Review
Chemistry, Multidisciplinary
Fujie Tanaka
Summary: This article discusses catalysts and catalyst systems that use amino acids, primary, secondary, and/or tertiary amines as key catalytic functional groups to accelerate chemical transformations. It also explores strategies and methods that utilize amine derivatives as catalysts. The understanding of dynamics and kinetic controls in amine-catalyzed reactions has enabled the synthesis of complex molecules in stereocontrolled manners.
Review
Chemistry, Applied
Hongxiang Li, Honglei Liu, Hongchao Guo
Summary: Quaternary phosphonium salts are extensively used as Lewis acid organocatalysts in organic synthesis, particularly for Mannich, Strecker, and Friedel-Crafts reactions, allowing the construction of structurally diverse and synthetically useful architectures.
ADVANCED SYNTHESIS & CATALYSIS
(2021)
Article
Biochemistry & Molecular Biology
Anna S. Tovmasyan, Anna F. Mkrtchyan, Hamlet N. Khachatryan, Mary V. Hayrapetyan, Robert M. Hakobyan, Artavazd S. Poghosyan, Avetis H. Tsaturyan, Ela V. Minasyan, Victor I. Maleev, Vladimir A. Larionov, Armen G. Ayvazyan, Norio Shibata, Giovanni N. Roviello, Ashot S. Saghyan
Summary: A new family of Cu(II) and Ni(II) salen complexes was synthesized and characterized. These complexes were evaluated for their catalytic activity in the C-alpha-alkylation reaction of Schiff bases. It was found that introducing a chlorine atom into the phenyl ring of the substrate increased both the chemical yield and asymmetric induction. The highest enantiomeric excess was achieved using a Cu(II) salen complex based on (S,S)-cyclohexanediamine and salicylaldehyde at -20 degrees C. Bulky substituents in the ligand led to a decrease in both the enantioselectivity and chemical yield, with complete loss of stereoselectivity achieved with certain substituents at positions 3 and 5 of the phenyl ring.
Article
Chemistry, Multidisciplinary
Rosa Lopez, Claudio Palomo
Summary: N,N-Diacylaminals are flexible molecular scaffolds commonly used as amide surrogates in peptidomimetics. Recently, their singularity as an N-acyl imine equivalent and hydrogen-bond donor has led to new synthetic opportunities, particularly in the field of asymmetric catalysis. This concept article highlights the diverse synthetic potential of N,N-Diacylaminals and provides the necessary elements for further developments.
CHEMISTRY-A EUROPEAN JOURNAL
(2021)
Review
Chemistry, Applied
Gabriele Lupidi, Alessandro Palmieri, Marino Petrini
Summary: N-Activated ketimines are characterized by electron-withdrawing groups linked to the nitrogen atom, enhancing the electrophilic character and allowing addition reactions with weak nucleophiles. The presence of oxygen atoms in these groups is crucial for asymmetric catalytic reactions. This review summarizes the literature on the synthesis of optically active alpha-substituted amino derivatives using open-chain N-activated ketimines.
ADVANCED SYNTHESIS & CATALYSIS
(2021)
Article
Chemistry, Applied
Andreas Eitzinger, Jan Otevrel, Victoria Haider, Antonio Macchia, Antonio Massa, Kirill Faust, Bernhard Spingler, Albrecht Berkessel, Mario Waser
Summary: In this study, chiral 3,3-disubstituted isoindolinones were synthesized using ammonium salt catalysis, yielding a variety of differently substituted CF3S- and RS-derivatives with high enantioselectivities. Additionally, a racemic synthesis of F-containing products was achieved for the first time, producing a stable alpha-F-alpha-amino acid derivative.
ADVANCED SYNTHESIS & CATALYSIS
(2021)
Review
Chemistry, Organic
Suman K. Saha, Anupriya Bera, Soniya Singh, Nirmal K. Rana
Summary: Nitrogen-containing heterocyclic compounds have been extensively studied for their significant applications in synthetic organic chemistry, agrochemicals, and pharmaceuticals. alpha,beta-Unsaturated imines or conjugated imines have been found to react with a versatile family of compounds, leading to the synthesis of important cyclic and acyclic products. This review highlights the recent advances in enantioselective reactions of alpha,beta-unsaturated imines and their synthetic methodologies for synthesizing nitrogen-containing heterocycles containing four to six-membered rings. Additionally, the synthesis of rarely found seven, eight, and nine-membered nitrogen-containing heterocycles is also discussed.
