Sulfonyl polymer supported

A catch and release synthesis of tetrazoles and cyclic amidines has been reported making use of solid-supported oximes [94]. When bound sulpho-nyloximes, obtained by reacting polymer supported sulfonyl chloride with oximes, were reacted with nucleophiles, tetrazoles or cychc amidines were obtained (Scheme 19). Alternatively, the use of TMS-CN affords imino nitriles, which have been used as intermediates for the preparation of indoles, 1,2,3,4-tetrahydropyridines, quinoxalines and benzimidazoles. 

Polymer-supported sulfonyl chloride 14 as a capture-release resin. 

Oxetanes have also been synthesized by the immobilization of 2,2 -disubstituted 1,3-diols with polymer-bound sulfonyl chloride, followed by intramolecular cyclization/cleavage from the solid support (Scheme 17) <2005TL643>. One percent divinylbenzene (DVB) cross-linked polystyrene and polyethylene glycol (PEG) (average Mn 3400) were used as polymer support in this reaction, and in both cases the properties of the polymer support allowed rapid purification of the intermediate. Intermediates on the insoluble cross-linked polystyrene support could be washed with a range of organic solvents to remove insoluble impurities, whereas the soluble PEG supported products could be purified by recrystallization from isopropanol. This is thought to represent the first reported polymer-supported synthesis of oxetanes. 

In recent years, catalytic asymmetric Mukaiyama aldol reactions have emerged as one of the most important C—C bond-forming reactions [35]. Among the various types of chiral Lewis acid catalysts used for the Mukaiyama aldol reactions, chirally modified boron derived from N-sulfonyl-fS)-tryptophan was effective for the reaction between aldehyde and silyl enol ether [36, 37]. By using polymer-supported N-sulfonyl-fS)-tryptophan synthesized by polymerization of the chiral monomer, the polymeric version of Yamamoto s oxazaborohdinone catalyst was prepared by treatment with 3,5-bis(trifluoromethyl)phenyl boron dichloride ]38]. The polymeric chiral Lewis acid catalyst 55 worked well in the asymmetric aldol reaction of benzaldehyde with silyl enol ether derived from acetophenone to give [i-hydroxyketone with up to 95% ee, as shown in Scheme 3.16. In addition to the Mukaiyama aldol reaction, a Mannich-type reaction and an allylation reaction of imine 58 were also asymmetrically catalyzed by the same polymeric catalyst ]38]. 

These were further sulfonylated using polymer-supported sulfonylpyridinium ion 156 to give sulfonamides 157 [121],... 

Polymer-supported sulfonyl chlorides can be used for the selective monosulfonyl-ation of anilines, as demonstrated by the Ley group [71, 72], Commercially available polystyrene-DMAP (4-dimethylaminopyridine) was treated with different aryl sulfonyl chlorides to form polymer-bound sulfonylation reagents. These were reacted with substituted anilines to form an array of hydroxamic acids (Scheme 6.17), using a synthetic strategy involving polymer-bound reagents in all steps. The products were subsequently evaluated as histone deacetylase inhibitors. 

Obviously, the incorporation of an electron-withdrawing substituent in the polymer-supported benzotriazole ring should enhance its reactivity. Thus, the sulfonamide-substituted HOBt resin 34 (Section 7.3) has been obtained by reaction of aminomethylated divinylbenzene cross-linked polystyrene with the sulfonyl chloride 116 to give supported sulfonamide 117, followed by typical hydroxybenzo-triazole formation (Scheme 7.37) [128]. The effect induced by the sulfonamide group was determined by measuring the acidity of non-polymeric analogues, showing a pKa of 3.59 for the sulfonamide-substituted HOBt, and a pKa of 4.64... 

Reagents of by-products can also be trapped by covalent binding to a polymer. Kaldor et reported the use of aminomethyl polystyrene for the extraction of isocyanates, acid chlorides or sulfonyl chlorides from reaction mixtures (Scheme 3.4.3, entry a). Similarly, amines were trapped with polymer-supported isocyanates, acid chlorides or aldehydes (Scheme 3.4.3, entry b). 

The field of organic chemistry has seen the most extensive use of polymeric materials as aids in effecting chemical transformation and product isolation. Insoluble polymer supports have been used as handles to facilitate these functions. As chemical reagents can be bound to an insoluble polymer carrier and used in organic synthesis [117,118], polymer-bound reagents can also be used to assist in the purification step of solution-phase reactions [119,120]. The latter are known as scavenger resins. These are added to the reaction mixture upon completion of the reaction in order to quench and selectively bind to the unreacted reagents or by-products. The polymer-bound impurities are then removed firom the product by simple filtration to obtain pure compounds. For example, aminomethylated poly(styrene-co-divinyl benzene) can be used to remove acid chlorides, sulfonyl chlorides, isocyanates, thiocyanates, and proton. Similarly, 2-Chlorotrityl resins have been developed for the attachment of carboxylic acids, alcohols. 

Itsimo [25] has also shown that polymer-supported OPEN monosulfonamides containing sulfonated pendent group (Scheme 16) are able to catalyze the HTR reduction of ketones in water with sodium formiate as hydrogen donor (S/C = 100). However, TsDPEN immobilized on polystyrene crosslinked or not, polymer 30 and 31 respectively, shrank in water. Sodium /j-styrene sulfonate was copolymerized with chiral A-(vinylbenzene-p-sulfonyl)-DPEN (20) imder radical polymerization conditions with or without DVB leading respectively to ligand 32 and 33. Control of the balance hydrophilicity/hydrophobieity of the polymer support is carried out by changing the salt from Na to quaternary ammonium. All of these polymers swelled in water, and their respective ruthenium, rhodium or iridium complexes were prepared. Compared to sodium salt polymer-supported catalyst from 32a and 33a, ammonium... 

More recently, several polymer versions of the efficient Corey-Bakshi-Shibata (CBS) catalyst have been prepared [47], Different approaches have been used to bind the catalytic moieties to the polymer support the diphenyl prolinol reacted with beads bearing benzene sulfonyl chloride residues (catalytic moieties boimd to the nitrogen atom as part of a sulphonamide link), the diphenyl prolinol is boimd to a polymer support or the aminoalcohol... 

Itsuno has described the first enantioselective allylation of aldehydes using crosslinked polymer-supported A-sulfonylated aminoalcohols as chiral ligands [146], Polymer-supported ligands 220 and 221 were prepared by copolymerisation of the norephedrine-derived monomer 218 or D-camphor-derived 219 with styrene and divinylbenzene (DVB) in a [chiral monomer]/[styrene]/[DVB] molar ratio of 1/8/1 (Scheme 90). 

Polymer-supported Reagents. Polymer-supported toluene-sulfonyl azide I3I was prepared by reaction of a macroreticular p-toluenesulfonyl chloride resin (prepared, in turn, by chlorosul-fonation of Amberlite XE 305) with excess sodium azide. Resin 13, a solid-phase equivalent of />-toluenesulfonyl azide, can be used for diazo transfer to /3-dicarbonyl compounds (eq 14). Unlike tosyl azide, resin 13 does not detonate on shock treatment and is stable at room temperature. Recently, an analogous benzenesul-fonyl azide resin has been prepared from PS-TsCl. ... 

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