A highly efficient Rh(III)-catalyzed oxidative C-H/C-H cross-coupling of [1,2,4]triazolo[1,5- a]pyrimidines (TAP) with indoles and pyrroles has been developed, which provides an opportunity to rapidly assemble a large library of novel excited-state intramolecular proton transfer (ESIPT) fluorophores. The resulting 7-(pyrrol-2-yl)TAPs only show the enol-form emission, while 7-(indol-2-yl)TAPs would undergo an ESIPT process and mainly exhibit the keto-form emission. In highly polar solvents, the enol-form emission of 7-(indol-2-yl)TAPs is enhanced significantly, thus showing the dual emission of enol and keto forms.
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http://dx.doi.org/10.1021/acs.orglett.9b01238 | DOI Listing |
Chemistry
January 2025
Department of chemistry, Indian Institute of Technology Guwahati, Guwahati, 781039, India.
A cobalt(III)-catalyzed dual C(sp)-H/C(sp)-H activation of 2-arylimidazopyridines and its annulation with N-substituted maleimides leads to polycyclic aromatic heterocycles. This sustainable oxidative annulation uses earth-abundant, less toxic, and cost-effective cobalt(III) catalyst that complement expensive 2nd and 3rd-row metals. This oxidative annulation features a broad substrate scope with very good functional group tolerance.
View Article and Find Full Text PDFChem Commun (Camb)
November 2024
Organometallic Synthesis and Catalysis Lab, Organic Chemistry Division, CSIR-National Chemical Laboratory (CSIR-NCL), Dr. Homi Bhabha Road, Pune - 411 008, India.
We report the first regioselective C2-C7 oxidative coupling of indoles using a palladium catalyst upon the strategic installation of -pyridinyl and C3-carbonyl, which delivers 2,7-biindoles with a broad scope (25 examples; up to 93% yield). Isolation of the catalytic intermediate reveals the initial activation of the C(7)-H bond, followed by the C(2)-H bond in indoles, and the reaction proceeds a Pd(II)/Pd(0) pathway.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
January 2025
Hefei National Research Center for Physical Sciences at the Microscale and Department of Chemistry, University of Science and Technology of China, Hefei, 230026, China.
Oxidative cross-dehydrogenative C-H/C-H functionalizations represent an exemplary approach for synthesizing carbonyl compounds via α-heteroarylation. Here we present the development of a direct anodic oxidative coupling process between 2-acylimidazoles and divergent heterocyclic systems including indole, pyrrole, and furan, facilitated by ferrocene-assisted asymmetric nickel electrocatalysis with high levels of enantioselectivity. Mechanistic investigations indicate that the reaction initially involves the formation of a chiral Ni-bound α-carbonyl radical, which is then captured by the heteroarene radical cation via intermolecular stereoselective radical/radical cation coupling.
View Article and Find Full Text PDFChem Asian J
December 2024
Key Laboratory of Medicinal Chemistry for Natural Resource (Yunnan University), Ministry Education, School of Pharmacy, School of Chemical Science and Technology, Yunnan University, Kunming, 650091, P. R. China.
2,3'-Bisindoles with C-C linkages have attracted interest in medicinal chemistry, yet their synthesis is intricate with many steps. Notably, direct C-H/C-H cross-coupling of non-directed heteroaromatics remains challenging, often requiring precious metals and oxidants to enhance coupling efficiency. Herein, we present a copper-catalyzed C-H/C-H cross-coupling method for N-substituted indoles without directing groups, facilitated by molecular oxygen under gentle conditions.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
September 2024
Engineering Research Center of Photoenergy Utilization for Pollution Control and Carbon Reduction, State Key Laboratory of Green Pesticide, College of Chemistry, Central China Normal University, Wuhan, 430079, China.
Herein, we describe an innovative approach to the asymmetric electrochemical α-alkylation of aldehydes facilitated by a newly designed bifunctional chiral electrocatalyst. The highly efficient bifunctional chiral electrocatalyst combines a chiral aminocatalyst with a redox mediator. It plays a dual role as a redox mediator for electrooxidation, while simultaneously providing remarkable asymmetric induction for the stereoselective α-alkylation of aldehydes.
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