EUROPEAN JOURNAL OF ORGANIC CHEMISTRY
(2023)
Review
Chemistry, Organic
Wei Wen, Qi-Xiang Guo
Summary: This article summarizes the recent advances in the application of chiral aldehyde catalysis in asymmetric reactions and prospects its future development.
SYNTHESIS-STUTTGART
(2023)
Article
Chemistry, Multidisciplinary
Zhibin Guo, Daehyun Oh, Min Sagong, Jewon Yang, Geumwoo Lee, Hyeung-geun Park
Summary: An efficient method for synthesizing chiral malonates was established using enantioselective phase transfer catalysis. The a-alkylation reaction of 2,2-diphenylethyl tert-butyl a-methylmalonates with (S,S)-3,4,5-trifluorophenyl-NAS bromide as a phase-transfer catalyst successfully yielded corresponding a-methyl-a-alkylmalonates. These compounds are versatile chiral building blocks with a quaternary carbon center, obtained in high chemical yields (up to 99%) and excellent enantioselectivities (up to 98% ee). Selective hydrolysis of a,a-dialkylmalonates to the corresponding chiral malonic monoacids was achieved using basic (KOH/MeOH) and acidic conditions (TFA/CH2Cl2), demonstrating the practicality of the method.
FRONTIERS IN CHEMISTRY
(2023)
Article
Chemistry, Multidisciplinary
Sei Murayama, Zhurong Li, Huatai Liang, Yan Liu, Hiroshi Naka, Keiji Maruoka
Summary: Site-specifically deuterated organocatalysts exhibit enhanced reactivity compared to non-deuterated analogs in the asymmetric catalytic alkylation of amino acid derivatives. The stability of phase-transfer catalysts can be improved by site-specific deuteration, with a significant secondary kinetic isotope effect observed for tetradeuterated catalysts. These findings suggest that catalyst deuteration is a promising strategy to enhance the stability and performance of organocatalysts.
CHEMISTRY-A EUROPEAN JOURNAL
(2023)
Article
Chemistry, Organic
Ken Okuno, Takumi Nakamura, Seiji Shirakawa
Summary: This study reports the synthesis and asymmetric catalysis of chiral bifunctional selenides and selenonium salts, which promote asymmetric halocyclizations and phase-transfer conjugate additions.
ASIAN JOURNAL OF ORGANIC CHEMISTRY
(2021)
Article
Biochemistry & Molecular Biology
Zsuzsanna Feher, Dora Richter, Sandor Nagy, Peter Bagi, Zsolt Rapi, Andras Simon, Laszlo Drahos, Peter Huszthy, Peter Bako, Jozsef Kupai
Summary: This study synthesized six new phase-transfer organocatalysts with different chiral units and crown ethers of varying sizes to catalyze alpha-alkylation and Michael addition reactions, yielding alpha,alpha-disubstituted malonic ester derivatives with excellent yields up to 98%.
Article
Chemistry, Organic
Apoorva Malik, Pragati R. Sharma, Rakesh K. Sharma
Summary: We report a class of quaternary ammonium Cinchona-functionalized crown ether-strapped calix[4]-arene phase-transfer catalysts for the efficient enantioselective alpha-alkylation of glycine imines. The catalyst exhibits excellent catalytic performance at 0.1 mol % catalytic loading, affording the desired alpha-alkylated glycinates with 98% yield and 99.9% ee. The catalyst could be recovered and recycled up to 30 test cycles without a significant drop in activity.
JOURNAL OF ORGANIC CHEMISTRY
(2023)
Review
Chemistry, Organic
Domenico C. M. Albanese, Michele Penso
Summary: This article highlights the efficacy of phase transfer catalysis (PTC) in performing reactions on both laboratory and industrial scales, with significant cost savings and process improvements. It discusses recent advances in stereoselective reactions using chiral, non-racemic quaternary ammonium salts, the use of bulky, chiral phosphate anions paired with achiral cations to generate lipophilic ion pairs, and the application of hydrogen bond interactions in asymmetric nucleophilic substitutions under PTC conditions.
