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Kiyoshi Tomioka - One of the best experts on this subject based on the ideXlab platform.
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amidophosphane copper i catalyzed asymmetric conjugate addition of dialkylzinc reagents to racemic 6 substituted cyclohexenones to form 2 5 di and 2 2 5 trisubstituted Cyclohexanones
Chemistry-an Asian Journal, 2008Co-Authors: Khalid B Selim, Takahiro Soeta, Kenichi Yamada, Kiyoshi TomiokaAbstract:The asymmetric conjugate addition of dialkylzinc reagents to racemic 6-substituted cyclohexenones under the catalysis of chiral amidophosphane-copper(I) complexes gave a mixture of nearly equal amounts of the corresponding trans- and cis-disubstituted Cyclohexanones with extremely high catalyst-controlled enantioselectivity. Epimerization with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) led to the conversion of these mixtures into the thermodynamically more stable trans-2,5-disubstituted cyclohexanone as the major product with up to 96% ee in up to 96% yield. The regio- and stereoselective alkylation of the disubstituted cyclohexanone products via the thermodynamically favored enolate gave 2,2,5-trisubstituted Cyclohexanones with a quaternary asymmetric carbon atom in good yield.
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efficient catalytic asymmetric synthesis of trans 5 aryl 2 substituted Cyclohexanones by rhodium catalyzed conjugate arylation of racemic 6 substituted cyclohexenones
Advanced Synthesis & Catalysis, 2006Co-Authors: Qian Chen, Takahiro Soeta, Kenichi Yamada, Masami Kuriyama, Kiyoshi TomiokaAbstract:Catalytic asymmetric conjugate arylation of racemic 6-substituted cyclohexenones with arylboronic acids was catalyzed by 3 mol % of chiral amidophosphane-[RhCl(C2H4)]2 in a 10:1 mixture of 1,4-dioxane and water at 70 °C to afford a nearly 1:1 mixture of trans- and cis-5-aryl-2-substituted Cyclohexanones in high enantioselectivity, which was subsequently epimerized with sodium ethoxide in ethanol to give thermodynamically stable trans-5-aryl-2-substituted Cyclohexanones with 99–97 % ee in high two-step yields.
Guojun Deng - One of the best experts on this subject based on the ideXlab platform.
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synthesis of o arylenediamines through elemental sulfur promoted aerobic dehydrogenative aromatization of Cyclohexanones with arylamines
Organic Letters, 2018Co-Authors: Zhen Wang, Xiangui Chen, Hao Xie, Dahan Wang, Huawen Huang, Guojun DengAbstract:Herein, the first elemental sulfur-promoted aerobic dehydrogenative aromatization of Cyclohexanones is described that provides novel access to synthetically useful o-arylenediamines. This protocol complements previous palladium- and iodine-catalyzed diarylamine formation from Cyclohexanones and anilines.
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Synthesis of o‑Arylenediamines through Elemental Sulfur-Promoted Aerobic Dehydrogenative Aromatization of Cyclohexanones with Arylamines
2018Co-Authors: Zhen Wang, Xiangui Chen, Hao Xie, Dahan Wang, Huawen Huang, Guojun DengAbstract:Herein, the first elemental sulfur-promoted aerobic dehydrogenative aromatization of Cyclohexanones is described that provides novel access to synthetically useful o-arylenediamines. This protocol complements previous palladium- and iodine-catalyzed diarylamine formation from Cyclohexanones and anilines
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efficient pyrido 1 2 a benzimidazole formation from 2 aminopyridines and Cyclohexanones under metal free conditions
Green Chemistry, 2016Co-Authors: Yanjun Xie, Guojun Deng, Huawen Huang, Xingzong Che, Ya ChenAbstract:An efficient procedure for pyrido[1,2-a]benzimidazole preparation from 2-aminopyridines and Cyclohexanones under metal-free conditions is described. Non-aromatic Cyclohexanones were used as the aryl source via a dehydrogenation–aromatization process using molecular oxygen as the green oxidant.
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palladium catalyzed direct arylation of indoles with Cyclohexanones
Organic Letters, 2014Co-Authors: Shanping Chen, Yunfeng Liao, Feng Zhao, Saiwen Liu, Guojun DengAbstract:A novel palladium catalyzed approach to 3-arylindoles was developed from indoles and Cyclohexanones. Various Cyclohexanones acted as aryl sources via an alkylation and dehydrogenation sequence using molecular oxygen as the hydrogen acceptor. This method showed good regioselectivity and afforded 3-arylindoles as the sole products.
