Poly transfer hydrogenation

A chiral diaminodiphosphine ligand was attached onto poly(acrylic acid) through an amide linkage. The ruthenium(II) complex of the resultant polymeric ligand (169) was then applied to the asymmetric transfer hydrogenation of acetophenone in 2-propanol (Scheme 3.51) [101]. (S)-l-phenylethanol was obtained in 95% yield with 96% ee by using 158. 

In order to facilitate recycling of the multiple TsDPEN-functionalized dendrimer catalysts, the same group recently reported the synthesis of a novel form of hybrid dendrimer ligands by coupling polyether dendrons with peripherally TsDPEN-functionahzed Newkome-type poly(ether-amide) dendrimer (Figure 4.28) [90]. The solubility of these hybrid dendrimers was found to be affected by the generation of the polyether dendron. The ruthenium complexes produced were applied in the asymmetric transfer hydrogenation of ketones, enones, imines and activated... 

Such reactions, however, can also be used for synthetic purposes. For example, p-diisopropyl benzene has two easily transferable hydrogen atoms. The hydrogen atoms are transferred in the reaction with initiator free radicals, and diradicals are formed. The monomer diradicals then recombine in what is called polyrecombination to poly(diradicals) ... 

Malacca, R., Poli, R., Manoury, E. (2010). Asymmetric hydrosilylation, transfer hydrogenation and hydrogenation of ketones catalyzed by iridium complexes. Coordination Chemistry Reviews, 254, 729—752. http //dx.doi.Org/10.1016/j.ccr.2009.09.033. 

Acrylamide readily undergoes polymerization by conventional free radical methods, ionizing radiation, ultrasonic waves, and ultraviolet radiation. The base-cata-lized hydrogen transfer polymerization of acrylamide yields poly-/3-alanine (Nylon 3) a water insoluble polymer that is soluble in certain hot organics. All current industrial production is believed to be by free radical polymerization. 

Similarly, energy-transfer processes, together with electron transfer and hydrogen abstraction reactions could be induced in poly(organophosphazenes) in an intramolecular way by preparing POPs geminally substituted at the same phosphorus with two different substituent groups. 

Other supramolecular structures such as dendrimers have also been synthesized with zinc-containing porphyrins. Sixteen free base and sixteen zinc porphyrin units were added at the fifth generation of dendritic poly(L-lysine) and intramolecular fluorescence energy transfer was observed.823 Assembly of supramolecular arrays in the solid state has been achieved with the incorporation of an amide group for hydrogen bonding. Zinc meso-tetra(4-amidophenyl)porphyrin... 

Frequently B will also undergo a back hydrogen transfer which regenerates the parent ketone, as well as cyclization (in most cases a minor reaction) as a result of this competition the quantum yields of fragmentation are typically in the 0.1-0.5 range in non-polar media. When the Norrish Type II process takes place in a polymer it can result in the cleavage of the polymer backbone. Poly(phenyl vinyl ketone) has frequently been used as a model polymer in which this reaction is resonsible for its photodegradation, reaction 2. 

Fig. 1.16 Schematic representation of the nanofibrous poly (acrylonitrile-co-acrylic acid) membrane containing MWCNTs, as well as the promoted electron transfer from hydrogen peroxide to the immobilized catalase through the PANCAA/MWCNTs nanofiber. Reprinted from [209] (reproduced by permission ofWiley-VCH).

CHR—CO—), polyoxy acids (—O—CHR—CO—), poly-l-alkylbuta-dienes (—CH=CH—CHR—CH2—). To the same class iKlong the polymers with two asymmetric atoms for every monomer unit, such as polysoibates (—CH=CH—CHA—CHB—, 32 and 33) where both eiythio- and thieo-diisotactic forms are chiral, or polyhexadiene (—CH=CH—CHA—CHA—) and poly-2,3-epoxybutane (—O— CHA-CHA-), 39, where only the thieo-diisotactic structures are chiral, and the polymers of some bicyclic monomers such as those shown in 41 and 42. Other examples are the polymers obtained by hydrogen transfer fk m substituted benzalacetone (79, Scheme 17) (266, 267). 

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