EUROPEAN JOURNAL OF ORGANIC CHEMISTRY
(2023)
Article
Chemistry, Organic
Feng Jiang, Tengfei Meng, Ying Zhou, Zhenying Xiong, Yupei Zhao, Wengang Guo
Summary: We report an enantio- and diastereodivergent synthesis of enantioenriched fluorenes with broad substrate scope and high enantioselectivity (up to 99% ee) under low catalyst loading (0.1 mol %). The success of this method lies in the pseudo-diastereodivergent desymmetrization of stereoisomers of meso-epoxides enabled by the same organocatalyst. Furthermore, some of the chiral fluorenes obtained exhibit high fluorescence quantum yields (up to 76.6%), as evidenced by photophysical properties studies.
Article
Chemistry, Organic
Tomoaki Inukai, Taichi Kano, Keiji Maruoka
Summary: An asymmetric synthesis of alpha-aryl-alpha-hydroxy-delta-lactams via phase-transfer-catalyzed hydroxylation with molecular oxygen is described. High yields and high enantioselectivities were achieved using 2,2-diarylvinyl group as an achiral auxiliary, facilitating access to alpha-aryl-alpha-hydroxy-delta-lactam derivatives containing a chiral quaternary center.
Article
Chemistry, Organic
Chihiro Homma, Masahiro Yamanaka, Taichi Kano, Keiji Maruoka
Summary: A facile and practical synthesis of alkynyl Z-ketimines has been developed, serving as a synthetic equivalent of alkyl ketimines. The obtained alkynyl Z-ketimines have been successfully utilized in enantioselective Mannich reaction and conjugate addition catalyzed by a chiral amine with an acid functionality.
Article
Chemistry, Organic
Yoshiaki Maeda, Suguru Hamada, Yusuke Aota, Kazuya Otsubo, Taichi Kano, Keiji Maruoka
Summary: In this study, we demonstrated an asymmetric synthesis of chiral sulfoximines through a stereospecific S-alkylation of readily accessible chiral sulfinamides under practical conditions. The identification of the intermediate structure in our previously reported S-alkylation by X-ray crystallographic analysis was crucial to establish the practical conditions.
JOURNAL OF ORGANIC CHEMISTRY
(2022)
Article
Chemistry, Organic
Aika Takeshima, Taichi Kano
Summary: A novel amine catalyst - phenylcyclopropane-based amine catalyst - has been designed, which possesses a similar chiral environment to that of binaphthyl-based amine catalysts and exhibits unique chemo- and stereoselectivity in several asymmetric reactions.
Article
Chemistry, Multidisciplinary
Aika Takeshima, Taichi Kano
Summary: A novel method for synthesizing 1,4-dicarbonyl compounds is described, involving the generation of zinc enolates from alpha,alpha-dibromoketones through a diethylzinc-mediated halogen-metal exchange, followed by their reaction with alpha-bromocarbonyl compounds. This cross-coupling reaction enables the selective formation of zinc enolates from alpha,alpha-dibromoketones in the presence of alpha-bromocarbonyl compounds, leading to the synthesis of 1,4-dicarbonyl compounds. Chiral 1,4-dicarbonyl compounds can be obtained through enantioselective bromination of aldehydes and subsequent cross-coupling reaction with chiral alpha-bromoaldehydes and alpha,alpha-dibromoacetophenones.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Multidisciplinary
Saori Tsuzuki, Taichi Kano
Summary: In this study, an efficient method for preparing chiral sulfimides from easily available enantioenriched sulfinamides was reported. The key step involves a stereospecific oxygen-selective alkylation of enantioenriched sulfinamides using isopropyl iodide, K2CO3, and DMPU. The resulting chiral sulfinimidate esters are transformed to chiral sulfimides through nucleophilic addition of Grignard reagents under simple conditions. This method allows access to enantioenriched diaryl or dialkyl sulfimides bearing two similar carbon substituents, which are difficult to synthesize using previous methods.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Letter
Chemistry, Organic
Kento Yasumoto, Noritaka Kunitomo, Taichi Kano
Summary: The Cu-catalyzed asymmetric conjugate addition of trialkenylboroxines to enone diesters is described. This operationally simple and scalable reaction proceeds at room temperature and tolerates a wide range of substrates. The practical utility of this method is demonstrated through the formal synthesis of (+)-methylenolactocin. Mechanistic studies reveal the synergistic action of two different catalytic species.
