Transesterification phosphonous

This work has been extended to transesterification with secondary alcohols [23], and of phosphonate esters [24], Movassaghi and co-workers have demonstrated that NHCs effectively catalyse the amidation of esters with amino alcohols, although an alternative mechanism involving the NHC acting as a Brpnsted base, resulting in nucleophilic activation of the alcohol for an initial transesterification event, followed by rapid O- to iV-acyl transfer, has been proposed [25, 26],... 

Orthophosphoric and benzylphosphonic acids have been selectively alkylated with triethyl phosphite in a new synthesis of mono-, di-, and triethyl phosphates and of mono- and di-methyl phosphonates.62 A-Methylol carboxamides and sulphonamides react with trialkyl phosphites to give the phosphonate derivatives (78) and (80), respectively.63 However, the mechanism appears to be quite different in each case while the carboamides react by a transesterification-rearrange-ment pathway, the sulphonamides undergo elimination-addition via the imine (79). 

Nolan and co-workers have extended the scope of transesterification reactions to include phosphonate esters as phosphorylating agents [137]. In this publication the authors use dimethyl methylphosphonate 273 and benzyl alcohol with a variety of imidazolylidene carbenes (Table 23). The nse of molecnlar sieves to absorb methanol leads to increased conversion however, longer reaction times lead to decreased... 

Because of the possibility of racemization during the transesterification reaction (strong basic conditions) alternative methods are reported. These include transesterification in the presence of the KF/18-crown-6 ether 461 or the use of titanium tetraalkoxides. 471 The methods are efficient and represent a route to any required dialkyl ester using diphenyl esters as starting materials. Diphenyl groups can also be removed by hydrogenation in the presence of platinum dioxide (Adams catalyst) to provide the free phosphonic acid moiety directly)46 ... 

The main problem here is removing the phenyl ester groups from the phosphonic moiety.We have found that convenient routes for deblocking are hydrogenation on Adams catalyst and transesterification methods followed by hydrogen bromide in glacial acetic acid treatment. The best results ewre obtained if transesterification was carried out using potassium fluoride-crown ether-methanol system. 

Reichwein, J. F., Pagenkopf, B. L. New Mixed Phosphonate Esters by Transesterification of Pinacol Phosphonates and Their Use in Aldehyde and Ketone Coupling Reactions with Nonstabilized Phosphonates. J. Org. Chem. 2003, 68,1459-1463. 

Bromo- and iodotrimethylsilane, reagents compatible with alkyne and other functionalities, are suitable for the mild P-0 dealkylation of dialkyl 1-alkynylphosphonates to give the corresponding phosphonic acids.The greater reactivity of iodotrimethylsilane will probably prove advantageous for the low-temperature dealkylation of phosphonates having triple bonds. However, transesterification of diethyl 2-propynylphosphonate with iodotrimethylsilane at -30°C followed by solvolysis with MeOH led quantitatively to the 1-propynylphosphonic icid. ... 

Berte-Verrando, S., Diziere, R., Samadi, M., and Savignac, P, New route to aminopHjlmethylphosphonic acid via i>w(trifluoroethyl) phosphonate transesterification, J. Chem. Soc., Perkin Trans. 1, 3125, 1995. 

Several reports show that it is possible to carry out a transesterification selectively at the carboxylic ester moiety of dialkyl l-(alkoxycarbonyl)methyIphosphonates rather than at the phosphonic ester moiety with primary and secondary alcohols in the presence of NaH or DMAPP For example, a number of chiral phosphonates have been prepared in high yields (80-96%) by DMAP-catalyzed transesterification of dialkyl l-(alkoxycarbonyl)methylphospho-nates with 8-phenytmenthol in toluene at reflux." " -" ... 

A new method for intemucleotide bond formation uses a transesterification reaction in pyridine of the aryl nucleoside /f-phosphonate diesters (76) with a... 

Masked ionomeric groups may also be used. They generate ions during melt processing. Examples include phosphonate esters that form phosphonic acid salt in the melt by transesterification with a salt, e.g., zinc stearate. 

