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Herein, an unprecedented and modular strategy for the stereoselective construction of functionalized indene scaffolds has been developed a base-promoted, regioselective cascade iodoalkylation of alkynes. Michael addition of methanol to the carbon-carbon double bond initiated the consecutive formation of C-O, C-C, and C-I bonds in a single operation. The product features an exocyclic double bond and versatile functional groups (-CN, -COOEt, -I, -OMe), offering scope for transformation into biologically active pharmacophores. Notably, postfunctionalization of the resulting indene decarboxylative protodeiodination in the presence of N-centered nucleophiles demonstrates the broad synthetic applicability of this protocol, enabling the metal-free construction of challenging C-N bonds and access to amine- and indole-substituted benzofulvenes.
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http://dx.doi.org/10.1021/acs.joc.5c01020 | DOI Listing |
J Org Chem
September 2025
School of Chemistry and Chemical Engineering, Huaibei Normal University, Huaibei, Anhui 235000, P. R. China.
Radical cascade cyclization of alkenes involving the insertion of sulfur dioxide has proven to be a promising tool to access sulfonylnated heterocycle compounds, whereas cyclization of unactivated alkenes has been much less explored. Here, we developed a three-component cascade of unactive alkenes with sulfur dioxide and aryldiazonium tetrafluoroborates to generate sulfonylated tetrahydropyridines and azepines via the cleavage of alkenyl C-H bonds. Moreover, this protocol exhibited excellent chemical and regioselectivity and compatibility with broad functional groups.
View Article and Find Full Text PDFOrg Lett
September 2025
Key Laboratory of Synthetic and Biological Colloids, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, Wuxi, Jiangsu 214122, China.
We demonstrate a copper-catalyzed regioselective cascade oxidative desaturation and imidation of saturated heterocycles using -fluorobenzenesulfonimide (NFSI) as both an oxidant and an imidating reagent. A broad range of substituted piperidones, lactams, and cyclic ketones with high functional group tolerance could be successfully utilized in this transformation. TEMPO-trap experiments, control experiments, and DFT calculations provided supporting evidence for the possible desaturation process.
View Article and Find Full Text PDFOrg Lett
August 2025
Department of Medicinal Chemistry, School of Pharmacy, Hebei Medical University, 361 East Zhongshan Road, Shijiazhuang 050017, China.
Amidst nature's repertoire of small molecule architectures, indole alkaloid-derived privileged scaffolds continuously support innovation in bioactive compound discovery and propel fragment-based drug design. Herein, we realized a metal-free, site-selective, and chemo- and regioselective cross-nucleophile coupling cascade of pluripotent indole-enamine-aniline intermediates by use of λ-iodane-mediated umpolung chemistry. The protocol is applicable toward the divergent synthesis of valuable benzo[]indolo[3,2-][2,6]naphthyridines and azepino[4,5-]indoles, which are very important privileged scaffolds in communesin-, peroforamidine-, and iboga-type alkaloids.
View Article and Find Full Text PDFOrg Lett
August 2025
School of Chemistry, Engineering Research Center of Energy Storage Materials and Devices, Ministry of Education, Xi'an Key Laboratory of Sustainable Energy Material Chemistry, Xi'an Jiaotong University, Xi'an 710049, China.
A visible-light-driven regioselective intramolecular cyclization and oxidation cascade of γ-alkynyl β-sulfonylester is developed. This metal-free approach efficiently affords synthetically useful cyclopentene and cyclohexene skeletons under mild conditions, with TEMPO acting as a dual electron and oxygen atom donor. Mechanism investigations support a radical cyclization/TEMPO-trapping cascade.
View Article and Find Full Text PDFOrg Lett
August 2025
Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai 980-8578, Japan.
We report here a concise and regioselective synthesis of benzofulvene derivatives via an iodine(III)-mediated cyclization cascade of diynes. For 1,2-dialkynylbenzene substrates, the iodanylative cyclization is accompanied by triflation or fluorination, depending on the iodine(III) reagent, affording stereodefined benzofulvene derivatives. In contrast, the reaction of 1,6-diyne substrates is terminated by intramolecular Friedel-Crafts cyclization to deliver fused benzofulvene frameworks.
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