phosphyl group. In the first part of this review synthetic routes to such azides will be reviewed. Generally, these compounds are achieved via nucleophilic substitution of hydroxy derivatives of phosphonates, -phosphinates, and -phosphine oxides by the Mitsunobu protocol or by the displacement of their sulfonates or halogen derivatives with azides. The ring-opening of phosphorus-containing oxiranes or cyclic vicinal sulfates with azides will also be discussed. Electrophilic azidation of the corresponding phosphorus- stabilized carbanions has also been described. In the second part of the review emphasis will be placed on the application of azido derivatives in organic synthesis. 1,3-Dipolar cycloaddition is an excellent tool in the construction of fivemembered heterocycles. Therefore, the formation of 1,2,3-triazoles from alkynes, enamines and 2-oxoalkylidenetriphenylphosphoranes will be discussed. Hence, the azido group is easily converted into amine, and phosphorus-containing azides can be considered to be azide-masked equivalents of amino derivatives or their N-protected derivatives. The application of such azides in the synthesis of phosphorus analogs of amino acids will be discussed. The synthesis of carbodiimides, imines, isothiocyanates and phosphonodipeptides has also been reviewed.