SYNOPSISl-Acryloyl-4-acryloyloxy-2,2,6,6-tetramethylpiperidine (AATP) has been covalently attached to polypropylene under conditions of reactive processing to give substantial concentrations of essentially 100% grafted antioxidant ( AATP-B) . Solution of the concentrates showed that at high concentration of grafted antioxidant some homopolymerized AATP was present and the polymer undergoes transient cross-linking during processing. Concentrates of bound AATP ( AATB-B) when used as conventional additives for polypropylene are very effective photoantioxidants due to conversion to the related polymer-bound nitroxyl radicals by photosensitized oxidation. A typical commercial hindered phenol, Irganox 1076, when used at low concentration in combination with AATP-B also acts as a photosensitizer for nitroxyl formation. Unlike low molar mass-hindered piperidinoxyl, polymer-bound nitroxyls are effective thermal antioxidants that synergize very effectively with low concentrations of Irganox 1076.
Oxadiazole derivatives R 0290 Synthesis and Evaluation of Phenyl-Substituted Sydnones as Potential DPPH-Radical Scavengers. -Nine compounds show interesting 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity. -(MALLUR, S. G.; TIWARI, A. K.; RAJU, B. C.; BABU, K. S.; ALI, A. Z.; SASTRY, B. S.; RAO*, M. J.; Indian J. Chem., Sect.
diastereoselective syntheses, enantioselective syntheses diastereoselective syntheses, enantioselective syntheses (incl. cis/trans-isomerism) O 0031
-024Asymmetric Reduction of Prochiral Ketones Using in situ Generated Oxazaborolidines Derived from Amino Alcohols of (1R)-Camphor as Catalysts.-Various oxazaborolidines, generated in situ from three isomeric amino alcohols derived from (1R)-(+)-camphor and having different orientations of the hydroxy and amino groups, are used as catalysts in the title reaction. It is found that cis-endo-endo derivative cat. 1 and cis-exo-exo derivative cat. 4 are effective catalysts for the asymmetric reduction of ketones. The effect of various parameters such as temperature, catalyst-substrate ratio and chirality of the catalyst precursor on the enantioselectivity of the reduction are also studied. -(SANTHI, V.; RAO, MADHUSUDANA J.; Tetrahedron:
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