37073-23-7Relevant academic research and scientific papers
Mechanistic insight into aerobic alcohol oxidation using NOx-nitroxide catalysis based on catalyst structure-activity relationships
Shibuya, Masatoshi,Nagasawa, Shota,Osada, Yuji,Iwabuchi, Yoshiharu
, p. 10256 - 10268 (2015/02/19)
The mechanism of an NOx-assisted, nitroxide(nitroxyl radical)-catalyzed aerobic oxidation of alcohols was investigated using a set of sterically and electronically modified nitroxides (i.e., TEMPO, AZADO (1), 5-F-AZADO (2), 5,7-DiF-AZADO (3), 5-MeO-AZADO (4), 5,7-DiMeO-AZADO (5), oxa-AZADO (6), TsN-AZADO (7), and DiAZADO (8)). The motivation for the present study stemmed from our previous observation that the introduction of an F atom at a remote position from the nitroxyl radical moiety on the azaadamantane nucleus effectively enhanced the catalytic activity under typical NOx-mediated aerobic-oxidation conditions. The kinetic profiles of the azaadamantane-N-oxyl-[AZADO (1)-, 5-F-AZADO (2)-, and 5,7-DiF-AZADO (3)]-catalyzed aerobic oxidations were closely investigated, revealing that AZADO (1) showed a high initial reaction rate compared to 5-F-AZADO (2) and 5,7-DiF-AZADO (3); however, AZADO-catalyzed oxidation exhibited a marked slowdown, resulting in ～90% conversion, whereas 5-F-AZADO-catalyzed oxidation smoothly reached completion without a marked slowdown. The reasons for the marked slowdown and the role of the fluoro group are discussed. Oxa-AZADO (6), TsN-AZADO (7), and DiAZADO (8) were designed and synthesized to confirm their comparable catalytic efficiency to that of 5-F-AZADO (2), providing supporting evidence for the electronic effect on the catalytic efficiency of the heteroatoms under NOx-assisted aerobic-oxidation conditions.
O-capped heteroadamantyl-substituted hydrazines and their oxidation products
Li, Gaoquan,Nelsen, Stephen F.,Jalilov, Almaz S.,Guzei, Ilia A.
experimental part, p. 2445 - 2452 (2010/07/08)
The mixed valence bishydrazine radical cation 6+, obtained by oxidation of 2,6-bi-(2′-oxa-6′-azaadamantane-6′-yl)-2,6- diazaadamantane-2,6-diyl (6) with silver or nitrosonium salts, has been prepared and studied. 6 is obtained along with lesser amounts of the trishydrazine, some of the tetrahydrazine, and apparently traces of the pentahydrazine upon reaction of deprotonated 2-oxa-6-azaadamantane with 2,6-dichloro-2,6- diazaadamantane. The EPR spectrum of 6+ shows that its charge is localized on one hydrazine unit on the EPR time scale. It shows a Hush-type Robin?Day class II mixed valence band in its optical spectrum despite the fact that the nitrogen lone pairs are held in a perpendicular geometry that would lead to no electronic interaction between the nitrogen atoms that are separated by only four ? bonds if its nitrogens were planar. The electron transfer distance that is estimated from the calculated dipole moment of 6+ is the same as that obtained using the average distance between the electrons of the triplet state of the dication 62+, calculated from its dipolar EPR splitting, as a model for the electron transfer distance of 6+, 3.7 . Using Hush Gaussian approximation for the optical spectrum with this electron transfer distance produces an estimate of the electronic coupling Vab through the saturated bridge of about 400 cm?1, which is consistent with the observed EPR spectrum of 6+. From the observed dipolar splitting, the trishydrazine diradical dication has its remote hydrazine units oxidized, although the monocation presumably forms at the central hydrazine unit, which lacks substitution by the more electron-withdrawing oxygen atoms.