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iodine catalyzed efficient 2 arylsulfanylphenol formation from thiols and Cyclohexanones
Green Chemistry, 2013Co-Authors: Yunfeng Liao, Pengcheng Jiang, Shanping Chen, Guojun DengAbstract:A novel method for the formation of 2-arylsulfanylphenols from thiols and Cyclohexanones is described. Iodine was used as an effective catalyst for this kind of transformation. Cyclohexanones were used as a phenol source via a dehydrogenation and tautomerization reaction.
Noritaka Mizuno - One of the best experts on this subject based on the ideXlab platform.
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selective synthesis of primary anilines from nh3 and Cyclohexanones by utilizing preferential adsorption of styrene on the pd nanoparticle surface
Angewandte Chemie, 2019Co-Authors: Yu Koizumi, Xiongjie Jin, Kyoko Nozaki, Noritaka Mizuno, Takafumi Yatabe, Ray Miyazaki, Junya Hasegawa, Kazuya YamaguchiAbstract:Dehydrogenative aromatization is one of the attractive alternative methods for directly synthesizing primary anilines from NH3 and Cyclohexanones. However, the selective synthesis of primary anilines is quite difficult because the desired primary aniline products and the cyclohexanone substrates readily undergo condensation affording the corresponding imines (i.e., N-cyclohexylidene-anilines), followed by hydrogenation to produce N-cyclohexylanilines as the major products. In this study, primary anilines were selectively synthesized in the presence of supported Pd nanoparticle catalysts (e.g., Pd/HAP, HAP=hydroxyapatite, Ca10 (PO4 )6 (OH)2 ) by utilizing competitive adsorption unique to heterogeneous catalysis; in other words, when styrene was used as a hydrogen acceptor, which preferentially adsorbs on the Pd nanoparticle surface in the presence of N-cyclohexylidene-anilines, various structurally diverse primary anilines were selectively synthesized from readily accessible NH3 and Cyclohexanones. The Pd/HAP catalyst was reused several times though its catalytic performance gradually declined.
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selective synthesis of primary anilines from cyclohexanone oximes by the concerted catalysis of a mg al layered double hydroxide supported pd catalyst
Journal of the American Chemical Society, 2017Co-Authors: Xiongjie Jin, Yu Koizumi, Kazuya Yamaguchi, Kyoko Nozaki, Noritaka MizunoAbstract:Although the selective conversion of cyclohexanone oximes to primary anilines would be a good complement to the classical synthetic methods for primary anilines, which utilize arenes as the starting materials, there have been no general and efficient methods for the conversion of cyclohexanone oximes to primary anilines until now. In this study, we have successfully realized the efficient conversion of cyclohexanone oximes to primary anilines by utilizing a Mg-Al layered double hydroxide supported Pd catalyst (Pd(OH)x/LDH) under ligand-, additive-, and hydrogen-acceptor-free conditions. The substrate scope was very broad with respect to both cyclohexanone oximes and cyclohexenone oximes, which gave the corresponding primary anilines in high yields with high selectivities (17 examples, 75% to >99% yields). The reaction could be scaled up (gram-scale) with a reduced amount of the catalyst (0.2 mol %). Furthermore, the one-pot synthesis of primary anilines directly from Cyclohexanones and hydroxylamine was also successful (five examples, 66-99% yields). The catalysis was intrinsically heterogeneous, and the catalyst could be reused for the conversion of cyclohexanone oxime to aniline at least five times with keeping its high catalytic performance. Kinetic studies and several control experiments showed that the high activity and selectivity of the present catalyst system were attributed to the concerted catalysis of the basic LDH support and the active Pd species on LDH. The present transformation of cyclohexanone oximes to primary anilines proceeds through a dehydration/dehydrogenation sequence, and herein the plausible reaction mechanism is proposed on the basis of several pieces of experimental evidence.
