Phosphonates oxidation

Much effort has been placed in the synthesis of compounds possessing a chiral center at the phosphoms atom, particularly three- and four-coordinate compounds such as tertiary phosphines, phosphine oxides, phosphonates, phosphinates, and phosphate esters (11). Some enantiomers are known to exhibit a variety of biological activities and are therefore of interest Oas agricultural chemicals, pharmaceuticals (qv), etc. Homochiral bisphosphines are commonly used in catalytic asymmetric syntheses providing good enantioselectivities (see also Nucleic acids). Excellent reviews of low coordinate (coordination numbers 1 and 2) phosphoms compounds are available (12). 

Addition of Metalated Allylic Phosphine Oxides, Phosphonates, Sulfones, and Sulfoxides and Sulfoximines to a,/i-l nsaturated Carbonyl Compounds... 

In contrast to allylic phosphine oxides, phosphonates, sulfones and sulfoxides, the chemistry of lithiated allylic sulfoximines has been less extensively developed25 27. The reaction of lithiated racemic A-phenyl-A -(4-rnethylphenyl)-S -(2-propenyl)sulfoximine with either 2-cy-clopentenone or 2-cyclohexenone gave a complicated mixture with 1,4-oc-ad ducts being slightly favored over the 1,4-7-adducts. The yields of these adducts were poor25. In contrast, lithiated racemic Ar-tert-butyldiphenylsilyl-5-phenyl-5,-(2-propenyl)sulfoximine gives mainly 1,4-y-ad-ducts on reaction with the same enones26. 

Table 8.3. Properties of metal oxide phosphonic acid cements (Ellis, 1989 Ellis Wilson, 1991)...

This implies that the selective layer of reverse osmosis membranes may have a different origin from that of the micelles. Such a case is clearly identified by examination of the skin structure of cellulose acetate/poly(bromophenylene oxide phosphonate) alloy membranes (1 ), which exhibit a high flux and high salt separation (Figure 13). The skin rests on an assembly of giant spheres (up to 1 pm in diameter) and is certainly originated by a different coagulation mechanism than that of the spheres. 

Figure 13. Cross-section of the skin zone of a reverse osmosis membrane consisting of cellulose acetate-polyfbromophenylene oxide phosphonate)...

Oxygen was abstracted from phosphine oxides, phosphonates,407 arsine oxides and sulfoxides by MX5 as well as by [MX4Me] (X = C1, Br),408 and more easily by the Nb than by the Ta derivatives, to yield MOX3 adducts (equation 36 Table 21). IR indicated the following sequence for the metal s acceptor character MCI5 > MOCl3 > MOCl2Me. NMR showed that in... 

S. G. Pyne, Addition of Metalated Allylic Phosphine Oxides, Phosphonates, Sulfones, Sulfoxides and Sulfoximines to a,/3-Unsaturated Carbonyl Compounds , in Stereoselective Synthesis (Houben-Weyl) 4th ed. 1996, (G. Helmchen, R. W. Hoffmann, J. Mulzer, E. Schaumann, Eds.), 1996, Vol. E21 (Workbench Edition), 4, 2068-2086, Georg Thieme Verlag, Stuttgart. 

In contrast to stabilizers, fire retardants must be added in much higher concentrations, which affect thermal and mechanical properties as well as cost. Sherr and co-workers report that novel derivatives of phosphine oxides, phosphonic acids, phosphinic acid, and phosphonium halides may be used generally in concentrations as low as 2.5-5 p.p.h. to be effective fire retardants in polyethylene and poly (methyl methacrylate). 

Phosphine Oxides, Phosphonic Acids, and Phosphinic Acids... 

Phosphine oxides, phosphonic acids, and phosphinic acids have been found to be flame retardants for various thermoplastic polymers. While there are many reasons for their effectiveness, we postulate that the acidity of the compounds is directly related to their activity and that the formation of polyphosphates (or phosphate glasses) is vital to the mechanism by which they function. 

In this paper we report the use of some phosphine oxides, phosphonic acids, and phosphinic acids to impart fire retardant properties to polymers. In addition, we postulate a mechanism by which these compounds behave as flame retardant agents. 

Tn the preceding chapter (19) we described the use of phosphine A oxides, phosphonic acids, and phosphinic acids as flame retardants for thermoplastic materials. We also have found phosphonium halides to be effective flame retardants for plastics (5, 6). These compounds were either the monophosphonium halides,... 

