Zita Rádai

To date the greenest method for the preparation of α-hydroxyphosphonates from substituted benzaldehydes and dialkyl phosphites

Abstract 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 n-pentane and crystallization on cooling.

Derivatization of phosphinic acids in the presence of ionic liquids

GRAPHICAL ABSTRACT ABSTRACT Phosphinic acids practically do not undergo direct esterification and other related derivatizations. To our surprise, phosphinic acids could be converted to phosphinates, thiophosphinates and phosphinic amides by reaction with alcohols, thioalcohols and primary amines, respectively, under microwave (MW) irradiation. Based on high level quantum chemical calculations, conclusions were drawn in respect of the scope and limitation of the MW technique. Moreover, the efficiency of the microwave-assisted direct derivatizations was highly enhanced by adding a catalytic amount of an ionic liquid to the reaction mixture prior to irradiation.

The synthesis and potential use of cyclic phosphinic acid derivatives

GRAPHICAL ABSTRACT Abstract Direct derivatizations, such as esterification and amidation of 1-hydroxy-3-methyl-3-phospholene oxide and subsequent transformations including ring enlargement of the phosphinates, and phosphorylation of the phosphinic amides so obtained are described.

Synthesis and Reactions of α-Hydroxyphosphonates

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.

Synthesis of α-hydroxyphosphonates and α-aminophosphonates

GRAPHICAL ABSTRACT ABSTRACT The Pudovik reaction between substituted benzaldehydes and dialkyl phosphites has been accomplished in a new, environmentally friendly way to afford the corresponding α-hydroxyphosphonates. During the substitution of α-hydroxyphosphonates by primary amines an unexpected neighboring group effect was found that promoted the formation of α-aminophosphonates. The phenomenon was justified by high-level quantum chemical calculations.