Article
Chemistry, Organic
Nirmala Mohanta, Pragnya Paramita Samal, Akanksha M. Pandey, Shankhajit Mondal, Sailaja Krishnamurty, Boopathy Gnanaprakasam
Summary: This study introduces a new synthetic methodology using In-(OTf)(3)-catalyzed α-vinylation of various hydroxy-functionalized quaternary carbon centers with in situ generated isobutylene from tert-butyl acetate. It demonstrates that tert-butyl acetate is a nonflammable feedstock and a readily available source for in situ production of vinyl substituents. Furthermore, Ni-(OTf)(2) shows excellent selectivity for methylallylation over vinylation as a catalyst. The sequential rearrangement of peroxyoxindole followed by nucleophilic attack by isobutylene leads to the formation of methylallyl-functionalized 1,4-benzoxazin-3-one derivatives. The reaction mechanism and selectivity are explained using kinetics and density functional theory studies.
JOURNAL OF ORGANIC CHEMISTRY
(2023)
Article
Chemistry, Organic
Clayton P. Donald, Amy Boylan, Truong N. Nguyen, Po-An Chen, Jeremy A. May
Summary: The (IPr)GaCl3/AgSbF6, AgSbF6, and GaCl3 catalysts were found to efficiently catalyze the substitution of the hydroxyl group of secondary and tertiary propargylic alcohols with organoboronic acids via C-C bond formation, and GaCl3 catalyst effectively synthesized all-carbon quaternary propargylic centers. These catalysts demonstrated the ability to perform substitutions at carbons bearing alkyl substituents, a capability that was lacking in other systems. The study showed that highly hindered carbon stereocenters, including quaternary centers bearing doubly ortho-substituted aryl rings, could be accessed efficiently using this method.
Article
Chemistry, Multidisciplinary
Mayuko Isomura, David A. Petrone, Erick M. Carreira
Summary: A robust catalytic system utilizing chiral Ir-phosphoramidite and La(OTf)(3) enables highly enantioselective alkylation reactions of racemic tertiary alpha-allenyl alcohols with tetrasubstituted silyl ketene acetals. The reaction displays broad functional group tolerance and allows efficient generation of beta-allenyl ester products with excellent enantioselectivity, which can be further upgraded in structural complexity via stereoselective metal-catalyzed functionalization reactions.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2021)
Article
Chemistry, Physical
Dingding Xia, Rongkai Wu, Jinxin Wang, Xinyu Han, Yanchuan Li, Qiannan Li, Xin Luan, Xin Hong, Yu Zhang, Wei-Dong Zhang
Summary: This article introduces a visible-light-mediated energy transfer strategy to synthesize highly congested EWG-free cyclopropanes through obtaining donor/donor carbenes from readily available N-tosylhydrazones. This method allows for rapid installation of cyclopropanes into complex bioactive molecules, fluorescent molecules, and other challenging building blocks. Detailed mechanistic reactions and DFT studies demonstrate the role of the photosensitizer, donor/donor carbenes formation, and the necessity of light and a base in the system.
Article
Chemistry, Multidisciplinary
Aaron Pan, Maja Chojnacka, Robert Crowley, Lucas Gottemann, Brandon E. Haines, Kevin G. M. Kou
Summary: This study presents a new dual acid catalyst system involving environmentally benign and readily accessible protic acid and iron for the site-selective tert-butylation of electron-rich arenes. It also develops a synergistic Bronsted/Lewis acid catalyzed aromatic alkylation, filling a gap in the Friedel-Crafts reaction literature. The use of non-allylic, non-benzylic, and non-propargylic tertiary alcohols is explored, leading to the formation of new quaternary carbon centers.
Article
Chemistry, Organic
Yunpeng Zhang, Daoyi Yang, Dengfu Lu, Yuefa Gong
Summary: A photoredox-enabled alkylative dearomatization of protected anilines is described. By using Ir catalyst and light irradiation, an N-carbamoyl-protected aniline and an alpha-bromo-carbonyl compound can be activated simultaneously, leading to the formation of a dearomatized cyclohexadienone imine as the main product through radical recombination. This method allows the preparation of a series of imines with contiguous quaternary carbon centers, which can be further converted into cyclohexadienones, cyclohexadienols, and cyclohexyl amines.
Article
Chemistry, Organic
Binghao Liu, Xiao-Yong Duan, Jiahan Li, Yatong Wu, Yanting Li, Jing Qi
Summary: A new enantio- and diastereoselective reaction has been developed for the synthesis of various spirocyclic bisoxindole alkaloids. This reaction exhibits a broad substrate scope and excellent enantioselectivity, and allows for the creation of two contiguous sterically congested all-carbon quaternary stereocenters.
