20574-98-5Relevant academic research and scientific papers
TiO2 Photocatalysis in Aromatic "redox Tag"-Guided Intermolecular Formal [2 + 2] Cycloadditions
Okada, Yohei,Maeta, Naoya,Nakayama, Kaii,Kamiya, Hidehiro
, p. 4948 - 4962 (2018)
Since the pioneering work by Macmillan, Yoon, and Stephenson, homogeneous photoredox catalysis has occupied a central place in new reaction development in the field of organic chemistry. While heterogeneous semiconductor photocatalysis has also been studied extensively, it has generally been recognized as a redox option in inorganic chemistry where such "photocatalysis" is most often used to catalyze carbon-carbon bond cleavage and not in organic chemistry where bond formation is usually the focal point. Herein, we demonstrate that titanium dioxide photocatalysis is a powerful redox option to construct carbon-carbon bonds by using intermolecular formal [2 + 2] cycloadditions as models. Synergy between excited electrons and holes generated upon irradiation is expected to promote the overall net redox neutral process. Key for the successful application is the use of a lithium perchlorate/nitromethane electrolyte solution, which exhibits remarkable Lewis acidity to facilitate the reactions of carbon-centered radical cations with carbon nucleophiles. The reaction mechanism is reasonably understood based on both intermolecular and intramolecular single electron transfer regulated by an aromatic "redox tag". Most of the reactions were completed in less than 30 min even in aqueous and/or aerobic conditions without the need for sacrificial reducing or oxidizing substrates generally required for homogeneous photoredox catalysis.
Copper-Catalyzed Intermolecular Enantioselective Radical Oxidative C(sp3)?H/C(sp)?H Cross-Coupling with Rationally Designed Oxazoline-Derived N,N,P(O)-Ligands
Gu, Qiang-Shuai,Guo, Kai-Xin,Li, Zhong-Liang,Liu, Lin,Liu, Xin-Yuan,Tian, Yu,Yang, Chang-Jiang,Ye, Liu
supporting information, p. 26710 - 26717 (2021/11/18)
The intermolecular asymmetric radical oxidative C(sp3)?C(sp) cross-coupling of C(sp3)?H bonds with readily available terminal alkynes is a promising method to forge chiral C(sp3)?C(sp) bonds because of the high atom and step economy, but remains underexplored. Here, we report a copper-catalyzed asymmetric C(sp3)?C(sp) cross-coupling of (hetero)benzylic and (cyclic)allylic C?H bonds with terminal alkynes that occurs with high to excellent enantioselectivity. Critical to the success is the rational design of chiral oxazoline-derived N,N,P(O)-ligands that not only tolerate the strong oxidative conditions which are requisite for intermolecular hydrogen atom abstraction (HAA) processes but also induce the challenging enantiocontrol. Direct access to a range of synthetically useful chiral benzylic alkynes and 1,4-enynes, high site-selectivity among similar C(sp3)?H bonds, and facile synthesis of enantioenriched medicinally relevant compounds make this approach very attractive.
Catalytic δ-hydroxyalkynone rearrangement in the stereoselective total synthesis of centrolobine, engelheptanoxides A and C and analogues
Ahmad, Mohammad N.,Chopra, Sidharth,Fernandes, Rodney A.,Kumar, Praveen
, (2021/08/13)
A catalytic stereoselective total synthesis of centrolobine and engelheptanoxides A and C has been completed via a metal-free catalytic δ-hydroxyalkynone rearrangement to 2,3-dihydro-4H-pyran-4-one and diastereoselective hydrogenation to the all syn-2,4,6-trisubstituted pyran strategy. The onliest required chirality was introduced by Jacobsen kinetic resolution, which further directed the diastereoselective hydrogenation. A first stereoselective synthesis of engelheptanoxide A is also accomplished. The analogues and derivatives of centrolobine and engelheptanoxides prepared were evaluated for antitubercular activity against M. tuberculosis H37Rv ATCC 27294.
Nickel-Catalyzed Negishi-Type Arylation of Trialkylsulfonium Salts
Minami, Hiroko,Nogi, Keisuke,Yorimitsu, Hideki
, p. 1542 - 1546 (2021/09/06)
Negishi-type arylation of trialkylsulfonium salts with arylzinc reagents has been accomplished under nickel catalysis. The use of cyclohexanethiol as an additional ligand was found to be particularly important to promote C-S cleavage. The present reaction accommodates one-pot arylation of dialkyl sulfides by combining with S -methylation with MeOTf. Mechanistic experiments suggest that C-S cleavage would proceed via single-electron transfer (SET) to generate the most stable carbon-centered radical and that the thiolate ligand would promote the C-S cleavage and radical recombination step.
Method for preparing olefin compound under alkaline condition
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Paragraph 0024-0026, (2021/05/29)
The invention relates to a method for preparing an olefin compound under an alkaline condition. The method comprises the following steps: adding a solvent and an alkali catalyst into long-chain alcohol serving as a raw material, introducing sulfuryl fluoride gas, stirring for reaction, and separating and purifying to obtain the olefin compound. The olefin compound has a structural formula shown in the description; and in the formula, R is phenyl, substituted phenyl, heterocyclic aryl, fused ring aryl, substituted fused ring aryl or alkyl. An alkali-promoted alcohol-to-olefin conversion method developed by the invention is mild in reaction condition, simple and convenient to operate and low in instrument and equipment requirements, the long-chain alcohol is used as a reaction raw material, the price is low, the source is wide, and the yield of the prepared olefin compound is high; and the method effectively avoids the influence of acidic conditions on part of groups (acetal, ketal, epoxy and the like), is efficient in reaction and wide in substrate application range, can tolerate most of functional groups, and provides a new path for synthesis of complex olefins.
