951899-40-4Relevant academic research and scientific papers
Scope, Limitations and Mechanistic Analysis of the HyperBTM-Catalyzed Acylative Kinetic Resolution of Tertiary Heterocyclic Alcohols**
Smith, Samuel M.,Greenhalgh, Mark D.,Feoktistova, Taisiia,Walden, Daniel M.,Taylor, James E.,Cordes, David B.,Slawin, Alexandra M. Z.,Cheong, Paul Ha-Yeon,Smith, Andrew D.
supporting information, (2021/11/16)
The full scope and limitations of the catalytic acylative kinetic resolution of a range of tertiary heterocyclic alcohols (78 examples, s up to >200) is reported under operationally-simple conditions, using low loadings of a commercially available Lewis basic isothiourea catalyst, HyperBTM (generally 1 mol %). The protocol is highly effective for the kinetic resolution of 3-substituted 3-hydroxyoxindole and α-substituted α-hydroxylactam derivatives bearing up to three potential recognition motifs at the stereogenic tertiary carbinol center. The full power of this methodology has been showcased through the synthesis of highly enantioenriched biologically-active target compounds in both enantiomeric forms. To provide further insight into the reaction mechanism, a detailed kinetic analysis of this Lewis base-catalyzed acylation of tertiary alcohols is reported using the variable time normalization analysis (VTNA) method.
Diastereo- and Enantioselective Synthesis of Borylated 3-Hydroxyoxindoles by Addition of gem-Diborylalkanes to Isatins
Chen, Fen-Er,Li, Hong-Yan,Xiao, You-Cai,Xiong, Tong,Zhou, Li-Yan,Zhou, Yuan
supporting information, p. 791 - 796 (2022/01/28)
The catalytic asymmetric synthesis of borylated 3-hydroxyoxindoles by addition of gem-diborylalkanes to isatins is disclosed. Chiral 3-hydroxyoxindoles bearing two contiguous stereogenic centers were produced in up to >20:1 dr and 99% ee. The synthetic utility of the corresponding products is presented through several transformations of the boryl moiety. This report provides an efficient strategy to incorporate a boryl functional group toward the synthesis of 3-hydroxyoxindoles.
Catalytic Asymmetric Halogenation/Semipinacol Rearrangement of 3-Hydroxyl-3-vinyl Oxindoles: A Stereodivergent Kinetic Resolution Process
Cao, Weidi,Dai, Li,Feng, Xiaoming,Hu, Xinyue,Liu, Wen,Zeng, Zi,Zhou, Yuqiao
supporting information, p. 26599 - 26603 (2021/11/16)
A highly enantioselective halogenation/semipinacol rearrangement of isatin-derived allylic alcohols has been developed with a chiral N,N′-dioxide/ScIII complex as catalyst. This strategy involved a pivotal stereodivergent kinetic resolution process and provided a facile and efficient entry to optically active halo-substituted quinolone derivatives and quinoline alkaloids with a quaternary stereocenter simultaneously under mild reaction conditions. Based on the control experiments together with kinetic studies and DFT calculations, a possible catalytic cycle was proposed to illustrate the reaction process and enantiocontrol.
Organocatalytic Asymmetric Synthesis of Aza-Spirooxindoles via Michael/Friedel-Crafts Cascade Reaction of 1,3-Nitroenynes and 3-Pyrrolyloxindoles
Ni, Qijian,Wang, Xuyang,Zeng, Da,Wu, Qianling,Song, Xiaoxiao
supporting information, p. 2273 - 2278 (2021/04/05)
An asymmetric [3+3] cyclization of nitroenynes and 3-pyrrolyloxindoles has been realized with a chiral bifunctional squaramide catalyst. This Michael/Friedel-Crafts cascade strategy provides a facile and efficient access to enantioenriched polycyclic aza-spirooxindoles with 32-95% isolated yields and excellent stereocontrol under mild reaction conditions.
