23197-67-3Relevant academic research and scientific papers
Enantioselective Desymmetrization of 2-Aryl-1,3-propanediols by Direct O-Alkylation with a Rationally Designed Chiral Hemiboronic Acid Catalyst That Mitigates Substrate Conformational Poisoning
Estrada, Carl D.,Ang, Hwee Ting,Vetter, Kim-Marie,Ponich, Ashley A.,Hall, Dennis G.
, (2021/04/07)
Enantioselective desymmetrization by direct monofunctionalization of prochiral diols is a powerful strategy to prepare valuable synthetic intermediates in high optical purity. Boron acids can activate diols toward nucleophilic additions; however, the design of stable chiral catalysts remains a challenge and highlights the need to identify new chemotypes for this purpose. Herein, the discovery and optimization of a bench-stable chiral 9-hydroxy-9,10-boroxarophenanthrene catalyst is described and applied in the highly enantioselective desymmetrization of 2-aryl-1,3-diols using benzylic electrophiles under operationally simple, ambient conditions. Nucleophilic activation and discrimination of the enantiotopic hydroxy groups on the diol substrate occurs via a defined chairlike six-membered anionic complex with the hemiboronic heterocycle. The optimal binaphthyl-based catalyst 1g features a large aryloxytrityl group to effectively shield one of the two prochiral hydroxy groups on the diol complex, whereas a strategically placed "methyl blocker"on the boroxarophenanthrene unit mitigates the deleterious effect of a competing conformation of the complexed diol that compromised the overall efficiency of the desymmetrization process. This methodology affords monoalkylated products in enantiomeric ratios equal or over 95:5 for a wide range of 1,3-propanediols with various 2-aryl/heteroaryl groups.
Radical Addition Enables 1,2-Aryl Migration from a Vinyl-Substituted All-Carbon Quaternary Center
Li, Zexian,Shi, Zhuangzhi,Wang, Minyan
supporting information, p. 186 - 190 (2020/11/02)
An efficient method for photocatalytic perfluoroalkylation of vinyl-substituted all-carbon quaternary centers involving 1,2-aryl migration has been developed. The rearrangement reactions use fac-Ir(ppy)3, visible light and commercially available fluoroalkyl halides and can generate valuable multisubstituted perfluoroalkylated compounds in a single step that would be challenging to prepare by other methods. Mechanistically, the photoinduced alkyl radical addition to an alkene leads to the migration of a vicinal aryl substituent from its adjacent all-carbon quaternary center with the concomitant generation of a C-radical bearing two electron-withdrawing groups that is further reduced by a hydrogen donor to complete the domino sequence.
Aryltrifluoromethylative cyclization of unactivated alkenes by the use of PhICF3Cl under catalyst-free conditions
Guo, Jia,Xu, Cong,Liu, Xiaowei,Wang, Mang
supporting information, p. 2162 - 2168 (2019/02/27)
A concise and catalyst-free aryltrifluoromethylative cyclization of unactivated alkenes has been developed herein. The use of PhICF3Cl as a powerful trifluoromethylating agent allows easy transformations. A set of trifluoroethylated carbocycles and aza-hereocycles were efficiently synthesized in good yield and selectivity. A broad substrate scope, mild reaction conditions, and easy operation would make this method well-suited for applications.
OXIDATIVE COUPLING OF ARYL BORON REAGENTS WITH SP3-CARBON NUCLEOPHILES, AND AMBIENT DECARBOXYLATIVE ARYLATION OF MALONATE HALF-ESTERS VIA OXIDATIVE CATALYSIS
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Paragraph 0142; 0143; 0198, (2018/07/29)
Described herein are methods of oxidative coupling of aryl boron reagents with sp3-carbon nucleophiles, and ambient decarboxylative arylation of malonate half-esters via oxidative catalysis.
Copper(I)-USY as a Ligand-Free and Recyclable Catalyst for Ullmann-Type O-, N-, S-, and C-Arylation Reactions: Scope and Application to Total Synthesis
Garnier, Tony,Danel, Mathieu,Magné, Valentin,Pujol, Anthony,Bénéteau, Valérie,Pale, Patrick,Chassaing, Stefan
, p. 6408 - 6422 (2018/05/31)
The copper(I)-doped zeolite CuI-USY proved to be a versatile, efficient, and recyclable catalyst for various Ullmann-type coupling reactions. Easy to prepare and cheap, this catalytic material enables the arylation and heteroarylation of diverse O-, N-, S-, and C-nucleophiles under ligand-free conditions while exhibiting large functional group compatibility. The facility of this catalyst to promote C-O bond formation was further demonstrated with the total synthesis of 3-methylobovatol, a naturally occurring diaryl ether of biological relevance. From a mechanistic viewpoint, two competitive pathways depending on the nature of the nucleophile and consistent with the obtained results have been proposed.
