An efficient base-promoted C(sp)-H bond functionalization strategy for the synthesis of multisubstituted chromans from the formal [3+3] cycloaddition of benzo[ c]oxepines and electron-rich phenols has been developed. The corresponding 4 H-chromenes can be easily obtained in excellent yields by simple filtration from chromans. Preliminary mechanistic studies indicate that the C-O bond cleavage is the key step for the C(sp)-H bond functionalization and that this reaction could have occurred through tandem C-O bond cleavage/Michael addition/annulation reactions.
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http://dx.doi.org/10.1021/acs.joc.8b00126 | DOI Listing |
Molecules
September 2023
Laboratory of Industrial and Synthetic Organic Chemistry (LISOC), Department of Chemistry and Chemical Technologies, University of Calabria, Via Pietro Bucci 12/C, 87036 Arcavacata di Rende, Italy.
2-Propargyl-1,3-dicarbonyl compounds have been carbonylated under oxidative conditions and with the catalysis of the PdI/KI catalytic system to selectively afford previously unreported 2-(4-acylfuran-2-yl)acetamides in fair to good yields (54-81%) over 19 examples. The process takes place under relatively mild conditions and occurs via a mechanistic pathway involving C-H activation by oxidative monoamincarbonylation of the terminal triple bond of the substrates with formation of 2-ynamide intermediates, followed by 5---cyclization (via intramolecular conjugate addition of the in situ formed enolate to the 2-ynamide moiety) and aromative isomerization.
View Article and Find Full Text PDFChem Commun (Camb)
December 2021
Department of Chemistry, Fudan University, 2005 Songhu Rd, Shanghai, 200438, China.
Chem Rev
July 2017
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences , Fuzhou, Fujian 350002, China.
J Am Chem Soc
June 2006
Department of Applied Chemistry Graduate School of Engineering, Nagoya University, Chikusa, Nagoya 464-8603, Japan.
Highly substituted iodobenzenes were efficiently and regioselectively synthesized from readily available 1,6-diynes via two-step process consisting of silver-catalyzed Csp-H iodination and subsequent ruthenium-catalyzed [2 + 2 + 2] cycloaddition of resultant iododiynes. Some of the obtained iodobenzenes were subjected to palladium-catalyzed C-C bond-forming reactions such as Mizoroki-Heck reaction, Sonogashira reaction, and Suzuki-Miyaura coupling, giving highly conjugated molecules.
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