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Direct introduction of silyl radicals to forge C-Si bonds is of central importance in organic synthesis, owing to the formidable potential of silyl groups as coupling partners for further derivatization reactions to achieve more valuable compounds. Cleavage of heteroaromatic endocyclic carbon-heteroatom bonds to assemble C-Si bonds is scarce. Here, we demonstrate a dearomatization silylation of benzofurans and furopyridines via silyl radical addition and C(2)-O bond scission under metal-catalyst-free and mild conditions. Preliminary mechanistic experiments suggest that these transformations involve radical/single-electron transfer and [1,5]-Brook rearrangement processes. This protocol for the total synthesis of Doxepin and oxyresveratrol derivatives is carried out. The silylated products in several transformation reactions have proven to be useful as synthetic intermediates.
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http://dx.doi.org/10.1021/acs.joc.3c01162 | DOI Listing |
J Am Chem Soc
June 2025
The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, California Institute of Technology, MC-101-20, Pasadena, California 91125, United States.
We disclose the first total syntheses of the complex alkaloids Lycojapomine A and B. Our synthetic strategy is built on a dearomatization and stepwise functionalization of a pyrrole starting material, constructing the three-dimensional structure of the target around it. This is enabled by a high-yielding photoinduced primary radical addition from the -hydroxy phthalimide ester and a subsequent silver-catalyzed 5-endo-dig and Aza-silyl-Prins annulation cascade.
View Article and Find Full Text PDFJ Org Chem
February 2025
Advanced Research Institute and School of Pharmaceutical Science, Taizhou University, Jiaojiang, Zhejiang 318000, P. R. China.
A hexafluoroisopropanol (HFIP)-promoted hydrodifluoroalkylation of furans and vinyl ethers with difluorinated silyl enol ethers has been developed. Because of the inherent electron richer nature of furans and the poor nucleophilicity of difluorinated silyl enol ethers, the employment of simple furans as the substrates for nucleophilic dearomatization without a metal or stoichiometric chemical oxidizing reagent is challenging, especially considering the rearomatization driving force and ring fragmentation of the furan ring system. This protocol exploits the formation of oxocarbenium intermediate from furans using HFIP as a proton source to allow the nucleophilic addition of difluorinated silyl enol ethers, which provides an efficient synthetic strategy to install a -difluorinated group into heterocycles.
View Article and Find Full Text PDFOrg Lett
October 2024
Department of Applied Chemistry, Anhui Province Engineering Laboratory for Green Pesticide Development and Application, and Anhui Province Key Laboratory of Crop Integrated Pest Management, Anhui Agricultural University, 230036 Hefei, China.
An intramolecular organocatalytic cascade dearomatizing spirocycloaddition reaction of indole-ynone compounds containing -silyl-naphthol substituents has been developed with the use of a chiral bifunctional thiourea. This process was able to provide various structurally diverse polycyclic spiroindolines in high yields (up to 98%) with excellent stereoselectivities (>20:1 dr, up to 98% ee) involving the formation of carbonylvinylidene -quinone methide intermediates.
View Article and Find Full Text PDFChem Commun (Camb)
October 2024
School of Chemistry and Material Science, Jiangsu Normal University, Xuzhou 221116, China.
The cleavage of heteroaromatic endocyclic carbon-heteroatom bonds to assemble C-Si bonds is scarce. Here, we demonstrate an unprecedented dearomatization silylation of -arylindoles arising from reductive activation initiated by electron-rich silylboronic complexes to deliver silyl styrenes with perfect stereoselectivity.
View Article and Find Full Text PDFFront Chem
June 2024
Department of Chemistry, Inha University, Incheon, Republic of Korea.
Catalytic hydroboration and hydrosilylation have emerged as promising strategies for the reduction of unsaturated hydrocarbons and carbonyl compounds, as well as for the dearomatization of -heteroarenes. Various catalysts have been employed in these processes to achieve the formation of reduced products via distinct reaction pathways and intermediates. Among these intermediates, -silyl enamines and -boryl enamines, which are derived from hydrosilylation and hydroboration, are commonly underestimated in this reduction process.
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