Article
Chemistry, Multidisciplinary
Jia-Bin Pan, Zhi-Chun Yang, Xuan-Ge Zhang, Mao-Lin Li, Qi-Lin Zhou
Summary: Here, we present a method for enantioselective phosphoric acid catalyzed amination of ketenes generated from α-aryl-α-diazoketones. Mechanistic studies elucidated the reaction pathway and explained how the catalyst expedited the transformation and controlled the enantioselectivity.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Multidisciplinary
Zan Yang, Xun Zhang, Yu Jiang, Qiang Ma, Saihu Liao
Summary: The properties of poly(vinyl ether)s depend significantly on their tacticity, with considerable efforts focused on developing stereoselective cationic polymerization methods for isotactic PVEs. Current methods using metal-based Lewis acids have limitations on catalyst loading and monomer scope. A metal-free stereoselective cationic polymerization of vinyl ethers has been introduced using chiral confined Bronsted acids, offering advantages such as high efficiency, high stereoselectivity, and simplicity in operation.
SCIENCE CHINA-CHEMISTRY
(2022)
Article
Chemistry, Organic
Paul Zebrowski, Uwe Monkowius, Mario Waser
Summary: We report a two-step approach for the enantioselective synthesis of novel chiral δ-lactams. The protocol involves an asymmetric α-allylation of activated aryl esters followed by an acid-mediated lactam formation. The method provides highly enantioselective and reasonably high-yielding products, which can be further utilized via transformations of the exocyclic double bond.
EUROPEAN JOURNAL OF ORGANIC CHEMISTRY
(2023)
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.
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
Lotte Stockhammer, Maximilian Radetzky, Syeda Sadia Khatoon, Matthias Bechmann, Mario Waser
Summary: A two-step protocol for the asymmetric synthesis of novel chiral benzofused ε-lactones starting from O-protected hydroxymethyl-para-quinone methides and activated aryl esters is reported. The use of chiral isothiourea Lewis base catalysts allows the obtaining of a broad variety of differently substituted products with high levels of enantioselectivities.
EUROPEAN JOURNAL OF ORGANIC CHEMISTRY
(2023)
Article
Chemistry, Multidisciplinary
Jia-Bin Pan, Xuan-Ge Zhang, Yi-Fan Shi, Ai-Cui Han, Yu-Jia Chen, Jing Ouyang, Mao-Lin Li, Qi-Lin Zhou
Summary: We report the discovery of high-pK(a) Bronsted acid catalysts that enable the asymmetric transformation of free carbenes into chiral alpha-amino acid derivatives by insertion into N-H bonds of amines. Under visible light irradiation, diazo compounds generate high-energy free carbenes that react with amines to form free ylide intermediates. The newly designed high-pK(a) Bronsted acids, chiral spiro phosphamides, facilitate the proton transfer of ylides to afford the products. Computational and kinetic studies provide insights into the rational design of proton-transfer catalysts and the mechanisms underlying their acceleration and stereocontrol in this transformation.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Organic
Mikhail Il'in, Alexandra A. Sysoeva, Alexander S. Novikov, Dmitrii S. Bolotin
Summary: Dibenziodolium and diphenyliodonium triflates have been found to exhibit high catalytic activity in a multicomponent reaction. The study also reveals that the hydrogen atoms adjacent to the iodine atom play a dual role in forming noncovalent bonds with the substrate and increasing the electrostatic potential at the iodine atom. The higher catalytic activity of Dibenziodolium triflate can be explained by the additional energy required for the rotation of the phenyl ring in the diphenyliodonium cation during substrate ligation.
JOURNAL OF ORGANIC CHEMISTRY
(2022)
Article
Chemistry, Applied
Ken Okuno, Bun Chan, Seiji Shirakawa
Summary: Catalytic kinetic resolution is a reliable method for enantioselective synthesis of chiral molecules. However, it is challenging to perform kinetic resolution on racemic compounds with similar substituents at a chiral center. In this study, a kinetic resolution of a-allyl-a-propargyl carboxylic acids was achieved using a chiral bifunctional sulfide catalyst. The utility of the resulting optically active compounds was also demonstrated.