Review
Chemistry, Multidisciplinary
Weichao Xue, Xiao Jia, Xuan Wang, Xianghua Tao, Zhigang Yin, Hegui Gong
Summary: The transformation of sterically hindered tertiary alkyl electrophiles under nickel-catalyzed conditions to forge C(sp(3))-C bonds and create all-carbon quaternary centers has received increasing attention in recent years. This process involves the activation of tertiary alkyl electrophiles through ionic or radical pathways, benefiting the formation of C-C bonds in coupling reactions and accelerating radical addition reactions.
CHEMICAL SOCIETY REVIEWS
(2021)
Article
Chemistry, Organic
Binghao Liu, Jing Qi, Yatong Wu, Jia-Hui Li, Yanting Li, Xiao-Yong Duan
Summary: In this work, an efficient strategy for the construction of dimeric spirocyclic bisindoline alkaloid derivatives was introduced using NHC-catalyzed enantioselective [3 + 2] annulation of enals with isoindigo. The reaction successfully constructs three contiguous stereogenic centers, including two congested all-carbon quaternary stereogenic centers, in a simple one-step operation.
ORGANIC CHEMISTRY FRONTIERS
(2022)
Article
Chemistry, Organic
Jianming Zhang, Zheng Liang, Simiao Zhang, Lei Chen, Xiaoxue Wang, Yuchan Wang, Jie Feng, Tao Lu, Ding Du, Jian Gao
Summary: An N-heterocyclic carbene-catalyzed asymmetric [3 + 2] annulation of enals with propargylic ketimines has been developed for the facile and enantioselective construction of gamma, gamma-disubstituted pyrrolidin-2-ones. This method features mild reaction conditions, wide functional group tolerance, easy scalability, and high level of enantioselectivity, enriching the chemistry of NHC-bound homoenolates involved in the synthesis of gamma-lactams bearing gamma-quaternary stereogenic centers from acyclic ketimines.
ORGANIC CHEMISTRY FRONTIERS
(2022)
Article
Chemistry, Physical
Xiaodong Tang, Chuan Xiang Alvin Tan, Wai-Lun Chan, Fuhao Zhang, Wenrui Zheng, Yixin Lu
Summary: In this study, we introduced a new type of allenic ketone as a dielectrophilic C4 synthon in phosphine-mediated reactions, enabling a highly enantioselective [4 + 2] annulation. This strategy allowed for the facile creation of spirocyclic bisindoline structures containing two contiguous quaternary stereogenic centers. Synthetic manipulations of the [4 + 2] annulation product led to concise total synthesis of (-)-folicanthine.
Article
Chemistry, Multidisciplinary
Hao-Yuan Liu, Zhen-Yu Zhang, Yi-Ke Zhou, Jia-Hua Chen, Zhen Yang, Yuan-He Li
Summary: This paper presents an efficient strategy for synthesizing the DEFGH rings of phainanoid F, involving a photo-induced electrocyclization and a homoallylic elimination. It is noteworthy that the electrocyclization reaction was used to simultaneously construct two vicinal quaternary carbons in total synthesis, which is a rare example. The strategy outlined here serves as the basis for the total synthesis of Phainanoid F and could be applied in synthesizing other natural products with similar 13,30-cyclodammarane skeletons.
CHEMISTRY-AN ASIAN JOURNAL
(2023)
Article
Chemistry, Organic
Xu Ban, Changxing Chen, Kha Tuan Khoa, Chao Wang, Zhiyong Jiang, Choon-Hong Tan
Summary: A bisguanidinium-catalyzed enantioconvergent SN2X reaction is described for the formation of C(sp3)-O bonds from racemic tertiary bromides and hydroxylamides/phenols, enabling efficient synthesis of bioactive compounds such as enantiopure bicalutamide and chiral fibrates.
ORGANIC CHEMISTRY FRONTIERS
(2023)
Article
Chemistry, Multidisciplinary
Xu Chen, Kaushalendra Patel, Ilan Marek
Summary: An efficient method has been developed for the stereoselective construction of tertiary C-O bonds via stereoinvertive nucleophilic substitution. This method utilizes water, alcohols, and phenols as nucleophiles and demonstrates high tolerance to functional groups, providing a new approach to the formation of highly congested tertiary homoallyl alcohols and ethers.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Multidisciplinary
Tianhong Wang, Youbin Peng, Guanlin Li, Yicong Luo, Yong Ye, Xiaohong Huo, Wanbin Zhang
Summary: The highly regio-, enantio-, and diastereoselective allylic alkylation of 3-alkyl oxindoles through synergistic iridium and copper catalysis provides a series of 3,3-disubstituted oxindole derivatives containing adjacent quaternary and tertiary stereogenic centers in excellent yields, enantiomeric excess, and diastereomeric ratio. The method demonstrates exclusive branched selectivity, excellent enantio- and diastereoselectivities, and good functional compatibility, with the chiral copper catalyst being crucial for achieving high reactivities and diastereoselectivities under mild reaction conditions.
CHEMISTRY-A EUROPEAN JOURNAL
(2021)
