5874-61-3Relevant articles and documents
Organocatalytic asymmetric [4+2] cyclization of 2-benzothiazolimines with azlactones: Access to chiral benzothiazolopyrimidine derivatives
Ni, Qijian,Wang, Xuyang,Xu, Fangfang,Chen, Xiaoyun,Song, Xiaoxiao
supporting information, p. 3155 - 3158 (2020/03/23)
An organocatalytic asymmetric domino Mannich/cyclization reaction between 2-benzothiazolimines with azlactones has been successfully developed. With the bifunctional squaramide catalyst, this formal [4+2] cyclization occurs with good to high yields and excellent stereoselectivities (up to 99% ee, >20?:?1 dr), providing an efficient and mild access to chiral benzothiazolopyrimidines bearing adjacent tertiary and quaternary stereogenic centers.
Asymmetric trifluoromethylthiolation of azlactones under chiral phase transfer catalysis
Alemán, José,Bernardi, Luca,Borello, Fabio,Cano, Rafael,Capaccio, Vito,Díaz-Tendero, Sergio,De Riccardis, Francesco,Della Sala, Giorgio,Rodríguez, Ricardo I.,Sicignano, Marina
supporting information, p. 2914 - 2920 (2020/04/28)
The first enantioselective method for the installation of the SCF3 group at the C-4 position of azlactones is described in the present communication under quinidinium phase transfer catalysis. The higher performance of substrates containing electron-rich 2-aryl groups at the azlactone was rationalized using DFT calculations.
Asymmetric Aza-Diels-Alder Reactions of in Situ Generated β,β-Disubstituted α,β-Unsaturated N-H Ketimines Catalyzed by Chiral Phosphoric Acids
He, Shunlong,Gu, Huanchao,He, Yu-Peng,Yang, Xiaoyu
supporting information, p. 5633 - 5639 (2020/07/14)
A novel asymmetric synthesis of dihydropyridinones with vicinal quaternary stereocenters has been realized by asymmetric aza-Diels-Alder reactions of 3-amido allylic alcohols with oxazolones enabled by chiral phosphoric acid catalysis. A series of aryl/alkyl- and alkyl/alkyl-disubstituted 3-amido allylic tertiary alcohols and 4-substituted oxazolones could be well tolerated in these reactions, producing dihydropyridinones with excellent diastereoselectivities and high enantioselectivities. Mechanistic study and control experiments were performed to shed light on the reaction mechanism, in which a configurationally defined β,β-disubstituted α,β-unsaturated N-H ketimine was proposed as the key intermediate.
Rational Design of 2-Substituted DMAP- N-oxides as Acyl Transfer Catalysts: Dynamic Kinetic Resolution of Azlactones
Deng, Yun,Guo, Hai-Ming,Huang, Bin,Li, Ning,Qu, Gui-Rong,Tian, Yin,Wu, Xiao-Xia,Xie, Ming-Sheng
supporting information, p. 19226 - 19238 (2020/11/13)
A novel concept that conversion of chiral 2-substituted DMAP into its DMAP-N-oxide could significantly enhance the catalytic activity and still be used as an acyl transfer catalyst is presented. A new type of chiral 2-substituted DMAP-N-oxides, derived from l-prolinamides, has been rationally designed, facilely synthesized, and applied in the dynamic kinetic resolution of azlactones. Using simple MeOH as the nucleophile, various l-amino acid derivatives were produced in high yields (up to 98% yield) and enantioselectivities (up to 96% ee). Furthermore, α-deuterium labeled l-phenylalanine derivative was also obtained. Experiments and DFT calculations revealed that in 2-substituted DMAP-N-oxide, the oxygen atom acted as the nucleophilic site and the N-H bond functioned as the H-bond donor. High enantioselectivity of the reaction was governed by steric factors, and the addition of benzoic acid reduced the activation energy by participating in the construction of a H-bond bridge. The theoretical chemical study indicated that only when attack directions of the chiral catalyst were fully considered could the correct calculation results be obtained. This work paves the way for the utilization of the C2 position of the pyridine ring and the development of chiral 2-substituted DMAP-N-oxides as efficient acyl transfer catalysts.
