Phosphonyl oxides

Without additional reagents Phosphonylation with phosphonyl oxides... 

Pentavalent phosphorus derivatives can be converted to phosphonyl halides or phosphine oxides by partial hydrolysis or by other oxygen donors. 

Recently, Fossum et al. prepared several phosphine-oxide-containing monomers (Scheme 6.23).163 These monomers were used to prepare hyperbranched polymers in a typical aromatic nucleophilic substitution. However, only oligomers with M lower than 2500 g/mol were obtained. These results did not surprise us, since our previous work demonstrated that the para-hydroxyl group of the phosphonyl group is not very reactive and would require higher reaction temperatures.11... 

Romakhin et al. [49] showed that anodically generated phosphoniumyl radicals can add onto alkenes to yield phosphonylated alkenes through an anodic oxi-dation/addition/anodic oxidation/elimination/nucleophilic attack sequence (Scheme 17). 

The synthesis in Scheme 13.64 was carried out by E. Carreira and co-workers at ETH in Zurich, Switzerland. A key step in the synthesis in Scheme 13.64 is a stereoselective cycloaddition using a phosphonyl-substituted nitrile oxide, which was used to form the C(16)-C(17) bond and install the C(15) oxygen. 

Support-bound, enantiomerically pure alcohols can be converted into phosphonates by Mitsunobu esterification, which results in complete inversion at the stereo-genic center. This strategy has been used to prepare peptidyl phosphonates on solid phase. These are interesting transition-state analogs with potential utility as peptidase inhibitors (Figure 11.3 [12,13]) or tyrosine phosphatase inhibitors [14]. Serine or threonine derivatives can be converted into phosphonates by direct phosphonylation with an activated monoalkyl phosphonate [15] or by treatment with phosphonamidites RP(OR)NR2 in the presence of tetrazole followed by oxidation [16]. 

IR spectroscopy can be used to characterise not only different rubbers, but also to understand the structural changes due to the chemical modification of the rubbers. The chemical methods normally used to modify rubbers include hydrogenation, halogenation, hydrosilylation, phosphonylation and sulfonation. The effects of oxidation, weathering and radiation on the polymer structure can be studied with the help of infrared spectroscopy. Formation of ionic polymers and ionomeric polyblends behaving as thermoplastic elastomers can be followed by this method. Infrared spectroscopy in conjunction with other techniques is an important tool to characterise polymeric materials. 

Free radical cyclization of 1,6-diene (120) using diethyl phosphite or diphenylpho-sphine oxide initiated by peroxide, produces an organophosphorus compound (121) via the addition of a phosphonyl radical to an olefinic group (eq. 4.42a). Radical addition of PH3 to limonene (122) results in the formation of 4,8-dimethyl-2-phosphabicyclo[3.3.1]-nonane (123) (eq. 4.42b) [121, 122]. 

This chapter covers the main synthetically useful phosphonylation reactions, the corresponding processes of phosphinylation and tertiary phosphine oxide formation along with some related reactions. In all these reactions the phosphorus reactant (a phosphite, phosphonite, phosphinite, or derivative or tautomer thereof) is the nucleophilic component, herein these reactants are referred to collectively as phosphorus(III) reactants/acids, as appropriate in general these reagents are best used freshly distilled. Syntheses of phosphonates, phosphinates and tertiary phosphine oxides by nucleophilic substitution at phosphorus is not covered (for reviews of this area see Refs 6 and 16). 

Free radical promoted, cationic polymerization also occurs upon irradiation of pyridinium salts in the presence of acylphosphine oxides. But phosphonyl radicals formed are not oxidized even by much stronger oxidants such as iodonium ions as was demonstrated by laser flash photolysis studies [51, 52]. The electron donor radical generating process involves either hydrogen abstraction or the addition of phosphorus centered or benzoyl radicals to vinyl ether monomers [53]. Typical reactions for the photoinitiated cationic polymerization of butyl vinyl ether by using acylphosphine oxide-pyridinium salt combination are shown in Scheme 10. 

Michaelis-Arbnzov Reaction Anionic Phosphonylation Michael Addition Cyclopropanation Heck Conpling Oxidation... 

Thermal and Anionic Phosphonylation Phosphonomethylation Michael Addition Electrophilic Snbstitntion Heck Conpling Diels-Alder Reactions Oxidation Ozonolysis... 

Oxidation provides a general and efficient route to phosphonylated aldehydes. For example, dietliyl... 

Phosphonylation of a -3-(9-isopropylidene-a -pyridoxyl chloride via a Michaelis-Becker reaction, followed by deprotection with 1 M HCl and oxidation of the resulting primary alcohol with MnOj, produces diethyl (4-fonnyl-3-hydroxy-2-methyl-5-pyridyl)methylphosphonate (Scheme 5.38), an analogue of pyridoxal 5 -phosphate whose 5-position side chain has been replaced by a phospho-nomethyl group. The alcohol oxidation step can be accomplished with a wide range of reagents, such as activated MnOj in CHCI3 at room temperature (53%), PCC in CH2CI2 (83-86%), or the Swem reaction (>95%). ... 

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