This manuscript discloses an efficient construction of the spirocyclic oxindole-dihydropyranone scaffold via the N-heterocyclic carbene (NHC)-catalyzed oxidative γ-functionalization of α,β-unsaturated aldehydes bearing γ-H with isatin derivatives. The ready availability of the starting materials, easy work-up, mild reaction conditions and the potential utilization value of the products make this strategy attractive.
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http://dx.doi.org/10.1039/c3ob42008f | DOI Listing |
Org Lett
January 2025
Department of Chemistry, Indian Institute of Technology Ropar, Rupnagar, Punjab 140001, India.
Developing asymmetric transformations using electroredox and N-heterocyclic carbene (NHC)-catalyzed radical pathways is still desirable and challenging. Herein, we report an iodide-promoted β-carbon activation (LUMO-lowering process) of enals via electroredox carbene catalysis coupled with a hydrogen evolution reaction (HER). This strategy offers an environmentally friendly and sustainable route for rapidly assembling synthetically useful chiral naphthopyran-3-one in good to excellent yield and enantioselectivity using traceless electrons as inexpensive and greener oxidants.
View Article and Find Full Text PDFJ Phys Chem A
December 2024
School of Chemical Engineering, University of Science and Technology Liaoning, Qianshan Road 185, Anshan 114051, Liaoning, China.
Chemistry
January 2025
Department of Chemistry, Indian Institute of Technology Guwahati, 781039, Guwahati, Assam, India.
Oxidative cleavage of olefins is a useful reaction in organic synthesis. The most well-known catalytic system is the osmium based Lemieux-Johnson catalyst, which generally requires high catalyst loading and tends to suffer from rapid overoxidation to produce the acid predominantly. Hence, the development of a mild, general, and selective method toward the oxidative cleavage of alkenes to carbonyl compounds is highly desired.
View Article and Find Full Text PDFPhys Chem Chem Phys
November 2024
School of Chemical Engineering, University of Science and Technology Liaoning, Anshan, Liaoning 114051, P. R. China.
The mechanism, chemoselectivity and stereoselectivity in the NHC-catalyzed reaction between enals and pyrroles for the synthesis of 5,6-dihydroindolizine were studied using DFT calculations. The cycle for catalytic generation of 5,6-dihydroindolizine proceeds seven steps: (1) addition of the NHC to enal, (2) formation of a Breslow intermediate through [1,2]-proton transfer, (3) oxidation, (4) Michael addition, (5) [2+2] cycloaddition, (6) liberation of NHCs and (7) decarboxylation. Our results show that the presence of DMAP·H lowers the barrier for [1,2]-proton transfer.
View Article and Find Full Text PDFJ Org Chem
November 2024
Department of Chemical Sciences, Indian Institute of Science Education and Research Berhampur, Berhampur, Odisha 760010, India.
We disclose the synthesis of a tricyclic fused N-heterocycle via the NHC-catalyzed annulation of either a ynal or an alkynyl ester with readily accessible benzoxazolyl acetate. While the annulation with ynals requires an oxidant, the reaction with alkynyl esters proceeds via the direct generation of alkynyl acylazolium intermediates with an NHC. With the dearth of catalytic processes to access these 1-benzoxazolo[3,2-]pyridin-1-ones from simple starting materials, this method is especially important.
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