4-Vinylphenyl-substituted squaramides have been tested as organocatalysts for the diastereo- and enantioselective synthesis of trisubstituted benzopyrans via an oxa-Michael intramolecular nitro-Michael cascade reaction. Both the enantio- and diastereoselection were good to moderate, depending on the nature of the chiral scaffold in the catalyst. The diastereoselection is better for the most active catalyst because the final products epimerize at C-3 along the time. Supported squaramide sq- prepared by copolymerization of sq- with styrene and divinylbenzene is also effective in promoting the cascade reaction, and it is recoverable and reusable for five cycles maintaining the activity.
Download full-text PDF |
Source |
|---|---|
| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6644291 | PMC |
| http://dx.doi.org/10.1021/acsomega.8b02302 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Asymmetric desymmetrization of 2,5-cyclohexadienones initiated by organocatalytic conjugate addition to 4-nitro-5-styrylisoxazoles.
Chem Commun (Camb)
December 2024
Department of Chemistry, Indian Institute of Technology Jammu, Jagti, NH-44, Nagrota Bypass, Jammu 181221, J&K, India.
A highly regio-, enantio- and diastereo-selective strategy involving initial enantioselective conjugate addition to 4-nitro-5-styrylisoxazoles serves as a key step for the desymmetrization of 2,5-cyclohexadienones has been disclosed. We have designed a new class of 2,5-cyclohexadienones appended with 4-nitro-5-styrylisoxazoles to undergo organocatalytic asymmetric double or triple conjugate addition in a domino sequence depending on the substrate type leading to desymmetrization of the 2,5-cyclohexadienone core. The developed protocol allows the construction of a valuable hydrophenanthrene core or a unique bridged scaffold bearing multiple chiral centers with excellent enantio- (up to >99.
View Article and Find Full Text PDFPhotoredox/Cobalt-Catalyzed Chemo-, Regio-, Diastereo- and Enantioselective Reductive Coupling of 1,1-Disubstituted Allenes and Cyclobutenes.
Angew Chem Int Ed Engl
December 2024
Shanghai Institute of Organic Chemistry, State Key Lab of Organometallic Chemistry, 345 Lingling Road, 200032, Shanghai, CHINA.
A dual photoredox/cobalt-catalyzed protocol for chemo-, regio-, diastereo- and enantioselective reductive coupling of 1,1-disubstituted allenes and cyclobutenes through chemo-, regio-, diastereo- and enantioselective oxidative cyclization followed by stereoselective protonation promoted by a chiral phosphine-cobalt complex is presented. Such process represents an unprecedented reaction pathway for cobalt catalysis that enables selective transformation of the less sterically congested alkenes of 1,1-disubstituted allenes with cyclobutenes, incorporating a broad scope of tetrasubstituted alkenes into the cyclobutane scaffolds in up to 86% yield, >98:2 chemo- and regioselectivity, >98:2 dr and >99.5:0.
View Article and Find Full Text PDFAsymmetric synthesis of spiro[oxindole-3,2'-pyrrolidine]s through organocatalytic 1,3-dipolar cycloaddition cycloreversion of precursor isatinimine homodimers.
Org Biomol Chem
December 2024
Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan.
The chiral amine catalyzed diastereo- and enantioselective [3 + 2] cycloaddition between isatin-derived azomethine ylides and α,β-unsaturated aldehydes was successfully carried out to afford spiro[oxindole-3,2'-pyrrolidine]s. It was anticipated that the formation of azomethine ylides occurred the cycloreversion of dispirooxindole-imidazolidines, which are precursor imine homodimers, in aqueous solvents.
View Article and Find Full Text PDFPd/Cu Catalyzed Asymmetric Allylation for Stereodivergent Synthesis of Glutamic Acid Derivatives.
Chemistry
December 2024
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai, 200032, China.
A synergistic Pd/Cu catalyst system has been developed for stereodivergent transformation of Morita-Baylis-Hillman (MBH) carbonates and Schiff bases derived from simple amino acids to afford a series of optically active β-branched γ-methyleneglutamic acid derivatives with adjacent tertiary/tertiary and quaternary/tertiary stereocenters in high yields (up to 96 %) with excellent diastereo- and enantioselectivities (>20/1 dr and >99 % ee in most cases) under mild conditions. The use of SKP ligand is disclosed to be crucial for the success of the transformation, and in particular allowing the reaction to proceed at low catalyst loading (0.02 mol % for Pd and 0.
View Article and Find Full Text PDFApplication of β-Keto Acylpyrazoles as 2C Synthons in Asymmetric Cyclizations of -Hydroxychalcones: Stereoselective Construction of -3,4-Dihydrocoumarins.
J Org Chem
December 2024
Institute and State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin 300071, P. R. China.
An asymmetric tandem esterification/Michael addition reaction of β-keto acylpyrazoles with -hydroxychalcones has been established under the catalysis of a bifunctional squaramide-tertiary amine. A wide variety of biorelevant 3,4-dihydrocoumarin derivatives were generally obtained in high yields (up to 93%) with excellent diastereo- and enantioselectivities (>19:1 dr, up to 93% ee) under mild reaction conditions. This reaction represents the successful application of β-keto acylpyrazoles as 2C building blocks in catalytic asymmetric cyclizations.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!