Me(2)-NHC proved to be a valuable ligand in iridium catalyzed water oxidation reactions, both when carried out electrochemically as well as upon oxidation with cerium ammonium nitrate. Mechanistic ...data suggest that water oxidation occurs efficiently at a well defined iridium species via a mononuclear pathway.
Ceric ammonium nitrate (CAN)-promoted oxidative
-cyclization of unactivated biaryl ynones with
-centered radicals (SCN/SCF
) to access spiro5,5trienones has been established. This approach displayed ...excellent regioselectivity towards spirocyclization and tolerated a variety of functional groups. Dearomatization of hitherto unknown aryl/heteroaryl groups is also disclosed. DMSO is employed as a low-toxicity, inexpensive solvent as well as a source of oxygen.
Ketones with remote fluorination are an important motif in the synthesis of bioactive molecules. Here we demonstrate that ceric ammonium nitrate (CAN) is able to produce this functionality under ...incredibly mild conditions and short reaction times (30 min) while eliminating the need for precious metals in previous methods. Importantly, this method allows the efficient synthesis of a wide variety of γ-fluoroketones and is highly scalable. Preliminary mechanistic studies suggest this reaction proceeds through a radical pathway.
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•Mechanism of cerium(IV) ammonium nitrate (CAN) photolysis in CH3CN is presented.•Inner-sphere electron transfer was found to be the primary photochemical process.•High quantum yield ...of NO3 formation (0.6 and 0.4 upon 308 and 355 nm excitation).•Rate constants of reactions responsible for NO3 decay are measured.•A part of excited CAN molecules form the radical complex (NH4)2CeIII(NO3)5…NO3.
Cerium ammonium nitrate (NH4)2CeIV(NO3)6 (CAN) is widely used as a photolytic source of NO3 radicals in acetonitrile. In spite of that, the mechanistic aspects of CAN photochemistry were poorly discussed in the literature. In this work CAN photochemistry in CH3CN was studied using the combination of stationary methods and laser flash photolysis. In accordance with the literature, the inner-sphere electron transfer was found to be the primary photochemical process. The (NH4)2CeIII(NO3)5(CH3CN) complex was found to be the only reaction product formed with the rather high quantum yield (0.6 and 0.4 upon 308 and 355 nm excitation correspondingly). The NO3 radicals decay is mainly caused by the second-order reactions; their rate constants are determined. In addition to the direct release of the NO3 radicals, a part of the light-excited CAN molecules were found to form the radical complex (NH4)2CeIII(NO3)5…NO3, which lifetime is ca. 2 μs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
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•New methods for the synthesis of pyridopyrimidinediones and pyridopyrimidinetriones.•Critical intermediates in drug development.•Oxidative aromatization using ceric ammonium nitrate.
...Pyridopyrimidine-2,4(1H,3H)-diones and pyrido4,3–dpyrimidine-2,4,5(1H,3H,6H)-triones are valuable scaffolds which can be used in drug development. In this letter a simple and efficient method for the synthesis of pyrido4,3–dpyrimidine-2,4-diones and pyrido4,3–dpyrimidine-2,4,5(1H,3H,6H)-triones by oxidative aromatization of easily synthesized 5,6,7,8-tetrahydropyrido4,3–dpyrimidine-2,4(1H,3H)-dione derivatives was reported.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
The generation of solar fuels by means of a photosynthetic apparatus strongly relies on the development of an efficient water oxidation catalyst (WOC). Cerium ammonium nitrate (CAN) is the most ...commonly used sacrificial oxidant to explore the potentiality of WOCs. It is usually assumed that CAN has the unique role to oxidatively energize WOCs, making them capable to offer a low-energy reaction pathway to transform H2O to O2. Herein, we show that CAN might have a much more relevant and direct role in WO, mainly related to the capture and liberation of O–O-containing molecular moieties.
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IJS, KILJ, NUK, PNG, UL, UM
Chiral α-aryl glycines play a key role in the preparation of some bioactive products, however, their catalytic asymmetric synthesis is far from being satisfactory. Herein, we report an efficient ...nickel-catalyzed asymmetric hydrogenation of N-aryl imino esters, affording chiral α-aryl glycines in high yields and enantioselectivities (up to 98% ee). The hydrogenation can be conducted on a gram scale with a substrate/catalyst ratio of up to 2000. The obtained chiral N-p-methoxyphenyl α-aryl glycine derivatives are not only directly useful chiral secondary amino acid esters but can also be easily deprotected by treatment with cerium ammonium nitrate for further transformations to several widely used molecules including drug intermediates and chiral ligands. Formation of a chiral Ni-H species in hydrogenation is detected by
H NMR. Computational results indicate that the stereo selection is determined during the approach of the substrate to the catalyst.
An efficient and scalable method for the synthesis of 3,4-dihydroisoquinolin-1(2
H
)-ones through benzylic oxidation of tetrahydroisoquinoline derivatives using a catalytic amount of cerium ammonium ...nitrate (CAN) and a stoichiometric amount of NaBrO
3
as oxidants was developed. The reaction is significantly influenced by the substituent groups on the phenyl ring. While electron-withdrawing groups on the phenyl ring can lower the reactivities of the substrates, electron-donating groups on the phenyl ring can dramatically promote the oxidation rate.
A series of benzolactams were synthesized by the oxidation of tetrahydroisoquinoline derivates with CAN (cat.) and NaBrO
3
.
Abstract
A Cerium(IV)‐promoted phosphinoylation‐nitratation of alkenes is established under mild conditions. In this process, Ceric ammonium nitrate (CAN) acts as a cheap phosphorus‐radical ...initiator, as well as a nitrate donor. Various β‐nitrooxyphosphonates are delivered in high yield in a one‐pot manner.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Water oxidation is one of the most important reactions needed for a transition to a green economy. The reaction relies on extracting electrons from oxygen anions and is commonly studied using ...homogenous catalysts based on Ru or Ir metals. Because of Ir scarcity and its relative instability in acidic environments, metals to replace it are sought after. In this study, we have synthesized Au-Pd-based catalysts deposited on TiO2 with different ratios in order to mimic IrO2 valence orbitals (Ir5d) by the hybrid valence orbitals of Au5d and Pd4d and compared their heterogeneous catalytic activity for the evolution of O2 from water in the presence of cerium ammonium nitrate (CAN). Au-Pd-based catalysts were found to be active at a particular nominal atomic ratio. At an atomic ratio of 1 Au to 2 Pd and 1 Au to 3 Pd, the catalysts were active and stable for oxygen production from water. Long-term runs up to 20,000 min still showed the expected stoichiometry between O2 production and CAN consumption (1 to 4). However, catalysts with a reverse ratio were not active. Also, the monometallic catalysts were found to be not active for the reaction. We link the reason for the activity of Au-Pd with this specific ratio to the shape and energy position of their valence band that might be similar to those of IrO2 particles. While the turnover numbers of the Au-Pd-based catalysts were found to be lower than those of IrO2-based catalysts, on the same support in a heterogenous system, there is considerable potential upon further optimization for these two metals to replace IrO2 for a water oxidation reaction.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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