This review summarizes the main synthetic routes towards α-hydroxyphosphonates that are known as enzyme inhibitors, herbicides and antioxidants, moreover, a number of representatives express antibacterial or antifungal effect. Special attention is devoted to green chemical aspects. α-Hydroxyphosphonates are also versatile intermediates for other valuable derivatives. O-Alkylation and O-acylation are typical reactions to afford α-alkoxy-, or α-acyloxyphosphonates, respectively. The oxidation of hydroxyphosphonates leads to ketophosphonates. The hydroxy function at the α carbon atom of hydroxyphosphonates may be replaced by a halogen atom. α-Aminophosphonates formed in the nucleophilic substitution reaction of α-hydroxyphosphonates with primary or secondary amines are also potentially bioactive compounds. Another typical reaction is the base-catalyzed rearrangement of α-hydroxy-phosphonates to phosphates. Hydrolysis of the ester function of hydroxyphosphonates leads to the corresponding phosphonic acids.
The phospha-Brook rearrangement of dialkyl 1-aryl-1-hydroxymethylphosphonates
(HPs) to the corresponding benzyl phosphates (BPs) has been elaborated
under solid-liquid phase transfer catalytic conditions. The best procedure involved the use
of triethylbenzylammonium chloride as the catalyst and Cs2CO3 as the base in acetonitrile
as the solvent at room temperature. The substrate dependence of the rearrangement has
been studied, and the mechanism of the transformation under discussion was explored by
quantum chemical calculations. The key intermediate is an oxaphosphirane. The one-pot
version starting with the Pudovik reaction has also been developed. The conditions of this
tandem transformation were the same, as those for the one-step HP→BP conversion.
Recent synthetic methods for α-hydroxyphosphonates comprise a green, solvent-free accomplishment of the Pudovik reaction that was typically followed by extractions and recrystallization, or even by chromatography, or other operations. We now developed a general procedure applying 10% of triethylamine as the catalyst and a minimum quantity of acetone as the solvent, giving the products in a pure form after a reflux of 5–120 min following the addition of some
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