ADVANCED SYNTHESIS & CATALYSIS
(2023)
Article
Chemistry, Multidisciplinary
Peng-Fei Chen, Bo Zhou, Peng Wu, Binju Wang, Long-Wu Ye
Summary: A novel Brønsted acid catalyzed intramolecular hydroalkoxylation/Claisen rearrangement is described for the synthesis of valuable spirolactams from readily available ynamides with good yields, diastereoselectivities, and broad substrate scope. An unexpected dearomatization of nonactivated arenes and heteroaromatic compounds occurs in this reaction. Furthermore, an asymmetric version of this reaction was achieved through efficient kinetic resolution by chiral phosphoric acid catalysis, with theoretical calculations showing a preference for the [3,3]-rearrangement over the [1,3]-rearrangement.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2021)
Article
Chemistry, Multidisciplinary
Avene C. Colgan, Rupert S. J. Proctor, David C. Gibson, Padon Chuentragool, Antti S. K. Lahdenpera, Kristaps Ermanis, Robert J. Phipps
Summary: This study reports a significant advancement in the catalytic enantioselective Minisci reaction, allowing the use of α-hydroxy radical coupling partners to obtain valuable enantioenriched secondary alcohol products. The approach is highly regioselective as well as highly enantioselective.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Chemistry, Multidisciplinary
Andreas Schneider, Philipp Jegl, Bernhard Hauer
Summary: Cascade reactions provide a cutting-edge strategy for assembling complex structural scaffolds efficiently from naturally available precursors. The research introduced in this report demonstrates a method for controlling cationic cyclization cascades through designed hydrogen bonding, leading to directed cyclizations with high selectivity and yields. This approach offers a more efficient and selective way to access natural compounds such as apocarotenoids, value-added flavors, and fragrances.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2021)
Article
Chemistry, Organic
Marina Perez-Palau, Nil Sanosa, Pedro Romea, Felix Urpi, Rosa Lopez, Enrique Gomez-Bengoa, Merce Font-Bardia
Summary: A new stereoselective alkylation method has been developed using titanium(IV) enolates of chiral N-acyl oxazolidinones with tert-butyl peresters from Ca-branched aliphatic carboxylic acids. The reaction proceeds through the decarboxylation of peresters and formation of alkyl radicals, resulting in alkylated adducts with excellent diastereoselectivity. Theoretical calculations explain the observed reactivity and outstanding stereocontrol, with the resulting compounds easily converted into ligands for asymmetric and catalytic transformations.
Article
Chemistry, Multidisciplinary
Ze-Shu Wang, Lu-Jing Zhu, Cui-Ting Li, Bin-Yang Liu, Xin Hong, Long-Wu Ye
Summary: In recent years, there has been significant attention on the asymmetric catalysis of ynamides, with most reactions focused on central chirality. However, the synthesis of axially chiral compounds from ynamides has been limited to noble-metal catalysis. This study presents a metal-free protocol for the construction of axially chiral N-heterocycles from ynamides using chiral Bronsted acid-catalyzed 5-endo-dig cyclization. The method allows for the practical and atom-economical synthesis of valuable N-arylindoles with excellent enantioselectivities, and the resulting axially chiral N-arylindole skeletons can be employed in asymmetric catalysis.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Chemistry, Multidisciplinary
Nobuya Tsuji, Pavel Sidorov, Chendan Zhu, Yuuya Nagata, Timur Gimadiev, Alexandre Varnek, Benjamin List
Summary: Catalyst optimization processes often rely on qualitative assumptions of chemists based on screening data, while machine learning models using molecular properties or calculated 3D structures are time-consuming and costly. This study proposes a machine learning model based on fragment descriptors, which are fine-tuned for asymmetric catalysis and result in robust and efficient virtual screening. Through theoretical design and experimental validation, new catalysts with higher selectivities in a challenging synthesis were developed using only moderately selective training data.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Organic
Hidenori Matsuyama, Xuan Zhang, Masahiro Terada, Tienan Jin
Summary: A versatile method for synthesizing alkylidene fluorenes and their heteroarene derivatives has been successfully developed by using a Pd(II)-catalyzed direct C-H/C-H coupling of o-alkenyl biaryls. Under aerobic oxidation conditions, the use of Pd(OAc)2 catalyst produces alkylidene fluorenes with various functional groups and diverse polycyclic systems. These resulting products can be utilized as versatile synthetic building blocks for constructing structurally diverse polycyclic arenes and heteroarenes.
Article
Chemistry, Multidisciplinary
Saikat Das, Azusa Kondoh, Masahiro Terada
Summary: The direct use of cyanohydrin ether derivatives as less acidic pronucleophiles was achieved for the first time in the catalytic enantioselective Michael addition reaction under transition metal free conditions. Chiral bis(guanidino)iminophosphoranes as the higher order organosuperbase facilitated the intended catalytic Michael addition to enones, giving rise to the corresponding products in high yields with moderate to high diastereo- and enantioselectivities in most cases. Further elaboration of the corresponding enantioenriched product was conducted by derivatization into a lactam derivative through hydrolysis followed by cyclo-condensation.
Review
Chemistry, Organic
Azusa Kondoh, Masahiro Terada
Summary: The [1,2]-phospha-Brook rearrangement involves the migration of a dialkoxyphosphoryl moiety to generate an alpha-oxygenated carbanion. The precursor for this rearrangement can be easily obtained through deprotonation or addition reactions under the influence of a Bronsted base. This review article summarizes recent developments in Bronsted base-catalyzed addition reactions utilizing the [1,2]-phospha-Brook rearrangement to generate carbon-based nucleophiles.