Carbene-Catalyzed Enantioselective Aromatic N-Nucleophilic Addition of Heteroarenes to Ketones
Liu, Yonggui,Luo, Guoyong,Yang, Xing,Jiang, Shichun,Xue, Wei,Chi, Yonggui Robin,Jin, Zhichao
supporting information, p. 442 - 448 (2019/11/25)
The aromatic nitrogen atoms of heteroarylaldehydes are activated by carbene catalysts to react with ketone electrophiles. Multi-functionalized cyclic N,O-acetal products are afforded in good to excellent yields and optical purities. Our reaction involves the formation of an unprecedented aza-fulvene-type acylazolium intermediate. A broad range of N-heteroaromatic aldehydes and electron-deficient ketone substrates works effectively in this transformation. Several of the chiral N,O-acetal products afforded through this protocol exhibit excellent antibacterial activities against Ralstonia solanacearum (Rs) and are valuable in the development of novel agrichemicals for plant protection.
Asymmetric Conjugate Addition of Ethylene Sulfonyl Fluorides to 3-Amido-2-oxindoles: Synthesis of Chiral Spirocyclic Oxindole Sultams
Chen, Jie,Huang, Bao-Qin,Wang, Zeng-Qing,Zhang, Xue-Jing,Yan, Ming
supporting information, p. 9742 - 9746 (2019/11/28)
An enantioselective conjugate addition of ethylene sulfonyl fluorides to 3-amido-2-oxindoles has been developed. Quinine-derived squaramides were identified as efficient catalysts. A series of spirocyclic oxindole sultams were prepared with excellent yields and enantioselectivities. A reaction mechanism via bifunctional activation was proposed.
A C=O???Isothiouronium Interaction Dictates Enantiodiscrimination in Acylative Kinetic Resolutions of Tertiary Heterocyclic Alcohols
Greenhalgh, Mark D.,Smith, Samuel M.,Walden, Daniel M.,Taylor, James E.,Brice, Zamira,Robinson, Emily R. T.,Fallan, Charlene,Cordes, David B.,Slawin, Alexandra M. Z.,Richardson, H. Camille,Grove, Markas A.,Cheong, Paul Ha-Yeon,Smith, Andrew D.
supporting information, p. 3200 - 3206 (2018/02/22)
A combination of experimental and computational studies have identified a C=O???isothiouronium interaction as key to efficient enantiodiscrimination in the kinetic resolution of tertiary heterocyclic alcohols bearing up to three potential recognition motifs at the stereogenic tertiary carbinol center. This discrimination was exploited in the isothiourea-catalyzed acylative kinetic resolution of tertiary heterocyclic alcohols (38 examples, s factors up to >200). The reaction proceeds at low catalyst loadings (generally 1 mol %) with either isobutyric or acetic anhydride as the acylating agent under mild conditions.
Development of Novel Chloramphenicol Scaffold-Based Chiral Hydroxyl Oxazoline Ligands and Their Application to the Asymmetric Alkynylation of Isatins
Chen, Lei,Huang, Guanxin,Liu, Minjie,Huang, Zedu,Chen, Fen-Er
supporting information, p. 3497 - 3501 (2018/09/14)
The synthesis of new chloramphenicol base-derived chiral hydroxyl oxazoline ligands, and their use in the first Zn(OTf)2-catalyzed enantioselective alkynylation of isatins are described. This transformation features mild reaction conditions, a remarkably broad substrate scope, and excellent functional group tolerance, affording the corresponding tertiary propargylic alcohols in high yields and with high enantioselectivities. The application of chiral hydroxyl oxazolines as ligands in Zn(II)-catalyzed asymmetric alkynylation reactions is unprecedented. (Figure presented.).
Organocatalytic Asymmetric Synthesis of Bridged Acetals with Spirooxindole Skeleton
Balha, Megha,Pan, Subhas Chandra
, p. 14703 - 14712 (2018/11/23)
The first highly diastereo- and enantioselective synthesis of bridged O,O-acetals embedded with spirooxindoles has been developed. Dioxindoles and 2-hydroxy cinnamaldehydes were employed as the reaction partners in this method. The desired products were obtained via diaryl prolinol TBS ether catalyzed Michael reaction followed by acetal formation with TFA.
Stereochemical surprises in the lewis acid-mediated allylation of isatins
Vyas, Devendra J.,Froehlich, Roland,Oestreich, Martin
supporting information; experimental part, p. 6720 - 6723 (2010/12/19)
The BF3·OEt2-mediated allylation of isatin with an α-chiral allylic stannane is diastereo- and enantioselective. Conversely, allylation of any substituted isatin employing the identical protocol is not diastereoselective at all and o
