Aerobic Organocatalytic Oxidation of Aryl Aldehydes: Flavin Catalyst Turnover by Hantzsch’s Ester
摘要:
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 O-2 or air as the stoichiometric oxidant source.
N5-Modified alloxazinium salts including 5-ethyl-1,3-dimethylalloxazinium and 5-ethyl-1,3-dimethyl-8-(trifluoromethyl)alloxazinium salts were readily prepared as alloxazinium-resins from the corresponding N5-unmodified ingredients via the aerobic oxidation—ion exchange protocol, previously introduced by us for the preparation of isoalloxazine analogues, and their catalysis and reusability in H2O2 oxidations
Ñ 5改性alloxazinium盐,包括alloxazinium盐容易地制备5-乙基-1,3- dimethylalloxazinium和5-乙基-1,3-二甲基-8-(三氟甲基)alloxazinium树脂从相应Ñ经由5未改性的成分我们评估了先前由我们引入的用于制备异恶嗪类似物的好氧氧化-离子交换方案,以及它们在H 2 O 2氧化中的催化作用和可重复使用性。
Organometallic iridium(III) and rhenium(I) complexes with lumazine, alloxazine and pterin derivatives
作者:Oliver Heilmann、Fridmann M. Hornung、Jan Fiedler、Wolfgang Kaim
DOI:10.1016/s0022-328x(99)00294-6
日期:1999.10
Two organometallic complex fragments with 5d6 configurated metal centres of different character, electrophilic [IrIIICp*Cl]+ and π-donating [ReI(CO)3Cl], were used as probes in compounds containing 1,3-dimethyllumazine (DML), 1,3-dimethylalloxazine (DMA), 2-pivaloylpterin (PP) and 6-methyl-2-pivaloylpterin (MPP) as biochemically relevant ligands. Evidence from spectroscopy (NMR, IR, UV–vis) in aprotic
在含有1,3-二甲基azine嗪的化合物中,使用两个具有5d 6构型金属中心的不同特性的两个有机金属配合物片段,分别为亲电子[Ir III Cp * Cl] +和π供体[Re I(CO)3 Cl]。 DML),1,3-二甲基脲嗪(DMA),2-吡咯戊蝶呤(PP)和6-甲基-2-吡咯烷蝶呤(MPP)作为生物化学相关配体。非质子溶剂中的光谱学(NMR,IR,UV-vis)证据表明,在大多数情况下,O4和N5原子是金属结合的螯合物。对于[(DMA)Ir III Cp * Cl](PF 6)通过晶体结构分析证实。然而,使用PP,获得了具有新戊酰基配位的金属的铱(III)化合物。好的π受体配体DMA的Ir III和Re I络合物都可以可逆地还原,因此可以通过(光谱)电化学(IR,UV-vis,EPR:以配体为中心的单电子还原)进行研究,而DML系统具有这种行为仅适用于Ir III物种。2-piv
Biomimetic aerobic oxidative hydroxylation of arylboronic acids to phenols catalysed by a flavin derivative
Flavin-catalysed oxidative hydroxylation of substituted arylboronic acids by molecular oxygen with the assistance of hydrazine or ascorbic acid resulted in phenols in high yields. This mild organocatalytic protocol is compatible with a variety of functional groups and it is alternatively usable for transformation of alkylboronic acids to alcohols. Reaction takes place also in water and fulfils criteria for a green procedure.
Photocatalytic Oxidative [2+2] Cycloelimination Reactions with Flavinium Salts: Mechanistic Study and Influence of the Catalyst Structure
作者:Tomáš Hartman、Martina Reisnerová、Josef Chudoba、Eva Svobodová、Nataliya Archipowa、Roger Jan Kutta、Radek Cibulka
DOI:10.1002/cplu.202000767
日期:2021.3
and investigated their application in light‐dependent oxidative cycloelimination of cyclobutanes. Detailed mechanistic investigations with a coumarin dimer as a model substrate reveal that the reaction preferentially occurs via the triplet‐born radical pair after electron transfer from the substrate to the triplet state of an alloxazinium salt. The very photostable 7,8‐dimethoxy derivative is a superior
Construction of pyrimido[5,4-<i>e</i>]-<i>as</i>-triazine, purine,<i>v</i>-triazolo-[4,5-<i>d</i>]pyrimidine and pyrazolo[3,4-<i>d</i>]pyrimidine ring systems from 5-arylazo-6-arylidenehydrazino-1,3-dimethyluracils
Reaction of 5-arylazo-6-arylidenehydrazino-1,3-dimethyluracils (II), prepared by the treatment of 6-aryl-idenehydrazino-1,3-dimethyluracils (I) with diazotized arylamines, with dimethylformamide dimethylacetal resulted in the formation of pyrimido[5,4-e]-as-triazine (V) system, while the thermolysis of II resulted in the formation of purine (X), v-triazolo[4,5-d]pyrimidine (XII), and pyrazolo[3,4-d]pyrimidine
通过用重氮化的芳胺处理6-芳基-亚氨基肼基-1,3-二甲基尿嘧啶(I)制备的5-芳基偶氮-6-亚芳基肼基-1,3-二甲基尿嘧啶(II)与二甲基甲酰胺二甲基缩醛反应形成以嘧啶[5,4- e ]-为-三嗪(V)体系,而II的热解导致嘌呤(X),v-三唑并[4,5- d ]嘧啶(XII)和吡唑并[ 3,4- d ]嘧啶(XIV,XIX)系统代替了预期的V。已提出了在这些反应中形成各种环系统的合理机理。