Palladium-catalyzed asymmetric decarboxylative allylation of azlactone enol carbonates: Fast access to enantioenriched α-allyl quaternary amino acids
Serra, Massimo,Bernardi, Eric,Marrubini, Giorgio,De Lorenzi, Ersilia,Colombo, Lino
, p. 732 - 741 (2019/01/09)
We report a fast protocol for the synthesis of enantioenriched quaternary 4-allyl oxazol-5-ones. The key step is a Pd-catalyzed enantioselective Tsuji allylation of azlactone allyl enol carbonates, which can be easily prepared starting from racemic α-amino acids. The use of (R,R)-DACH-phenyl Trost chiral ligand allowed the attainment of the allylated derivatives in very good yields (83–98 %) and with ee up to 85 %. Scaling up the allylation protocol to gram quantities did not affect the yields end ee values. The produced 4-allyl azlactones can be converted into the corresponding quaternary amino acids or submitted to further synthetic elaborations exploiting the allyl moiety as a handle for the attachment of alkyl and aryl groups. After hydrolysis of the azlactone ring, the zwitterionic amino acids can be attained in enantiopure or nearly optically pure form through only one recrystallization step.
Enantioselective synthesis of pyrano[2,3-: C] pyrrole via an organocatalytic [4 + 2] cyclization reaction of dioxopyrrolidines and azlactones
Wang, Yichen,Chen, Yuzhen,Li, Xiaoping,Mao, Yukang,Chen, Weiwen,Zhan, Ruoting,Huang, Huicai
supporting information, p. 3945 - 3950 (2019/04/30)
An enantioselective [4 + 2] cyclization reaction of dioxopyrrolidines and azlactones has been successfully developed through a squaramide catalysis strategy. This protocol provides an efficient and mild access to obtain pyrano[2,3-c]pyrrole scaffolds containing contiguous quaternary and tertiary stereogenic centers in excellent yields (up to 99%) with high levels of diastereo- and enantioselectivities (up to 99% ee). Two possible pathways were proposed to explain the observed stereoselectivity.
Asymmetric construction of dihydrobenzofuran-2,5-dione derivatives via desymmetrization of p-quinols with azlactones
Xie, Lihua,Dong, Shunxi,Zhang, Qian,Feng, Xiaoming,Liu, Xiaohua
supporting information, p. 87 - 90 (2019/01/03)
The desymmetrization of p-quinols through a chiral bisguanidinium hemisalt catalyzed enantioselective Michael addition/lactonization cascade reaction with azlactones was reported. 3-Amino-benzofuran-2,5-diones containing a chiral amino acid residue were achieved with up to 99% ee and >19?:?1 dr. An exploration of the structure of the catalyst bisguanidinium was undertaken, revealing a bifunctional catalytic model.
Metal-Free Insertion Reactions of Diazo Carbonyls to Azlactones
De Mello, Amanda C.,Momo, Patrícia B.,Burtoloso, Antonio C. B.,Amarante, Giovanni W.
, p. 11399 - 11406 (2018/09/12)
Insertion reactions of diazo carbonyls to azlactones in basic conditions have been performed. The developed method allows the preparation of a wide range of oxazole derivatives in yields ranging from 74 to 98%. Different substituents on both azlactone rings and diazo carbonyls do not compromise the methodology, even those containing stereogenic centers. Isotopic labeling experiments revealed the mechanism may proceed through a rare diazo carbonyl activation by an ammonium salt derivative.
Group-Assisted Purification Chemistry for Asymmetric Mannich-type Reaction of Chiral N-Phosphonyl Imines with Azlactones Leading to Syntheses of α-Quaternary α,β-Diamino Acid Derivatives ?
Zhang, Haowei,Yang, Zhen,Zhao, Brian Nlong,Li, Guigen
, p. 644 - 655 (2018/01/27)
An asymmetric Mannich-type reaction between chiral N-phosphonyl imines and azlactones [oxazol-5(4H)-ones] has been established under convenient conditions at room temperature. The reaction was performed without using any bases, additives, or catalysts to achieve up to excellent chemical yields and diastereoselectivity for 32 examples. The α-quaternary syn-α,β-diamino acid products were purified simply by washing the crude mixtures with cosolvents, following the group-assisted purification chemistry/technology, without involving traditional chromatography or recrystallization methods. The auxiliary can be readily removed and recycled for reuse. The absolute configuration was unambiguously assigned by X-ray structural analysis.
STRUCTURE AND SYNTHESIS OF HIGHLY FLUORINATED AMINO ACID DERIVATIVES
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Paragraph 0170; 0171; 0172; 0174, (2018/09/19)
Methods of synthesizing polyfluorinated amino acid derivatives are disclosed, along with polyfluorinated amino acid derivatives produced from said methods, as well as compositions containing same. The synthesis methods utilize an oxazolone and a perfluoroarene to produce the polyfluorinated amino acid derivatives.