Palladium-Catalyzed Asymmetric Allylic Alkylation of 4-Substituted Isoxazolidin-5-ones: Straightforward Access to β2,2-Amino Acids
Nascimento de Oliveira, Marllon,Arseniyadis, Stellios,Cossy, Janine
supporting information, p. 4810 - 4814 (2018/03/21)
We report here an unprecedented and highly enantioselective palladium-catalyzed allylic alkylation applied to 4-substituted isoxazolidin-5-ones. Ultimately, the process provides a straightforward access to β2,2-amino acids bearing an all-carbon quaternary stereogenic center in great yields and a high degree of enantioselectivity.
Oxidative Coupling of Aryl Boron Reagents with sp3-Carbon Nucleophiles: the Enolate Chan-Evans-Lam Reaction
Moon, Patrick J.,Halperlin, Heather M.,Lundgren, Rylan J.
supporting information, p. 1894 - 1898 (2016/08/31)
Reported is a versatile new oxidative method for the arylation of activated methylene species. Under mild reaction conditions (RT to 40 C), Cu(OTf)2 mediates the selective coupling of functionalized aryl boron species with a variety of stabilized sp3-nucl
Oxidative coupling of aryl boron reagents with sp3-carbon nucleophiles: The enolate chan–evans–lam reaction
Moon, Patrick J.,Halperin, Heather M.,Lundgren, Rylan J.
supporting information, p. 1894 - 1898 (2016/12/03)
Reported is a versatile new oxidative method for the arylation of activated methylene species. Under mild reaction conditions (RT to 40°C), Cu(OTf)2mediates the selective coupling of functionalized aryl boron species with a variety of stabilized sp3-nucleophiles. Tertiary malonates and amido esters can be employed as substrates to generate quaternary centers. Complementing either traditional cross-coupling or SNAr protocols, the transformation is chemoselective in the presence of halogen electrophiles, including aryl bromides and iodides. Substrates bearing amide, sulfonyl, and phosphonyl groups, which are not amenable to coupling under mild Hurtley-type conditions, are suitable reaction partners.
Controlling the Conformational Energy of a Phenyl Group by Tuning the Strength of a Nonclassical CH···O Hydrogen Bond: The Case of 5-Phenyl-1,3-dioxane
Bailey, William F.,Lambert, Kyle M.,Stempel, Zachary D.,Wiberg, Kenneth B.,Mercado, Brandon Q.
, p. 12116 - 12127 (2016/12/23)
Anancomeric 5-phenyl-1,3-dioxanes provide a unique opportunity to study factors that control conformation. Whereas one might expect an axial phenyl group at C(5) of 1,3-dioxane to adopt a conformation similar to that in axial phenylcyclohexane, a series of studies including X-ray crystallography, NOE measurements, and DFT calculations demonstrate that the phenyl prefers to lie over the dioxane ring in order to position an ortho-hydrogen to participate in a stabilizing, nonclassical CH···O hydrogen bond with a ring oxygen of the dioxane. Acid-catalyzed equilibration of a series of anancomeric 2-tert-butyl-5-aryl-1,3-dioxane isomers demonstrates that remote substituents on the phenyl ring affect the conformational energy of a 5-aryl-1,3-dioxane: electron-withdrawing substituents decrease the conformational energy of the aryl group, while electron-donating substituents increase the conformational energy of the group. This effect is correlated in a very linear way to Hammett substituent parameters. In short, the strength of the CH···O hydrogen bond may be tuned in a predictable way in response to the electron-withdrawing or electron-donating ability of substituents positioned remotely on the aryl ring. This effect may be profound: a 3,5-bis-CF3 phenyl group at C(5) in 1,3-dioxane displays a pronounced preference for the axial orientation. The results are relevant to broader conformational issues involving heterocyclic systems bearing aryl substituents.
Nucleophilic Reactivities of 2-Substituted Malonates
Puente, ángel,He, Shanshan,Corral-Bautista, Francisco,Ofial, Armin R.,Mayr, Herbert
supporting information, p. 1841 - 1848 (2016/05/09)
Kinetics of the reactions of 2-substituted malonate anions and 5-substituted Meldrum's acid anions with benzhydrylium ions and structurally related quinone methides have been monitored in dimethyl sulfoxide solution at 20 °C. The resulting second-order rate constants followed the correlation lg k(20 °C) = sN(E + N), which allowed the nucleophile-specific parameters N and sN to be calculated for these highly stabilized carbanions and to integrate them in our comprehensive nucleophilicity scale. Given that the reactions of the benzhydrylium ions with the anions derived from 5-aryl-substituted Meldrum's acids did not proceed to completion, the corresponding equilibrium constants could be determined. In combination with available data for pyridines and benzoate ions, these equilibrium constants provide a direct comparison of the strengths of C-, N-, and O-centered Lewis bases with respect to C-centered Lewis acids.
