Phosphonic acids, from phosphorus

Figure 2.5 Direct synthesis of a phosphonic acid from white phosphorus.

Preparation of a-hydroxy-p-methylbenzylphosphonous acid — Preparation of a phosphonous acid from red phosphorus in aqueous medium23... 

Acidic and basic hydrolysis of GA result in different products (Fig. 4). Under acidic conditions, ethylphosphoryl cyanidate and dimethylamine are formed under basic and neutral conditions, ethyl A,A-dimethylamido phosphoric acid and hydrogen cyanide are formed. Although the latter pathway is predominant, di-methylphosphoramidate, phosphorocyanidate, and dimethylphosphoramide cyanidate may also be formed (Sanches et al. 1993). The phosphorus-containing compounds are slowly hydrolyzed to phosphoric acid. Although theoretically possible, there is little likelihood of formation of a detectable amount of methyl phosphonic acid from GA. Hydrolysis products are listed in Table 37. 

Surfactants are prepared which contain carboxylic acid ester or amide chains and terminal acid groups selected from phosphoric acid, carboxymethyl, sulfuric acid, sulfonic acid, and phosphonic acid. These surfactants can be obtained by reaction of phosphoric acid or phosphorus pentoxide with polyhydroxystearic acid or polycaprolactone at 180-190°C under an inert gas. They are useful as polymerization catalysts and as dispersing agents for fuel, diesel, and paraffin oils [69]. 

Use of a free flame instead of a heating bath to distil acetyl chloride produced from acetic acid and phosphorus trichloride caused the residual phosphonic ( phosphorous ) acid to decompose violently to give spontaneously flammable phosphine... 

Analysis of the Murchison meteorite led to a completely different type of phosphorus compound the only phosphorus-containing compounds found were alkanephos-phonic acids. Spurred on by these results, de Graaf et al. (1995) irradiated mixtures of o-phosphorous acid in the presence of formaldehyde, primary alcohols or acetone with UV light (low pressure Hg lamp, 254 nm with a 185-nm component) and obtained phosphonic acids, including hydroxymethyl and hydroxyethyl phosphonic acids, which had been found in the Murchison meteorite. Alkanephosphonic acids can be derived from phosphorous acid, with a P-H bond being replaced by a P-C bond. 

In the second instance, two approaches seem to be worthy of special note. The synthetic utility of elemental phosphorus based on it acting as a radical trap appears to be quite valuable, but additional effort is required to determine the variability of the source of the organic free radicals. (Is there some other, more efficacious, source of organic free radicals that works better with this system than acylated iV-hydroxy-2-pyridones ) The other approach that appears ripe for development is the hydrolysis/elimination with "phosphorates" derived from the oxidative addition of white phosphorus to alkenes. We look forward to the continued development of such facile approaches toward the preparation of fundamental phosphonic acids. 

Hoerold, S., Weferling, N., and Breuer, H.-R, Preparation of phosphonic acid esters from alkyl halides and elemental phosphorus, and their use, Ger. DE 19,828,861, 2 Dec. 1999 Chem. Abstr., 132, 12410r, 2000. 

A sample of phosphonic acid resin Diaion CRP200 in wet Na+ form was kindly provided from Mitsubishi Chemical Co. Ltd. This wet resin sample was dried in vacuum, and then the resin with particle sizes of 60 - 32 mesh was selected by meshing. The selected resin was conditioned by treatment with 1 M HC1, water, 2 M NaOH, water, 1 M HC1, and water in successive. Finally, thus, the resin was changed into H+ form. The phosphorus content and acid capacity of the selected resin in the H+ form were measured according to the reported methods and were 4.6 mmol/g and 8.8 meq/g, respectively. Wet volume of the resin was 2.6 ml/g. Hereafter, this is abbreviated as CRP200 for simplicity. 

Phosphonic acid esters are derived from phosphonic acid (often erroneously called phosphorous acid), which is shown with some of its esters in Figure 18.3 Only two of the H atoms of phosphonic acid are ionizable, and hydrocarbon groups may be substituted for these atoms to give phosphonic acid esters. It is also possible to have esters in which a hydrocarbon moiety is substituted for the H atom that is bonded directly to the phosphorus atom. An example of such a compound is dimethylmethylphosphonate, shown in Figure 18.3. This type of compound has the same elemental formula as triesters of the hypothetical acid P(OH)3, phosphorous acid. Examples of triesters of phosphorous acid, such as trimethylphosphite, are shown in Figure 18.3. 

Another important source of chiral auxiliaries for the synthesis of optically active phosphorus derivates are the C2 symmetric diamines such as 1,2-diaminocyclohex-anes. In 1994, Hanessian and co-workers described the use of A,/V -dimethyl-(R,R)-1,2-diaminocyclohexane 93 as a chiral auxiliary in the synthesis of optically pure or enantiomerically enriched a-alkyl a-amino phosphonic acids [49], Starting from easily accessible optically pure diamine 93, they synthesized in good yield (75 %) enantiomerically pure (R,R)-ethylphosphonamide 94 by condensation with ethyl phosphonic dichloride in benzene in the presence of triethylamine (Scheme 43). 

The primary addition product from HFA and diphenylphosphane (32b) has been unambiguously characterized by several groups (97, 755). It is easily oxidized by atmospheric oxygen and dinitrogen tetroxide (97, 755) to form phosphonous acid ester 33b via phosphane oxide 36 (755), which can also be synthesized from HFA and diphenylphosphane oxide. Kinetics of the base-catalyzed rearrangement have been studied (754). Further action of HFA on 32b yields difluorophosphorane 37 (755). A dipolar intermediate with tetra-coordinated phosphorus has been postulated by Stockel (260) in the formation of 33b and 33c (R = c-CgHu). 

---