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Selective Synthesis of Primary Anilines from Cyclohexanone Oximes by the Concerted Catalysis of a Mg–Al Layered Double Hydroxide Supported Pd Catalyst
2017Co-Authors: Xiongjie Jin, Yu Koizumi, Kazuya Yamaguchi, Kyoko Nozaki, Noritaka MizunoAbstract:Although the selective conversion of cyclohexanone oximes to primary anilines would be a good complement to the classical synthetic methods for primary anilines, which utilize arenes as the starting materials, there have been no general and efficient methods for the conversion of cyclohexanone oximes to primary anilines until now. In this study, we have successfully realized the efficient conversion of cyclohexanone oximes to primary anilines by utilizing a Mg–Al layered double hydroxide supported Pd catalyst (Pd(OH)x/LDH) under ligand-, additive-, and hydrogen-acceptor-free conditions. The substrate scope was very broad with respect to both cyclohexanone oximes and cyclohexenone oximes, which gave the corresponding primary anilines in high yields with high selectivities (17 examples, 75% to >99% yields). The reaction could be scaled up (gram-scale) with a reduced amount of the catalyst (0.2 mol %). Furthermore, the one-pot synthesis of primary anilines directly from Cyclohexanones and hydroxylamine was also successful (five examples, 66–99% yields). The catalysis was intrinsically heterogeneous, and the catalyst could be reused for the conversion of cyclohexanone oxime to aniline at least five times with keeping its high catalytic performance. Kinetic studies and several control experiments showed that the high activity and selectivity of the present catalyst system were attributed to the concerted catalysis of the basic LDH support and the active Pd species on LDH. The present transformation of cyclohexanone oximes to primary anilines proceeds through a dehydration/dehydrogenation sequence, and herein the plausible reaction mechanism is proposed on the basis of several pieces of experimental evidence
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au pd alloy nanoparticles supported on layered double hydroxide for heterogeneously catalyzed aerobic oxidative dehydrogenation of cyclohexanols and Cyclohexanones to phenols
Chemical Science, 2016Co-Authors: Xiongjie Jin, Kazuya Yamaguchi, Kento Taniguchi, Noritaka MizunoAbstract:Phenol, an important industrial chemical, is widely produced using the well-developed cumene process. However, demand for the development of a novel alternative method for synthesizing phenol from benzene has been increasing. Herein, we report a novel system for the synthesis of phenols through aerobic oxidative dehydrogenation of cyclohexanols and Cyclohexanones, including ketone–alcohol (KA) oil, catalyzed by Mg–Al-layered double hydroxide (LDH)-supported Au–Pd alloy nanoparticles (Au–Pd/LDH). Alloying of Au and Pd and basicity of LDH are key factors in achieving the present transformation. Although monometallic Au/LDH, Pd/LDH, and their physical mixture showed almost no catalytic activity, Au–Pd/LDH exhibited markedly high catalytic activity for the dehydrogenative phenol production. Mechanistic studies showed that β-H elimination from Pd-enolate species is accelerated by Au species, likely via electronic ligand effects. Moreover, the effect of supports was critical; despite the high catalytic performance of Au–Pd/LDH, Au–Pd bimetallic nanoparticles supported on Al2O3, TiO2, MgO, and CeO2 were ineffective. Thus, the basicity of LDH plays a deterministic role in the present dehydrogenation possibly through its assistance in the deprotonation steps. The synthetic scope of the Au–Pd/LDH-catalyzed system was very broad; various substituted cyclohexanols and Cyclohexanones were efficiently converted into the corresponding phenols, and N-substituted anilines were synthesized from Cyclohexanones and amines. In addition, the observed catalysis was truly heterogeneous, and Au–Pd/LDH could be reused without substantial loss of its high performance. The present transformation is scalable, utilizes O2 in air as the terminal oxidant, and generates water as the only by-product, highlighting the potential practical utility and environmentally benign nature of the present transformation. Dehydrogenative aromatization of cyclohexanols proceeds through (1) oxidation of cyclohexanols to Cyclohexanones; (2) dehydrogenation of Cyclohexanones to cyclohexenones; and (3) disproportionation of cyclohexenones to afford the desired phenols. In the present Au–Pd/LDH-catalyzed transformation, the oxidation of the Pd–H species is included in the rate-determining step.
Shannon S Stahl - One of the best experts on this subject based on the ideXlab platform.