SYNS C.I. 77620 DIBASIC LEAD METAPHOSPHATE DIBASIC LEAD PHOSPHITE LEAD OXIDE PHOSPHONATE, HEMIHYDRATE LEAD PHOSPHITE, dibasic (DOT)... 

Asymmetric Wittig-Homer reactions Wittig-Horncr reactions have usually involved phosphine oxides, phosphonates, or phosphonamidcs. Highly enantioselcctivc ole-finations have now been achieved by use of this chiral phosphonamidatc 1. Thus the anion (t-BuLi) reacts with 4-/-butylcyclohexane to form 2 in >98% de. Elimination with trityl triflate/2,6-lutidine provides the alkylidene 3 with essentially complete stercospccificity. The reaction was shown to be applicable to a variety of 4-alkylcyclohexanones. 

Dibasic lead phosphite EINECS 235-252-2 Halphos Lead oxide phosphite Lead oxide phosphonate (Pb302(HP03)) Trilead dioxide phosphonate, A heat/light stabilizer used with PVC. Halstab. 

The oxidative phosphonation of the 4-chloroalk-l-enes 94 (R = H or Me R = Bu or Ph) yields mixtures of the phosphonic dichlorides 95 and 96 together with the chloroalkyl... 

A similar synthetic sequence on the enantiomer 226S provided 227S. Oxidation, phosphonate formation [135], and acetal hydrolysis provided enone phosphonate 230. Condensation with the racemic dienal 231 yielded diastereomeric tetraenes 232, which corresponded to the C12-C25 fragment of pimaricin 54. 

Lead oxide phosphonate, hemihydrate. See Lead phosphite dibasic... 

Synonyms Cl 77620 Dibasic lead metaposphate Dibasic lead phosphite Lead oxide phosphonate, hemihydrate Definition Avail, commercially as the hemihydrate Empirical HOsPPbs Formula 2PbO PbHPOj Y2H20... 

Lead oxide brown. See Lead dioxide Lead oxide phosphonate, hemihydrate. See Lead phosphite dibasic Lead oxide, red CAS 1314-41-6 UN 2291 (DOT)... 

Stackman [29] carried out a study to find systems suitable for reducing the flammability of polyethylene terephthalate (PET) and poly-1,4-butylene terephthalate (PBT) while retaining the chemical and physical properties of the original polymers. The additives used were phosphine oxides, phosphonates and phosphates and their activity was assessed by means of an oxygen index test. Most of the phosphorus esters were found to be volatile under the blending conditions and both the halogenated phosphorus esters and halogenated derivatives of phosphorus oxide proved to be ineffective as flame retardants. 

An intriguing oxidative coupling of indoles with a-amino ketones can selectively afford a-aryl a-imino and a-aryl a-oxo carbonyl compounds under argon and air atmosphere, respectively (Scheme 2.8) [38]. The mechanistic studies demonstrated that stronger oxidizing conditions favored the hydrolysis process, and the traditional acidification hydrolysis is unlikely. Later, oxidative phosphonation and alkylation of a-amino ketones with diarylphosphine [39] and ethers [40] were reported. 

A direct oxidative phosphonation reaction of azoles with dialkyl phosphites in the presence of Pd(OAc)2 as the catalyst and oxone as the oxidant has been disclosed (eq 186). ... 

One of the first variations of the Wittig reaction was initially reported by Homer and coworkers and rapidly followed by an initial report by Wadsworth and Emmons. These examples made use of phosphine oxide/phosphonate derivatives of the ylides first reported by Wittig and are now collectively known as the Homer-Wadsworth-Emmons reaction (HWE). Ylide formation occurs upon deprotonation of dialkoxy phosphonate 31 and alkene 32 is formed from carbonyl compound 30 with loss of the corresponding phosphate derivative 33. The use of this variation has advantages over the eonventional version a) phosphonate carbanions are known to be more nucleophilic due to decreased stabilization by valence shell expansion of the phosphorous atom, thus are able to react with a wider diversity of carbonyl compounds, b) the phosphorous-based product of the reaction, a water-soluble phosphate, allows for a greater ease of reaction work-up. c) the enhanced reactivity of the phosphonate permits direct derivitization of the reagent, d) the Arbuzov reaction allows for ready preparation of the desired phosphonate. 

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