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A novel method for the concise synthesis of cyclohepta[b]indoles in high yields was developed. The method involves a visible-light-induced, photocatalyzed [2+2]-cycloaddition/ retro-Mannich-type reaction of enaminones. Experimental and computational studies suggested that the reaction is a photoredox process initiated by single-electron oxidation of an enaminone moiety, which undergoes subsequent cyclobutane formation and rapidly fragmentation in a radical-cation state to form cyclohepta[b]indoles.
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http://dx.doi.org/10.1002/anie.202101104 | DOI Listing |
ACS Cent Sci
May 2025
College of Chemistry & Materials Engineering, Wenzhou University, Wenzhou 325035, China.
Significant advancements have been made in the catalytic asymmetric dearomatization of indoles for constructing valuable chiral polycyclic N-heterocycles. However, the asymmetric dearomative cyclopropanation of indoles continues to pose a formidable challenge. Furthermore, the diverse transformations of indoline-fused cyclopropanes via strain release remain largely unexplored, potentially unveiling new chemistry.
View Article and Find Full Text PDFOrg Lett
February 2025
Department of Chemistry, Indian Institute of Technology Guwahati, North Guwahati, Assam 781039, India.
A diastereo- and enantioselective (3 + 3)-cycloannulation of in situ generated carbonyl ylides and ()-3-benzylidene-3-indoles enabled by cooperative Rh/chiral phosphoric acid catalysis is reported. This study is the first to describe an enantioselective synthesis of cyclohepta[]indole with an oxa-bridged motif. The scope of the reaction is broad, and the oxa-bridged cyclohepta[]indole products were obtained in moderate to good yields and with excellent diastereoselectivities and good to high enantioselectivities.
View Article and Find Full Text PDFOrg Lett
June 2024
Christian Doppler Laboratory for Entropy-Oriented Drug Design, Institute of Organic Chemistry, University of Vienna, 1090 Vienna, Austria.
We describe the single-step formation of complex tetracyclic fused scaffolds enabled by (3 + 2) cycloaddition of azomethine ylides. Various indoles, N-protecting groups, and amino acids are well tolerated. The products are obtained in a catalyst-free manner with moderate to excellent yield and high diastereoselectivity.
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May 2024
Advanced Research Centre and Department of Chemistry, University of Science and Technology Meghalaya, Ri-Bhoi, Meghalaya, 793101, India.
Indole, a ubiquitous and structurally versatile aromatic compound, has emerged as a key player in the synthesis of diverse heterocyclic frameworks via cycloaddition reactions. These reactions are completely atom-economical and, hence, are considered as green reactions. This review article provides a comprehensive overview of the pivotal role played by indole in the construction of complex and biologically relevant heterocyclic compounds.
View Article and Find Full Text PDFChemistry
June 2024
School of chemical sciences, Indian Association for the Cultivation of Science, Jadavpur, 700032, Kolkata, India.
Cyclohepta[b]indoles, prevalent in natural products and pharmaceuticals, are conventionally accessed via metal or Lewis acid-mediated cycloadditions with prefunctionalized substrates. Our study introduces an innovative sequential catalytic assembly for synthesizing cyclohepta[b]indoles from readily available isatin derivatives. The process involves three catalytic sequences: ring-closing metathesis, catalytic hydrogenation, and acid-catalyzed ring expansion.
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