Polymer-supported phosphonate

Polymer-supported Wittig reagents have recently been developed as an extension to the traditional reagents.29 For example, polystyryldiphenylphosphine has been developed in an attempt to replace the use of triphenylphosphine in the preparation of phosphoranes (see Protocol 1). The hope is that these polymer-bound regents will overcome the practical problem of removing the triphenylphosphine oxide by-product formed in Wittig reactions. Polymer supported phosphonates and Wittig substrates have also been prepared for use in solid phase synthesis and combinatorial chemistry.30... 

Dioxolans 146 can be considered as masked carbonyl functionalities, and are cleaved under acidic conditions. In solution, the olefination of a dioxolan-protected ketone would therefore be a two-step transformation consisting of deprotection and olefination. Using polymer-supported adds, e.g., strongly addic Amberlyst resin 147 and polymer-supported phosphonates 135 (Scheme 25), the two-step transformation involving the carbonyl compound 137 as intermediate could be performed simultaneously in one pot (Scheme 27) [113]. The product 136 was isolated by filtration. This procedure would not work as a one-pot sequence in solution because the acidic catalyst would immediately quench the basic phospho-nate resin. 

Higher pH chromate programs (pH 7.0 to 9.0), using chromate (3 to 15 ppm) with P04 (3 to 6 ppm) and/or Zn (0.5 to 2.5 ppm). Phosphonate/polymer support is required, the selection of which permits progressively lower chrome levels and higher cooling water pH. 

Polymer-supported peracids are also used effectively for the epoxidation of di-and trisubstituted olefins. The ratio of the stereoisomers is similar to that for the products of the reaction of the monomer with aromatic peracids. MCPBA epoxidation of homoallyl phosphonates has led to the preparation of 3,4-epoxyalkane phosphonates 39 in addition to the 1,2- and 2,3-epoxy derivatives.Stereospecific peracid oxidation is one of the preparative methods employed in the synthesis of the structurally varied cyclic polyoxirane isomers, which are of interest from a biological aspect. ... 

Scheme 19.2 Methods for polymer-supported oligonucleotide synthesis. Dinudeoside phosphate formation in the common methods for oligonucleotide synthesis phosphodiester (I), phosphotriester (II), phosphite triester (III) and H-phosphonate (IV).

In the present paper, we examine the influence of structural variation within series of crown ether carboxylic acid and crown ether phosphonic acid monoalkyl ester carriers upon the selectivity and efficiency of alkali metal transport across three types of liquid organic membranes. Structural variations within the carriers include the polyether ring size, the lipophilic group attachment site and the basicity of ethereal oxygens. The three membrane types are bulk liquid membranes, liquid surfactant (emulsion) membranes and polymer-supported liquid membranes. 

Crown ethers have been immobilized within polymer supports and used in metal ion separation, Crown ether moieties at cross-linked polystyrene have been prepared by the reaction of cross-linked chloromethylated polystyrene with hydroxyl-substituted crown ethers [52], The resins 15 formed from the condensation of dibenzo—18-crown-6 and formaldehyde were modified with phosphonate monoethylester and phosphonic acid groups [53]. Resin 15 demonstrates selectivity for K(I) over the other alkali metal ions at pH < 8, and selectivity for Li(I) at pH > 8. A resin 16 prepared from the condensation of a substituted crown ether with formaldehyde is selective for Na(I) over the other alkali metal ions [54],... 

Finally, the palladium-catalyzed cross-coupling reactions with supported enol phos-phonates were reported by Steel and coworkers (Table 1.13, Entry 1) Polymer-supported lactam enol phosphonates were prepared and multifunctional cleavage was demonstrated, using Suzuki conditions, to provide aryl enamines in good yields. 

The formation of flve-membered cyclic imines through a Staudinger/intramolecular aza-Wittig reaction can also be performed by solid-phase synthesis and has been applied for the first synthesis of lanopylin Bi (108). The total synthesis, which takes only four steps, starts with a phase-transfer alkylation of diethyl 2-oxopropylphosphonate 105 with a 2-iodoethyl azide, affording the azido phosphonate 106, which undergoes a phase-transfer Homer-Emmons Wittig reaction with heptadecanal to provide the azido enone 107. An intramolecular aza-Wittig reaction of the enone 107 with polymer-supported triphenylphosphine in toluene completed the first total synthesis of lanopylin Bi (108) in 76% yield (Scheme 15.22). 

ROMP polymers bearing acid chloride, phosphonate, carbodiimide, phosphonyl chloride, and phosphine groups have been used as platforms in phase-switching, sequestration, capture-release, and soluble support applications. 

Functionalized polymers are of interest in a variety of applications including but not limited to fire retardants, selective sorption resins, chromatography media, controlled release devices and phase transfer catalysts. This research has been conducted in an effort to functionalize a polymer with a variety of different reactive sites for use in membrane applications. These membranes are to be used for the specific separation and removal of metal ions of interest. A porous support was used to obtain membranes of a specified thickness with the desired mechanical stability. The monomer employed in this study was vinylbenzyl chloride, and it was lightly crosslinked with divinylbenzene in a photopolymerization. Specific ligands incorporated into the membrane film include dimethyl phosphonate esters, isopropyl phosphonate esters, phosphonic acid, and triethyl ammonium chloride groups. Most of the functionalization reactions were conducted with the solid membrane and liquid reactants, however, the vinylbenzyl chloride monomer was transformed to vinylbenzyl triethyl ammonium chloride prior to polymerization in some cases. The reaction conditions and analysis tools for uniformly derivatizing the crosslinked vinylbenzyl chloride / divinyl benzene films are presented in detail. 

---