930-30-3Relevant articles and documents
Independent generation of triplet 1,4-biradical intermediates implicated in the photochemical cycloaddition reaction between 2-cyclopentenone and acrylonitrile
Krug,Rudolph,Weedon
, p. 7221 - 7224 (1993)
Norrish Type 1 photochemistry of 3-cyanobicyclo[3.3.0]octane-2,6-dione and 3-cyanobicyclo[3.3.0]octane-2,8-dione is used to generate triplet 1,4-biradicals implicated in the photochemical cycloaddition reaction of 2-cyclopentenone with acrylonitrile. The fates of these biradicals have been determined and they suggest that the photocycloaddition reaction regiochemistry is governed by competition between closure of the biradicals to product and their reversion to ground state starting materials. This provides further evidence against the long-held view that the relative rates of formation of the biradicals mediated by an oriented triplet exciplex governs the reaction regiochemistry. It is also found that the regiochemistry of the photochemical cycloaddition reaction between cyclopentenone and acrylonitrile is reversed from that obtained in the addition of acrylonitrile to 2-cyclohexenone.
Electrochemically driven desaturation of carbonyl compounds
Gnaim, Samer,Takahira, Yusuke,Wilke, Henrik R.,Yao, Zhen,Li, Jinjun,Delbrayelle, Dominique,Echeverria, Pierre-Georges,Vantourout, Julien C.,Baran, Phil S.
, p. 367 - 372 (2021/03/31)
Electrochemical techniques have long been heralded for their innate sustainability as efficient methods to achieve redox reactions. Carbonyl desaturation, as a fundamental organic oxidation, is an oft-employed transformation to unlock adjacent reactivity through the formal removal of two hydrogen atoms. To date, the most reliable methods to achieve this seemingly trivial reaction rely on transition metals (Pd or Cu) or stoichiometric reagents based on I, Br, Se or S. Here we report an operationally simple pathway to access such structures from enol silanes and phosphates using electrons as the primary reagent. This electrochemically driven desaturation exhibits a broad scope across an array of carbonyl derivatives, is easily scalable (1–100 g) and can be predictably implemented into synthetic pathways using experimentally or computationally derived NMR shifts. Systematic comparisons to state-of-the-art techniques reveal that this method can uniquely desaturate a wide array of carbonyl groups. Mechanistic interrogation suggests a radical-based reaction pathway. [Figure not available: see fulltext.]
g-C3N4/metal halide perovskite composites as photocatalysts for singlet oxygen generation processes for the preparation of various oxidized synthons
Corti, Marco,Chiara, Rossella,Romani, Lidia,Mannucci, Barbara,Malavasi, Lorenzo,Quadrelli, Paolo
, p. 2292 - 2298 (2021/04/12)
g-C3N4/metal halide perovskite composites were prepared and used for the first time as photocatalysts forin situ1O2generation to perform hetero Diels-Alder, ene and oxidation reactions with suitable dienes and alkenes. The standardized methodology was made applicable to a variety of olefinic substrates. The scope of the method is finely illustrated and the reactions afforded desymmetrized hydroxy-ketone derivatives, unsaturated ketones and epoxides. Some limitations were also observed, especially in the case of the alkene oxidations, and poor chemoselectivity was somewhere observed in this work which is the first application of MHP-based composites forin situ1O2generation. The experimental protocol can be used as a platform to further expand the knowledge and applicability of MHPs to organic reactions, since perovskites offer a rich variety of tuning strategies which may be explored to improve reaction yields and selectivities.