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aerobic dehydrogenation of cyclohexanone to cyclohexenone catalyzed by pd dmso 2 tfa 2 evidence for ligand controlled chemoselectivity
Journal of the American Chemical Society, 2013Co-Authors: Tianning Diao, Shannon S StahlAbstract:The dehydrogenation of Cyclohexanones affords cyclohexenones or phenols via removal of 1 or 2 equiv of H2, respectively. We recently reported several PdII catalyst systems that effect aerobic dehydrogenation of Cyclohexanones with different product selectivities. Pd(DMSO)2(TFA)2 is unique in its high chemoselectivity for the conversion of Cyclohexanones to cyclohexenones, without promoting subsequent dehydrogenation of cyclohexenones to phenols. Kinetic and mechanistic studies of these reactions reveal the key role of the dimethylsulfoxide (DMSO) ligand in controlling this chemoselectivity. DMSO has minimal kinetic influence on the rate of Pd(TFA)2-catalyzed dehydrogenation of cyclohexanone to cyclohexenone, while it strongly inhibits the second dehydrogenation step, conversion of cyclohexenone to phenol. These contrasting kinetic effects of DMSO provide the basis for chemoselective formation of cyclohexenones.
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aerobic dehydrogenation of cyclohexanone to phenol catalyzed by pd tfa 2 2 dimethylaminopyridine evidence for the role of pd nanoparticles
Journal of the American Chemical Society, 2013Co-Authors: Doris Pun, Tianning Diao, Shannon S StahlAbstract:We have carried out a mechanistic investigation of aerobic dehydrogenation of Cyclohexanones and cyclohexenones to phenols with a Pd(TFA)2/2-dimethylaminopyridine catalyst system. Numerous experimental methods, including kinetic studies, filtration tests, Hg poisoning experiments, transmission electron microscopy, and dynamic light scattering, provide compelling evidence that the initial PdII catalyst mediates the first dehydrogenation of cyclohexanone to cyclohexenone, after which it evolves into soluble Pd nanoparticles that retain catalytic activity. This nanoparticle formation and stabilization is facilitated by each of the components in the catalytic reaction, including the ligand, TsOH, DMSO, substrate, and cyclohexenone intermediate.
Jon D Stewart - One of the best experts on this subject based on the ideXlab platform.
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assessing the substrate selectivities and enantioselectivities of eight novel baeyer villiger monooxygenases toward alkyl substituted Cyclohexanones
Journal of Organic Chemistry, 2004Co-Authors: Brian Kyte, Pierre Rouviere, Qiong Cheng, Jon D StewartAbstract:Genes encoding eight Baeyer−Villiger monooxygenases have recently been cloned from bacteria inhabiting a wastewater treatment plant. We have carried out a systematic investigation in which each newly cloned enzyme, as well as the cyclohexanone monooxygenase from Acinetobacter sp. NCIB 9871, was used to oxidize 15 different alkyl-substituted Cyclohexanones. The panel of substrates included equal numbers of 2-, 3-, and 4-alkyl-substituted compounds to probe each enzyme's stereoselectivity toward a homologous series of synthetically important compounds. For all 4-alkyl-substituted Cyclohexanones tested, enzymes were discovered that afforded each of the corresponding (S)-lactones in ≥98% ee. This was also true for the 2-alkyl-substituted Cyclohexanones examined. The situation was more complex for 3-akyl-substituted Cyclohexanones. In a few cases, single Baeyer−Villiger monooxygenases possessed both high regio- and enantioselectivities toward these compounds. More commonly, however, they showed only one type o...
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asymmetric baeyer villiger oxidations of 4 mono and 4 4 disubstituted Cyclohexanones by whole cells of engineered escherichia coli
Journal of Organic Chemistry, 2001Co-Authors: Marko D Mihovilovic, Margaret M Kayser, Gang Chen, Shaozhao Wang, Brian Kyte, Fernande D Rochon, Jon D StewartAbstract:Whole cells of an Escherichia coli strain that overexpresses Acinetobacter sp. NCIB 9871 cyclohexanone monooxygenase have been used for the Baeyer−Villiger oxidations of a variety of 4-mono- and 4,4-disubstituted Cyclohexanones. In cases where comparisons were possible, this new biocatalytic reagent provided lactones with chemical yields and optical purities that were comparable to those obtained from the purified enzyme or a strain of bakers' yeast that expresses the same enzyme. The efficient production of cyclohexanone monooxygenase in the E. coli expression system (ca. 30% of total soluble protein) allowed these oxidations to reach completion in approximately half the time required for the engineered bakers' yeast strain. Surprisingly, 4,4-disubstituted Cyclohexanones were also accepted by the enzyme, and the enantioselectivities of these oxidations could be rationalized by considering the conformational energies of bound substrates along with the enzyme's intrinsic enantioselectivity. The enzyme expr...
