A transition metal-free and oxidation-free dearomatization of phenols through conjugate addition to generated indol-2-one from 3-bromooxindole is detailed in this report. This methodology offers an effective approach for the synthesis of a range of 3-substituted oxindoles containing contiguous quaternary carbon centers (CQCCs) with yields of up to 99%. The reaction is characterized by mild conditions, exceptional efficiency, environmental compatibility, favorable functional group tolerance, and scalability to large-scale production.
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http://dx.doi.org/10.1039/d4ob01163e | DOI Listing |
J Org Chem
December 2024
College of Biotechnology and Pharmaceutical Engineering, State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, 30 Puzhu Rd S., Nanjing 211816, China.
An electrochemical reductive bimolecular cycloaddition of 2-arylideneindane-1,3-diones has been reported for the synthesis of spirocyclopentanole indane-1,3-diones bearing five contiguous stereocenters with vicinal tetrasubstituted stereocenters, especially involving a quaternary carbon center, in moderate to good yields and excellent diastereoselectivities. The present protocol features mild reaction conditions, no external chemical redox reagents, excellent atom economy, and gram-scale synthesis. In addition, a mechanistic investigation indicates that the reactions proceed through a radical pathway.
View Article and Find Full Text PDFJ Org Chem
December 2024
College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou, Gansu 730070, China.
In this study, the readily available and inexpensive Sc(OTf) was utilized to activate ortho-benzoyl diazo compounds to in situ generate highly reactive cyclic 1,3-dipoles, which underwent a regioselective [4 + 3] cycloaddition with dioxopyrrolidines, yielding the [4.2.1]-oxabridged scaffolds bearing multiple contiguous quaternary carbon centers with high diastereoselectivities.
View Article and Find Full Text PDFChem Asian J
December 2024
IISER Bhopal: Indian Institute of Science Education and Research Bhopal, Chemistry, 462066, Bhopal, INDIA.
Natural product synthesis has been the prime focus for the development of new chemical transformations and the drug discovery. The dimeric and oligomeric hexahydropyrrolo[2,3-b]indole alkaloids represent a architecturally intriguing class of cyclotryptamine alkaloids. These alkaloids share contiguous stereogenic centers with vicinal all-carbon quaternary stereogenic centers.
View Article and Find Full Text PDFChem Sci
December 2024
Department of Chemistry and Chemical Biology, Stevens Institute of Technology Hoboken NJ 07307 USA
Allylic diboronates are highly valuable reagents in organic synthesis. Existing methods predominantly yield alkyl-substituted allylic diboronates, while the incorporation of electrophilic carbonyl groups conjugated to these allylic systems remains unknown. We present a strain-release promoted cycloaddition-based strategy that enabled access to unprecedented carbonyl conjugated secondary allylic diborons.
View Article and Find Full Text PDFChemistry
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.
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