Organophosphorus additive phosphonates

ORGANOPHOSPHORUS ADDITIVE FLAME RETARDANTS 5.4.1 Phosphates and Phosphonates... 

In addition to phosphonium salts, which are widely used for the activation of urethane-protected amino acids in peptide synthesis (see Section 3.7), other organophosphorus reagents derived from phosphinic, phosphonic, and phosphoric adds have proved to be efficient coupling reagents. 

Dialkyl phosphites react slowly with epoxy ketones at room temperature in the presence of a catalytic amount of sodium metal to form dialkyl l-hydroxy-2,3-epoxypropylphosphonates in 41-99% yields.Similarly, dialkyl phosphites react with f7.v-]-fonnyl-l-trimethylsilyl-l,2-cpoxy-alkanes in the presence of DBU in THF to give dialkyl ] -hydroxy-2-trirnethylsilyl-2,3-epoxy ilkyl-phosphonate in high yields (84%, Scheme 4.16).By contrast, DBU or EtjN in C,H, at reflux was found inefficient for the addition of dimethyl phosphite to the epoxide derived from chalcone. The reaction is best carried out in the presence of KF2H2O to produce a diastereomeric mixture of hydroxyphosphonates free from other organophosphorus compounds. 

As extractants of polyvalent metal ions from acidic solutions, these reagents have one additional limitation they are also moderately efficient extractants for mineral acids. As the neutral organophosphorus compound extracts the free acid, the free-extractant concentration in the counter-phase is reduced, and metal-ion extraction efficiency suffers. To overcome this limitation, considerable effort has been expended in recent years to evaluate the ability of carbamoylphosphonates (CPs,(RO)2 PO(CO)N(R )2), carbamoylmethyl phosphonates (CMPs (RO)2POCH2(CO)N(R )2), and carbamoylmethylphosphine oxides (CMPOs, R2POCH2(CO)N(R )2) to extract lanthanide and actinide metal ions. These extractants are referred to collectively as bifunctional extractants. The first report of these ligands were made by Siddall (1963,1964). 

The synthetic potential of the obtained phosphonates has been demonstrated in electron-deficient iminophosphonates by their easy functionalisation to afford various acyclic and heterocyclic derivatives with an aminophosphonic fragment by the use of reductive nucleophilic addition reactions, direct aminoallg lation of electron-rich heterocycles, cyclocondensations, and dipolar cycloaddition reactions. In the subsubsection devoted to reactions of phosphonates, ketophosphonates, vinylphosphonates, alkinylphosphonates, vinyl- and vinylidenebisphos-phonates were widely used as organophosphorus reagents. 

The chapter on quinquevalent phosphorus acids and their derivatives continues to be an area of interest. It shows some of the most important achievements in the area of organophosphorus compounds containing three P-O bonds (phosphates), two P-O and one P-C bonds (phosphonates) as well as one P-O and two P-C bonds (phosphinates), in addition... 

Kharasch MS, Mosher RA, Bengelsdorf IS (1960) Organophosphorus chemistry addition reactions of diethyl phosphonate and the oxidation of triethyl phosphite. J Org Chem 25 1000-1006... 

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