Reductive Electrochemical Activation of Molecular Oxygen Catalyzed by an Iron-Tungstate Oxide Capsule: Reactivity Studies Consistent with Compound i Type Oxidants
Bugnola, Marco,Shen, Kaiji,Haviv, Eynat,Neumann, Ronny
, p. 4227 - 4237 (2020/05/05)
The reductive activation of molecular oxygen catalyzed by iron-based enzymes toward its use as an oxygen donor is paradigmatic for oxygen transfer reactions in nature. Mechanistic studies on these enzymes and related biomimetic coordination compounds designed to form reactive intermediates, almost invariably using various "shunt" pathways, have shown that high-valent Fe(V)=O and the formally isoelectronic Fe(IV) =O porphyrin cation radical intermediates are often thought to be the active species in alkane and arene hydroxylation and alkene epoxidation reactions. Although this four decade long research effort has yielded a massive amount of spectroscopic data, reactivity studies, and a detailed, but still incomplete, mechanistic understanding, the actual reductive activation of molecular oxygen coupled with efficient catalytic transformations has rarely been experimentally studied. Recently, we found that a completely inorganic iron-tungsten oxide capsule with a keplerate structure, noted as {Fe30W72}, is an effective electrocatalyst for the cathodic activation of molecular oxygen in water leading to the oxidation of light alkanes and alkenes. The present report deals with extensive reactivity studies of these {Fe30W72} electrocatalytic reactions showing (1) arene hydroxylation including kinetic isotope effects and migration of the ipso substituent to the adjacent carbon atom ("NIH shift"); (2) a high kinetic isotope effect for alkyl C - H bond activation; (3) dealkylation of alkylamines and alkylsulfides; (4) desaturation reactions; (5) retention of stereochemistry in cis-alkene epoxidation; and (6) unusual regioselectivity in the oxidation of cyclic and acyclic ketones, alcohols, and carboxylic acids where reactivity is not correlated to the bond disassociation energy; the regioselectivity obtained is attributable to polar effects and/or entropic contributions. Collectively these results also support the conclusion that the active intermediate species formed in the catalytic cycle is consistent with a compound I type oxidant. The activity of {Fe30W72} in cathodic aerobic oxidation reactions shows it to be an inorganic functional analogue of iron-based monooxygenases.
K2S2O8-promoted C-Se bond formation to construct α-phenylseleno carbonyl compounds and α,β-unsaturated carbonyl compounds
Yang, Xue-Yan,Wang, Ruizhe,Wang, Lu,Li, Jianjun,Mao, Shuai,Zhang, San-Qi,Chen, Nanzheng
, p. 28902 - 28905 (2020/08/25)
A novel K2S2O8-promoted C-Se bond formation from cross-coupling under neutral conditions has been developed. A variety of aldehydes and ketones react well using K2S2O8 as the oxidant in the absence of catalyst and afford desired products in moderate to excellent yields. This protocol provides a very simple route for the synthesis of α-phenylseleno carbonyl compounds and α,β-unsaturated carbonyl compounds.
Quantitative production of butenes from biomass-derived γ-valerolactone catalysed by hetero-atomic MFI zeolite
Lin, Longfei,Sheveleva, Alena M.,da Silva, Ivan,Parlett, Christopher M. A.,Tang, Zhimou,Liu, Yueming,Fan, Mengtian,Han, Xue,Carter, Joseph H.,Tuna, Floriana,McInnes, Eric J. L.,Cheng, Yongqiang,Daemen, Luke L.,Rudi?, Svemir,Ramirez-Cuesta, Anibal J.,Tang, Chiu C.,Yang, Sihai
, p. 86 - 93 (2019/12/30)
The efficient production of light olefins from renewable biomass is a vital and challenging target to achieve future sustainable chemical processes. Here we report a hetero-atomic MFI-type zeolite (NbAlS-1), over which aqueous solutions of γ-valerolactone (GVL), obtained from biomass-derived carbohydrates, can be quantitatively converted into butenes with a yield of >99% at ambient pressure under continuous flow conditions. NbAlS-1 incorporates simultaneously niobium(v) and aluminium(iii) centres into the framework and thus has a desirable distribution of Lewis and Br?nsted acid sites with optimal strength. Synchrotron X-ray diffraction and absorption spectroscopy show that there is cooperativity between Nb(v) and the Br?nsted acid sites on the confined adsorption of GVL, whereas the catalytic mechanism for the conversion of the confined GVL into butenes is revealed by in situ inelastic neutron scattering, coupled with modelling. This study offers a prospect for the sustainable production of butene as a platform chemical for the manufacture of renewable materials.
A gradient reduction strategy to produce defects-rich nano-twin Cu particles for targeting activation of carbon-carbon or carbon-oxygen in furfural conversion
An, Zhe,Guo, Shaowei,He, Jing,Ma, Xiaodan,Shu, Xin,Song, Hongyan,Xiang, Xu,Zhang, Jian,Zhu, Yanru
, p. 78 - 86 (2020/06/21)
Complexity of chemical linkages (C-C/C-H/C-O, C=C/C=O, or C-O-H/C-O-C) in biomass-derived molecules makes the selective activation of targeted bonds much more challenging, expecting well-defined catalysts and definite catalytically-active sites. This work demonstrates an effective gradient reduction strategy to control the definite structure of catalytically-active sites, affording defects-rich nano-twin Cu particles. This strategy just involves the reduction (calcination under H2) of CuII-containing layered double hydroxides (LDHs) simply with controlling the reduction gradient (interval time) of CuII species in two chemical micro-environments (CuII-O-CuII and CuII-O-MII/III/IV (M ≠ Cu)) in the brucite-like layer of LDHs. The nano-twin Cu particles efficiently promote the target activation of C-O and C=C in the conversion of furfural to cyclopentanone (CPO). With ~100% furfural conversion, the defects-rich nano-twin Cu particles afford a CPO selectivity of 92%, 50% higher than regular spherical Cu particles. The multi-stepped defect sites, originating from the planar defects, play a decisive role in promoting the CPO selectivity by facilitating the hydro-deoxygenation to C-O of 4-hydroxycyclopentenone (HCP) and hydrogenation to C=C of HCP or cyclopentenone.