The transesterification reactions in PBT/PC melt blends could be suppressed by using organo-phosphites and phosphonates which probably function by deactivating the titanium or antimony type polymerization catalyst residues present in PBT [Golovoy et al., 1989]. Even in the presence of phosphite stabilizers, PBT/PC blends showed dual phase behavior. However, a partial miscibility was evident since the T of PC phase was still reduced from the normal 150°C to about 140°C. This partial miscibility between PBT and PC which occurs even in the absence of an exchange reaction is responsible for the good compatibility and interfacial strength of the blend. 

When NaOMe was employed as catalyst in the initial reaction, the formation of 262 was accompanied by that of significant amounts of the 3-hydroxy-l,2-oxaphosph(V)olanes 263, again as mixtures of diastereoisomers. The latter are also obtained through the tri-ethylamine-catalysed intramolecular transesterification of the linear esters 262 Mixtures of linear and cyclic acylated phosphonic esters, e.g. the acetates of 262 and 263, result when 4-acetyloxybutan-2-one is acted upon by a dialkyl hydrogenphosphonate". ... 

Conventional organic synthesis procedures are sometimes employed to prepare the simpler types of those molecules included here. Thus, (v/c-dihydroxyalkyl)phosphonic diesters are obtainable through the hydroxylation of the corresponding unsaturated acid esters using OSO4 and standard techniques. The isolation and purification of a diol may prove to be difficult because of possible intramolecular transesterification, sometimes accompanied by dehydration (reaction 12)" ... 

The factors affecting the competition between transesterification and olefination in reactions of phosphonoalkylcarboxylates (111) with aldehydes and potassium carbonate in alcohols under heterogeneous conditions have been investigated.57 The reaction of the carbanion of I-cyano-1-fluoromethanephosphonate, prepared in situ from diethyl cyanomethane-phosphonate (112) and N-fluorobis(trifluoromethanesulphonyl)imide, with aldehydes and ketones provides a synthesis of a-fluoro-a,3-unsaturated nitriles (113) in moderate yield (Scheme 8).5 Wadsworth-Emmons... 

A second example involves a transesterification reaction catalyzed by an antibody generated against a phosphonate diester transition state analogue [11]. The antibody catalyzes the corresponding acyl transfer reaction of thymidine and an alanyl ester with an effective molarity of 3 x 10 m... 

Fig. 3 (A) [33] Sigrnatropic rearrangement of chorismate to prephenate catalyzed by antibody 11F1-2E11. The hapten is a shape mimic of the cyclic transition state. (B) Antibody 1E9 catalyzes a Diels-Alder reaction of tetrachlorothiophene dioxide and yV-ethylmaleimide. The hapten is comprised of the endo hexachloronorbornene unit. (C) Antibody 21H3A catalyzes the transesterification reaction between iec-phenethyl alcohol and an enolic ester to form a chiral ester. The hapten here is racemic phosphonate.

The tritiated benzophenone-containing derivative of glucose 6-phosphate 23 was made as a photoactivatible affinity label for proteins. Phosphonate 24 was prepared to act as a hapten to elicit monoclonal antibodies for transesterification reactions between 25 (R = H) and 26 however, the antibodies failed to catalyse the reaction. D-Galactose 6-0-phosphate and 0-thionophosphate monoesters 27 have been prepared and then deacetalated by heating in water without added acid. ... 

Chem. Descrip. Triphenyl phosphite CAS 101-02-0 EINECS/ELINCS 202-908-4 Uses Costabilizer for PVC and other polymers such as PP vise, modifier, reactive diluent for a variety of resin systems, esp. epoxies antioxidant for syn. rubbers, butyrates flame retardant for PU foams in transesterification reactions lubricant oil additive chem. intermediate for prod, of other phosphite esters and phosphonates Features Improves adhesion, elec, props., dimensional stability Properties Colorless mobile liq. 10% P Albrite Tributyl Phosphate [Huntsman Surf. Sciences]... 

The synthesis of higher dialkyl H-phosphonate homologues usually includes the initial treatment of phosphoms trichloride with methyl alcohol, and then the transesterification of so-formed dimethyl H-phosphonate with higher alcohols [16,17],... 

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