Electrochemically Enabled, Nickel-Catalyzed Dehydroxylative Cross-Coupling of Alcohols with Aryl Halides
Li, Zijian,Sun, Wenxuan,Wang, Xianxu,Li, Luyang,Zhang, Yong,Li, Chao
supporting information, p. 3536 - 3543 (2021/03/08)
As alcohols are ubiquitous throughout chemical science, this functional group represents a highly attractive starting material for forging new C-C bonds. Here, we demonstrate that the combination of anodic preparation of the alkoxy triphenylphosphonium ion and nickel-catalyzed cathodic reductive cross-coupling provides an efficient method to construct C(sp2)-C(sp3) bonds, in which free alcohols and aryl bromides - both readily available chemicals - can be directly used as coupling partners. This nickel-catalyzed paired electrolysis reaction features a broad substrate scope bearing a wide gamut of functionalities, which was illustrated by the late-stage arylation of several structurally complex natural products and pharmaceuticals.
Access to Trisubstituted Fluoroalkenes by Ruthenium-Catalyzed Cross-Metathesis
Nouaille, Augustin,Pannecoucke, Xavier,Poisson, Thomas,Couve-Bonnaire, Samuel
supporting information, p. 2140 - 2147 (2021/03/06)
Although the olefin metathesis reaction is a well-known and powerful strategy to get alkenes, this reaction remained highly challenging with fluororalkenes, especially the Cross-Metathesis (CM) process. Our thought was to find an easy accessible, convenient, reactive and post-functionalizable source of fluoroalkene, that we found as the methyl 2-fluoroacrylate. We reported herein the efficient ruthenium-catalyzed CM reaction of various terminal and internal alkenes with methyl 2-fluoroacrylate giving access, for the first time, to trisubstituted fluoroalkenes stereoselectively. Unprecedent TON for CM involving fluoroalkene, up to 175, have been obtained and the reaction proved to be tolerant and effective with a large range of olefin partners giving fair to high yields in metathesis products. (Figure presented.).
Mild olefin formationviabio-inspired vitamin B12photocatalysis
Bam, Radha,Pollatos, Alexandros S.,Moser, Austin J.,West, Julian G.
, p. 1736 - 1744 (2021/02/22)
Dehydrohalogenation, or elimination of hydrogen-halide equivalents, remains one of the simplest methods for the installation of the biologically-important olefin functionality. However, this transformation often requires harsh, strongly-basic conditions, rare noble metals, or both, limiting its applicability in the synthesis of complex molecules. Nature has pursued a complementary approach in the novel vitamin B12-dependent photoreceptor CarH, where photolysis of a cobalt-carbon bond leads to selective olefin formation under mild, physiologically-relevant conditions. Herein we report a light-driven B12-based catalytic system that leverages this reactivity to convert alkyl electrophiles to olefins under incredibly mild conditions using only earth abundant elements. Further, this process exhibits a high level of regioselectivity, producing terminal olefins in moderate to excellent yield and exceptional selectivity. Finally, we are able to access a hitherto-unknown transformation, remote elimination, using two cobalt catalysts in tandem to produce subterminal olefins with excellent regioselectivity. Together, we show vitamin B12to be a powerful platform for developing mild olefin-forming reactions.
Controllable Isomerization of Alkenes by Dual Visible-Light-Cobalt Catalysis
Meng, Qing-Yuan,Schirmer, Tobias E.,Katou, Kousuke,K?nig, Burkhard
supporting information, p. 5723 - 5728 (2019/04/03)
We report herein that thermodynamic and kinetic isomerization of alkenes can be accomplished by the combination of visible light with Co catalysis. Utilizing Xantphos as the ligand, the most stable isomers are obtained, while isomerizing terminal alkenes over one position can be selectively controlled by using DPEphos as the ligand. The presence of the donor–acceptor dye 4CzIPN accelerates the reaction further. Transformation of exocyclic alkenes into the corresponding endocyclic products could be efficiently realized by using 4CzIPN and Co(acac)2 in the absence of any additional ligands. Spectroscopic and spectroelectrochemical investigations indicate CoI being involved in the generation of a Co hydride, which subsequently adds to alkenes initiating the isomerization.
Rhenium complex-catalyzed carbon-carbon formation of alcohols and organosilicon compounds
Umeda, Rui,Jikyo, Toshifumi,Toda, Kazuki,Osaka, Issey,Nishiyama, Yutaka
supporting information, p. 1121 - 1124 (2018/02/21)
The coupling reactions of allylic and benzylic alcohols and allyltrimethylsilane are efficiently catalyzed by a rhenium complex to give the corresponding 1,5-dienes and alkenes in moderate to good yields. Similarly, alcohols were coupled with ketene silyl acetals to form the corresponding esters.