ASIAN JOURNAL OF ORGANIC CHEMISTRY
(2023)
Article
Chemistry, Multidisciplinary
Azusa Kondoh, Kohei Aita, Masahiro Terada
Summary: Efficient methods were developed for the synthesis of furan-fused tricyclic compounds using a regiodivergent intramolecular carbometalation strategy. Two different sequences were employed, resulting in 2,3,4,5-tetrasubstituted naphtho[1,2-b]furans and 2,3-disubstituted 4-alkylidene-4H-indeno[1,2-b]furans. These methods provide access to a wide range of polysubstituted naphtho[1,2-b]furans and indeno[1,2-b]furans in a positional selective manner.
CHEMISTRY-A EUROPEAN JOURNAL
(2023)
Article
Chemistry, Organic
Azusa Kondoh, Sena Takada, Kohei Aita, Masahiro Terada
Summary: A methodology for the formal addition of beta-acylalkenyl anions was developed using the [1,2]-phospha-Brook rearrangement under Bronsted base catalysis. The two-step reaction involves catalytic addition of alpha-oxygenated propargyl anions generated via [1,2]-phospha-Brook rearrangement to electron-deficient ketones and subsequent alcoholysis to obtain tertiary alcohols with an enone moiety. This study provides a rare example of a catalytic carbon-carbon bond formation reaction of beta-acylalkenyl anion equivalents, offering access to synthetic building blocks that are usually difficult to obtain.
EUROPEAN JOURNAL OF ORGANIC CHEMISTRY
(2023)
Article
Chemistry, Organic
Shigenobu Umemiya, Naoya Shinagawa, Masahiro Terada
Summary: A scalable total synthesis of leucascandrolide A macrolactone has been achieved in 17 steps with a longest linear sequence and a yield of 31.2% from readily available feedstocks. The key steps in this synthesis include enantioselective allylation reaction using chiral phosphoric acid (CPA)/CuBr cooperative catalysis and diastereoselective catalytic crotylation in the presence of CPA with CuCl. These catalytic reactions can be performed on a gram scale and result in excellent stereoselectivities.
Article
Chemistry, Organic
Sheng Zhang, Hidenori Matsuyama, Itaru Nakamura, Masahiro Terada, Tienan Jin
Summary: A tandem oxidative ring expansion was developed to construct negatively curved polycyclicarenes with oxepine and thiepine. Mechanistic studies revealed that a unexpected [4+2] cycloadduct of o-biphenyl-linked methylenexanthenes and o-chloranil played a crucial role in the FeCl3-mediated expansion process.
Article
Chemistry, Multidisciplinary
Taishi Nakanishi, Masahiro Terada
Summary: Computational analyses have shown that the stability of the transition state in enantioselective reactions is determined by the distortion of the catalyst and substrates, as well as their interactions. Two strategies, namely, distortion strategy and interaction strategy, can be employed to improve enantiomeric excess. The distortion strategy destabilizes the transition state of the minor pathway, while the interaction strategy focuses on stabilizing the transition state of the major pathway to enhance the reaction rate. In our study, we used the interaction strategy to reinforce hydrogen bonding and successfully improved the enantioselectivity and reaction rate in a chiral phosphoric acid-catalyzed enantioselective Diels-Alder reaction.
Article
Chemistry, Multidisciplinary
Mao Suzuki, Masahiro Terada, Itaru Nakamura
Summary: The [1,3]-nitrogen rearrangement reactions of O-aryl ketoximes were promoted by N-heterocyclic carbene (NHC)-copper catalysts and BF3 center dot OEt2 as an additive, affording ortho-aminophenol derivatives in good yields. The reaction of substrates with electron-withdrawing substituents on the phenol moiety are accelerated by adding silver salt and modifying the substituent at the nitrogen atom. Density functional theory calculations suggest that the rate-determining step of this reaction is the oxidative addition of the N-O bond of the substrate to the copper catalyst. The negative rho values of the substituent at both the oxime carbon and phenoxy group indicate that the donation of electrons by the oxygen and nitrogen atoms accelerates the oxidative addition.
Article
Chemistry, Multidisciplinary
Taishi Nakanishi, Masahiro Terada
Summary: A new exo-selective Diels-Alder reaction, which differs from the conventional endo-selective reaction, has been developed. By using a dual-functional Brønsted acid catalyst and a sterically less demanding acyclic diene, the reaction was successfully achieved. Experimental results demonstrated that the combined use of the dual-functional acid catalyst and the conformationally restricted diene was crucial for the reaction.
Article
Chemistry, Multidisciplinary
Satavisha Kayal, Jun Kikuchi, Naoya Shinagawa, Shigenobu Umemiya, Masahiro Terada
Summary: This study achieved a highly efficient and enantioselective reaction through the use of a co-catalyst system, resulting in enantioenriched compounds and the recovery of the starting material. It provides a new synthetic method for the synthesis of multifunctional compounds.
Article
Chemistry, Organic
Azusa Kondoh, Masahiro Terada
Summary: A new methodology utilizing Bronsted base catalysis was developed to introduce functional groups into organic molecules using a keto or formyl group as the connecting site. The reaction efficiently proceeded with the aid of a phosphazene base catalyst, P2-tBu, giving densely functionalized phosphonates.
ORGANIC & BIOMOLECULAR CHEMISTRY
(2022)