Double-metal cyanide as an acid and hydrogenation catalyst for the highly selective ring-rearrangement of biomass-derived furfuryl alcohol to cyclopentenone compounds
Deng, Qiang,Deng, Shuguang,Gao, Rui,Li, Xiang,Lu, Chenxi,Tong, Zhikun,Wang, Jun,Yu, Lian,Zeng, Zheling,Zou, Ji-Jun
, p. 2549 - 2557 (2020/05/28)
Herein, novel green synthetic routes to 4-hydroxy-2-cyclopentenone (HCP) and 2-cyclopentenone (CPE) from biomass-derived furfuryl alcohol via double-metal cyanide catalysis are proposed. For the synthesis of HCP, in comparison to conventional solid acids (i.e., Amberlyst-15), MOFs with coordinatively unsaturated metal ions as pure Lewis acid sites exhibit advantageous catalytic selectivity in the reaction under an N2 atmosphere in a bi-phasic water/n-hexane solvent system. FeZn and FeZn-P result in an HCP yield of 77.4% and 88.2%, respectively. For the CPE synthesis, the reaction conditions are the same as those for HCP, except a mono-phasic water solvent system and H2 atmosphere were employed. In addition to the acid-catalyzed rearrangement reaction, FeZn-DMC exhibits catalytic hydrogenation capability via heterolytic cleavage of the H-H bond over Zn-N frustrated Lewis pairs, and a CPE yield of 61.5% is obtained. The DFT simulation indicates that the acid sites and catalytic acid sites are ascribed to the tri-coordinatively unsaturated Zn2+ site (Zn(N)3) on the catalyst surface. Moreover, the DMC catalyst shows excellent stability and recycling performance. This work not only provides an efficient and green catalytic system for CPE and HCP preparation but also demonstrates the interesting bifunctional catalysis of both acid and hydrogenation catalysis over DMC.
Rediscovering aminal chemistry: Copper(ii) catalysed formation under mild conditions
Afonso, Carlos A. M.,António, Jo?o P. M.,Gomes, Rafael F. A.,Mendon?a, Ricardo,Pereira, Juliana G.
supporting information, p. 7484 - 7490 (2020/11/18)
Aminals, the N,N analogues of acetals, have been thoroughly explored in organic chemistry, with a particular focus on heteroaromatic aldehyde lithiation. Nevertheless, the existing methodologies for their formation typically employ harsh conditions limiting their usefulness. In this work, we present an efficient and mild methodology for the preparation of aminals from aromatic aldehydes, including furanic platforms. These mild conditions allowed ease of access to a plethora of aminals and as such we set out to explore previously unaccessible potential applications. By studying the stability of various aminals, we were able to develop a simple aldehyde protecting group based on a commercial diamine which is deprotected under mind conditions. We developed a protocol for the scavenging of genotoxic aldehydes by taking advantage of our methodology and a diamine resin, as well as early studies on the development of a stimuli-responsive release system using a salycil aldehyde derived aminal. This journal is
Continuous synthesis method of 2-cyclopentene-1-ketone
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Paragraph 0031-0047, (2019/11/20)
The invention provides a continuous synthesis method of 2-cyclopentene-1-ketone. The continuous synthesis method comprises the steps that a continuous reaction device is loaded with a catalyst, then cyclopentene, an oxidizing agent and a solvent are continuously conveyed into the continuous reaction device for an oxidation reaction, and the 2-cyclopentene-1-ketone is continuously discharged. The continuous synthesis method of the 2-cyclopentene-1-ketone has the advantages that in the presence of the catalyst and the solvent, the cyclopentene is used as a starting material, and the cyclopenteneand the oxidizing agent are directly subjected to the oxidation reaction, which can avoid the generation of a large amount of halogen-containing three wastes; the entire continuous synthesis processcan effectively inhibit the occurrence of safety risks during scale-up production in the continuous reaction device; in addition, after the reaction is completed, a product system of the oxidation reaction is simply concentrated to obtain the target product (2-cyclopentene-1-ketone), thereby greatly improving the purity ( up to 98% or above) and separation rate (up to 79%) of the product, and making the scale-up production easy.
