14684-48-1Relevant academic research and scientific papers
Flavin-iodine coupled organocatalysis for the aerobic oxidative direct sulfenylation of indoles with thiols under mild conditions
Ohkado, Ryoma,Ishikawa, Tatsuro,Iida, Hiroki
supporting information, p. 984 - 988 (2018/03/13)
A unique coupled redox organocatalysis system using flavin and iodine catalysts efficiently promoted the metal-free aerobic oxidative direct sulfenylation of indoles with thiols at ambient temperature without any sacrificial reagents, except environmentally benign molecular oxygen. Biomimetic flavin catalysis plays multiple roles in aerobic oxidative transformations, not only regenerating I2 from in situ generated I-, but also converting thiols into disulfides.
Comparison of riboflavin-derived flavinium salts applied to catalytic H2O2 oxidations
Sakai, Takuya,Kumoi, Takuma,Ishikawa, Tatsuro,Nitta, Takahiro,Iida, Hiroki
, p. 3999 - 4007 (2018/06/08)
A series of flavinium salts, 5-ethylisoalloxazinium, 5-ethylalloxazinium, and 1,10-ethylene-bridged alloxazinium triflates, were prepared from commercially available riboflavin. This study presents a comparison between their optical and redox properties, and their catalytic activity in H2O2 oxidations of sulfide, tertiary amine, and cyclobutanone. Reflecting the difference between the π-conjugated ring structures, the flavinium salts displayed very different redox properties, with reduction potentials in the order of: 5-ethylisoalloxazinium > 5-ethylalloxazinium > 1,10-ethylene-bridged alloxazinium. A comparison of their catalytic activity revealed that 5-ethylisoalloxazinium triflate specifically oxidises sulfide and cyclobutanone, and 5-ethylalloxazinium triflate smoothly oxidises tertiary amine. 1,10-Bridged alloxazinium triflate, which can be readily obtained from riboflavin in large quantities, showed moderate catalytic activity for the H2O2 oxidation of sulfide and cyclobutanone.
Electron-deficient alloxazinium salts: Efficient organocatalysts of mild and chemoselective sulfoxidations with hydrogen peroxide
Menova, Petra,Dvorakova, Hana,Eigner, Vaclav,Ludvik, Jiri,Cibulka, Radek
, p. 3451 - 3462 (2013/12/04)
A series of substituted alloxazinium perchlorates has been prepared and tested as catalysts for the oxidation of sulfides to sulfoxides with hydrogen peroxide. The logarithms of the observed rate constants of thioanisole oxidation correlate with the Hammett σ constants of the substituents on the alloxazinium catalysts, as well as with their reduction potentials E 0′ and their pKR+ values, representing the alloxazinium salt/pseudobase equilibrium. The stronger the electron-withdrawing substituent, the more efficient is the alloxazinium catalyst. The alloxazinium salts with a cyano or trifluoromethyl group in position 8 proved to be the most efficient, operating at room temperature at small loadings, down to 0.1 mol%, achieving turnover number values of up to 640 and acceleration by a factor of 350 relative to the non-catalyzed oxidation. The 8-cyanoalloxazinium perchlorate was evaluated as the best catalyst; however, due to its relatively good accessibility, the 8-(trifluoromethyl)alloxazinium perchlorate seems to be the catalyst of choice for sulfoxidations with hydrogen peroxide. It was successfully tested for the sulfoxidation of a series of aliphatic and aromatic sulfides on a preparative scale. It produced the corresponding sulfoxides in quantitative conversions and with high isolated yields (87-98%). No over-oxidation to sulfone was ever observed. Copyright
Organocatalytic Dakin oxidation by nucleophilic flavin catalysts
Chen, Shuai,Hossain, Mohammad S.,Foss, Frank W.
supporting information; experimental part, p. 2806 - 2809 (2012/08/07)
Flavin catalysts perform the first organocatalytic Dakin oxidation of electron-rich arylaldehydes to phenols under mild, basic conditions. Catechols are readily prepared, and the oxidation of 2-hydroxyacetophenone was achieved. Aerobic oxidation is displayed in the presence of Zn(0) as a reducing agent. This reactivity broadens the scope of biomimetic flavin catalysis in the realm of nucleophilic oxidations, providing a framework for mechanistic investigations for related oxidations, such as the Baeyer-Villiger oxidation and Weitz-Scheffer epoxidation.
Aerobic organocatalytic oxidation of aryl aldehydes: Flavin catalyst turnover by Hantzsch's ester
Chen, Shuai,Foss, Frank W.
supporting information, p. 5150 - 5153,4 (2020/09/15)
The first Dakin oxidation fueled by molecular oxygen as the terminal oxidant is reported. Flavin and NAD(P)H coenzymes, from natural enzymatic redox systems, inspired the use of flavin organocatalysts and a Hantzsch ester to perform transition-metal-free, aerobic oxidations. Catechols and electron-rich phenols are achieved with as low as a 0.1 mol % catalyst loading, 1 equiv of Hantzsch ester, and O2 or air as the stoichiometric oxidant source.
Turning a riboflavin-binding protein into a self-sufficient monooxygenase by cofactor redesign
De Gonzalo, Gonzalo,Smit, Christian,Jin, Jianfeng,Minnaard, Adriaan J.,Fraaije, Marco W.
supporting information; experimental part, p. 11050 - 11052 (2011/12/01)
By cofactor redesign, self-sufficient monooxygenases could be prepared. Tight binding of N-alkylated flavins to riboflavin-binding protein results in the creation of artificial flavoenzymes capable of H2O 2-driven enantioselective sulfoxidations. By altering the flavin structure, opposite enantioselectivities could be achieved, in accordance with the binding mode predicted by in silico flavin-protein docking of the unnatural flavin cofactors. The study shows that cofactor redesign is a viable approach to create artificial flavoenzymes with unprecedented activities.
A NEW SYNTHESIS OF FERVENULINS AND ALLOXAZINES. THERMOLYSIS AND PHOTOLYSIS OF 6-AZIDO-1,3-DIMETHYLURACIL WITH TETRAZOLES AND BENZOTRIAZOLES
Hirota, Kosaku,Maruhashi, Kazuo,Asao, Tetsuji,Senda, Shigeo
, p. 285 - 288 (2007/10/02)
Thermolysis of 6-azido-1,3-dimethyluracil(1) in the presence of 5-substituted tetrazoles(2) gave 3-substituted fervenulins(4), which were also synthesized from the intermediates(3) prepared by photolysis of (1) with (2).Irradiation of (1) with benzotriazoles(6) in tetrahydrofuran gave 6-(benzotriazol-1-yl)uracils(7), which were irradiated in methanol to afford alloxazines (8).
Model compounds of biological molybdenum. I. Flavin and mixed-ligand complexes of molybdenum(IV) and -(V)
Selbin,Sherrill, Jon,Bigger, Cynthia H.
, p. 2544 - 2549 (2007/10/05)
The first solid flavin complexes of molybdenum(IV) have been isolated and characterized by dta, tga, ir, vis-uv, nmr, and epr data. Their general formulation is MoOCl3(H-flavine), with the organic ligand being a monocation complexed as a bidentate ligand through its primary binding site, C=O(4) and N(5). Ir data are cited in support of this mode of bonding. The first solid molybdenum(V)-flavine complex has been isolated and partially characterized; its epr spectrum suggests that it is monomeric. Mixed-ligand complexes of oxomolybdenum(IV) containing both a flavine molecule and a sulfur-donor ligand have been synthesized for the first time. It is believed that these compounds may approximate the first coordination sphere environment of molybdenum in certain biological-molybdenum species.
