Home  About us  Contact
 

Oxygenation Reactions (oxygenation + reaction)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

ChemInform Abstract: Regioselective Synthesis and Structural Studies of Substituted ,-Hydroxybutenolides with Use of a Tandem Baylis,Hillman/Singlet Oxygenation Reaction.

CHEMINFORM, Issue 42 2008
Santoshkumar N. Patil
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Extended Hartree,Fock theory of chemical reactions.

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 15 2009

Abstract Symmetry and broken symmetry (BS) in molecular orbital description of transition structures and intermediates in oxygenation reactions have been revisited to elucidate states correlation diagrams and mechanisms for addition reactions of molecular oxygen and metal-oxo MO (M = Mn(II) and Fe(II)) species to CC double bonds. Relative stabilities between diradical (DR) and perepoxide (PE) intermediates were thoroughly investigated by several BS hybrid DFT (HDFT) methods and BS CCSD(T) method with and without spin projection. It has been found that recovery of spin symmetry, namely eliminating spin contamination error from the BS solutions, is crucial for the elucidation of reasonable state correlation diagrams and energy differences of the key structures in the oxygenation reactions because the singlet-triplet energy gap for molecular oxygen is large (22 kcal/mol). The BS HDFT followed by spin correction reproduced activation barriers for transition structures along both PE and DR reaction pathways by the use of the CASPT2 method. Basis set dependence on the relative stability between PE and DR intermediates were also examined thoroughly. Solvation effect for DR and PE intermediates was further examined with self-consistent reaction field (SCRF) and SCIPCM methods. Both BS HDFT and CASPT2 have concluded that the DR mechanism is favorable for the addition reaction of singlet oxygen to ethylene, supporting our previous conclusions. The BS HDFT with spin correction was concluded to be useful enough for theoretical investigations of mechanisms of oxygenation reactions. Implications of the computational results were discussed in relation to the theoretical framework (four configuration model) for elucidation of possible mechanisms of epoxidation reactions with Fe(IV)O cores in metalloenzymes on the basis of isolobal analogies among O, OO, and Fe(IV)O. Correspondence between magnetic coupling mode and radical pathway in oxygenations with these species was clarified based on the BS MO interaction diagrams, leading to local singlet and triplet diradical mechanisms for epoxidations. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [source]

Binuclear Iron(III) Phthalocyanine(,-Oxodimer)-Catalyzed Oxygenation of Aromatic Hydrocarbons with Iodosylbenzene Sulfate and Iodosylbenzene as the Oxidants

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2009
Heather
Abstract Two binuclear iron(III) phthalocyanine-(,-oxodimer) complexes were tested in catalytic oxygenation reactions of several aromatic hydrocarbons using iodosylbenzene (PhIO)n or oligomeric iodosylbenzene sulfate [(PhIO)3SO3]n as the oxidants. Results of this study demonstrate that [(PhIO)3SO3]n is the most reactive oxygenating reagent that can be used as a safe and convenient alternative to the thermally unstable and potentially explosive iodosylbenzene. The pyridine-containing binuclear ,-oxobis{iron(III)-pyridino[3,4]-9(10),16(17),23(24)-tri- tert -butyltribenzoporphyrazine} is significantly more active as compared to the traditional ,-oxobis[iron(III)-2,9(10),16(17),23(24)-tetra- tert -butylphthalocyanine]. [source]

Expression, purification and crystallization of the cofactor-independent monooxygenase SnoaB from the nogalamycin biosynthetic pathway

ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 3 2009
Hanna Koskiniemi
12-deoxy-nogalonic acid oxygenase (SnoaB) catalyzes the oxygenation of 12-deoxy-nogalonic acid at position 12 to yield nogalonic acid, which is one of the steps in the biosynthesis of the polyketide nogalamycin in Streptomyces nogalater. SnoaB belongs to a family of small cofactor-free oxygenases which carry out oxygenation reactions without the aid of any prosthetic group, cofactor or metal ion. Recombinant SnoaB was crystallized in space group P21212, with unit-cell parameters a = 58.8, b = 114.1, c = 49.5,Å, and these crystals diffracted to 2.4,Å resolution. Recombinant SnoaB does not contain any methionine residues and three double mutants were designed and produced for the preparation of selenomethionine-substituted samples. The selenomethionine-substituted mutant F40M/L89M crystallized in the same space group as the native enzyme. [source]