Article
Chemistry, Organic
Ryoga Hikawa, Mio Shimogaki, Taichi Kano
Summary: Novel threonine-derived amino sulfonamide organocatalysts were developed and successfully applied to asymmetric aldol reactions. The reactions produced anti-aldol adducts with high diastereo- and enantioselectivity when catalyzed by threonine-derived tosylamide, and syn-aldol adducts were obtained when using threonine-derived triflamide catalyst in reactions between alpha-siloxyacetone and aromatic aldehydes. In both cases, a significant improvement in diastereoselectivity was observed compared to threonine-derived carboxylic acid catalyst.
ASIAN JOURNAL OF ORGANIC CHEMISTRY
(2023)
Article
Chemistry, Organic
Saori Tsuzuki, Taichi Kano
Summary: A metal- and additive-free reaction for the transsulfinamidation of N-unsubstituted sulfinamides and N-pivaloyl-protected sulfinamides with various amines is reported. The reaction proceeds by simply heating and provides both N-monosubstituted and N,N-disubstituted sulfinamides in good yields. Preliminary experiments also show that alcohols can be used as nucleophiles instead of amines, giving sulfinate esters.
Article
Chemistry, Organic
Yuki Uwaso, Naoki Yokoyama, Taichi Kano
Summary: Novel axially chiral biphenyl-based amine catalysts were synthesized from dibromopyrenes, and these chiral amines proved to be effective catalysts for asymmetric reactions through enamine intermediates.
ORGANIC & BIOMOLECULAR CHEMISTRY
(2023)
Article
Chemistry, Multidisciplinary
Ryoga Hikawa, Mio Shimogaki, Taichi Kano
Summary: Three contiguous stereocenters were formed through an amino acid-catalyzed asymmetric aldol reaction between alpha-siloxyketones and racemizable alpha-haloaldehydes via dynamic kinetic resolution. The highly functionalized products can also be synthesized in a one-pot catalytic asymmetric manner by alpha-bromination of simple aldehydes followed by the asymmetric aldol reaction.
CHEMICAL COMMUNICATIONS
(2023)
Article
Chemistry, Multidisciplinary
Tino P. Golub, Taichi Kano, Keiji Maruoka, Christian Merten
Summary: We present a VCD spectroscopic characterization of a chiral catalyst and show that the VCD spectra of in situ generated enamine and ex situ prepared iminium ion are different. This study highlights the potential of VCD spectroscopy in distinguishing stable intermediates and determining the dominant conformers in solution.
CHEMICAL COMMUNICATIONS
(2022)
Review
Chemistry, Organic
Chihiro Homma, Taichi Kano
Summary: Binaphthyl-based amine catalysts exhibit unique reactivity and stereoselectivity in asymmetric reactions, but are rarely used due to their synthetic inefficiency. Chiral secondary amine catalysts based on a phenylcyclopropane scaffold have been developed and show high catalytic activity in several asymmetric reactions.
JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN
(2022)
Article
Chemistry, Multidisciplinary
Saori Tsuzuki, Shunya Sakurai, Akira Matsumoto, Taichi Kano, Keiji Maruoka
Summary: This study describes a Ni-catalyzed direct C-H alkylation of N-quinolylbenzamides using alkylsilyl peroxides as alkyl-radical precursors. The reaction forms a new C(sp(3))-C(sp(2)) bond via selective cleavage of both C(sp(3))-C(sp(3)) and C(sp(2))-H bonds. Due to the structural diversity of alkylsilyl peroxides, a wide range of alkyl chains including functional groups and complex structures can be introduced at the ortho-position of readily available N-quinolylbenzamide derivatives.
CHEMICAL COMMUNICATIONS
(2021)
Article
Chemistry, Multidisciplinary
Chihiro Homma, Taichi Kano, Keiji Maruoka
Summary: A bifunctional amino sulfonamide-catalyzed asymmetric conjugate addition of aldehydes to alkenyl alkynyl ketimines has been developed, yielding the desired conjugate adducts with high chemo-, diastereo- and enantioselectivity.
CHEMICAL COMMUNICATIONS
(2021)
