Oximes polymer-bound

Imanaka—heterogenization of Rh complexes. In 1991, Imanaka and coworkers124 reported the heterogenization of Rh complexes by binding them to aminated polymers. As discussed previously, these findings led to fruitful research by Ford, Pardey, and others. The isolated polymer-bound Rh carbonyl anion complex was found to be reusable for reactions such as water-gas shift and reduction of nitro compounds. The polymer-bound Rh complexes were characterized by infrared spectroscopy. Water-gas shift activity (80 mol H2 per mol Rh6(CO)i6 in 24 hours) was recorded using the Rh complexes at 100 °C with 0.92 atm of CO, 2.16 ml H20, 0.05 mmol Rh6(CO)16, aminated polystyrene, 5.0 mmol of N, 5.56 ml ethoxyethanol and reduction of nitro-compounds (e.g., aliphatic nitro compounds to nitriles, oximes to nitriles, hydroxylamines to nitriles, and N-oxides to amines) occurred at 40 °C. 

The nucleophilic reactivity of the polymer-bound oximates and hydroxamates [25]—[28] is significantly enhanced (Kirsh et al., 1974, 1975 Okahata and Kunitake, 1977). Although the rate acceleration in these systems (10-100-fold) is relatively small compared with that in micellar systems, it is interesting to... 

WF DeGrado, ET Kaiser. Polymer-bound oxime esters as supports for solid-phase peptide synthesis. Preparation of protected fragments. J Org Chem 45, 1295, 1980. 

Nakagawa, ET Kaiser. Synthesis of protected peptide segments and their assembly on a polymer-bound oxime application to the synthesis of a peptide model for plasma apolipoprotein A-I. J Org Chem 48, 678, 1983. 

F. Polymer-bound Oximes in Solid-phase Synthesis. 182... 

The polymer-bound p-nitrobenzophenone oxime (71d) has been found to be a suitable support for stepwise peptide synthesis. Protected peptides can be assembled on 70d by coupling and deprotection steps similar to those employed in the usual Merrifield solid-phase procedures (Scheme 39). Cleavage of peptides from 71d can be accomplished with hydrazine and amino acid esters under mild conditions, which do not affect benzyl ester side-chain protecting groups. 

O-linked polymer-bound Af-substituted hydroxylamines are prepared by reduction of resin-bound oximes with borane-pyridine complex in the presence of dichloroacetic acid (Scheme 94). Other reducing systems commonly used for imine or oxime reduction are ineffective, including borane-pyridine in the presence of acetic acid. Subsequently, the A-substituted products are acylated and cleaved from the resin to afford Af-substituted hydroxamic acids 220. ... 

DeGrado, W. F. and Kaiser, E. T. (1982) Sohd phase synthesis of protected peptides on a polymer bound oxime preparation of segments comprising the sequence of a cytotoxic 26-peptide analog. J. Org. Chem. 47, 3258-3261. 

HCl-HOAc-AcjO, POCls, BiCla, neat with FeCls, and polyphosphoric acid. The reaction has been done in supercritical water and in ionic liquids. A polymer-bound Beckman rearrangement has been reported. Sim-ply heating the oxime of benzophenone neat leads to A-phenyl benzamide. The oximes of cyclic ketones give ring enlargement and form the lactam,as in the formation of caprolactam (83) from the oxime of cyclohexanone. Heating an... 

Dimethylsulphonium methylide methylates aromatic E-oximes in yields of 32—91% and trimethylsulphonium hydroxide methylates, in excellent yield, carboxylic acids, thiols, phenols, and certain heterocyclic nitrogen atoms. However, aromatic amines and alcohols remain unchanged. Polymer-bound reagents have proved popular in recent years such a reagent, a polymer-bound sulphonium ylide, provides excellent yields of epoxides from ketones. The spent reagent may then be regenerated for further use. Nitroalkanes are reduced, in... 

DeG1980 DeGrado, W.F. and Kaiser, E.T., Polymer-Bound Oxime Esters as Supports for Solid-Phase Peptide Synthesis. The Preparation of Protected Peptide Fragments, J. Org. Chem., 45 (1980) 1295-1300. 

Polymer-bound acyl oxime esters have also been reported to be suitable radical sources [216]. Polyesters containing acyl oxime oxides were prepared by a poly condensation reaction [230]. Irradiation of these compounds with 365 nm light in the presence of vinyl monomers (styrene) gave block copolymers. ... 

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. 

Usually oxime has a high nucleophilicity in dissociated form, but it is useless in a moderate aqueous solution for its high pK value (pK = 11 12). The oxime moiety which is bound to poly(4-vinylpyridine) by the quartemization shows a lower pK value (pK = 8.5 0.3) and high nucleophilicity in the hydrolysis of PNPA(5) (95). The catalytic activity of the polymer(X) reaches a half of that of a-chymotrypsin showing ka = 200 M-1 sec-1 at pH = 8, where m is 12. 

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