Oxabicyclic alkenes can react with electron-deficient terminal alkynes in the presence of a gold catalyst under mild conditions, affording the corresponding addition products in moderate yields. When using alkynyl esters as substrates, the (Z)-acrylate derivatives are obtained. Using but-3-yn-2-one (ethynyl ketone) as a substrate, the corresponding addition product is obtained with (E)-configuration. The proposed mechanism of these reactions is also discussed.
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http://dx.doi.org/10.3762/bjoc.9.233 | DOI Listing |
J Org Chem
November 2024
Department of Chemistry, University of Toronto, 80 St. George St., Toronto, ON M5S 3H6, Canada.
We report enantioselective ring-openings of oxabicyclic alkenes with azole nucleophiles, generating heterocycle-bearing dihydronaphthalene products. Pyrazoles, triazoles, tetrazoles, and benzo-fused derivatives participate in the ring-opening, with the level of regioselectivity depending on the type and substitution pattern of the heterocyclic partner. Electron-withdrawing azole substituents have a beneficial effect, suppressing the unproductive complexation of a nitrogen with the Rh(I)-bis(phosphine) catalyst.
View Article and Find Full Text PDFChem Sci
May 2023
Davenport Laboratories, Department of Chemistry, University of Toronto 80 St. George St. Toronto Ontario M5S 3H6 Canada
A palladium-catalyzed spirocyclization reaction is reported, which is proposed to arise insertion of an oxabicycle into a palladacycle, formed from carbocyclization and a C-H functionalization sequence. Mechanistic studies suggest the insertion is diastereoselective and a post-catalytic retro-Diels-Alder step furnishes an alkene, wherein the oxibicycle has served as an acetylene surrogate. Aryl iodides and carbamoyl chlorides were compatible as starting materials under the same reaction conditions, enabling the convergent and complementary synthesis of spirooxindoles, as well as other azacycles.
View Article and Find Full Text PDFJ Am Chem Soc
February 2023
Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemistry, University of Science and Technology of China, Hefei 230026, China.
Spirooxindoles have emerged as promising architectures for engineering biologically active compounds. The diastereodivergent construction of unique scaffolds of this type with full control of continuous chiral centers including an all-carbon quaternary stereogenic center is yet to be developed. Here, we report an unprecedented diastereodivergent desymmetric [3 + 3] annulation of oxabicyclic alkenes with enals enabled by N-heterocyclic carbene (NHC)/Rh cooperative catalysis, leading to a series of enantiomerically enriched spirooxindole lactones with excellent enantioselectivities (up to >99% ee) and diastereoselectivities (up to >95:5 dr).
View Article and Find Full Text PDFChem Commun (Camb)
January 2023
Medicinal and Process Chemistry Division, CSIR-Central Drug Research Institute, Lucknow, 226031, India.
Herein, we disclose the first report on the generation of cyanonitrone from diazoacetonitrile and nitrosoarene, and its subsequent [3+2] cycloaddition with oxabicyclic alkenes to access fused tricyclic cyanoisoxazolidines. Further, this methodology could be extended to access fused tricyclic trifluoromethylated and phosphonylated isoxazolidines. Surprisingly, the reductive ring-opening of cyanoisoxazolidines was followed by a spontaneous lactonization to produce fused tricyclic amino lactones.
View Article and Find Full Text PDFOrg Lett
October 2021
Institute of Catalysis for Energy and Environment, College of Chemistry and Chemical Engineering, Shenyang Normal University, Shenyang 110034, People's Republic of China.
A visible-light-accelerated Rh(III)-catalyzed C-H annulation of aromatic amines with bicyclic alkenes for the synthesis of benzocarbazole derivatives was developed. In this approach, with the cooperation of rhodium catalysis and visible-light irradiation, various aromatic amines reacted with oxabicyclic alkenes and azabicyclic alkenes smoothly at room temperature, delivering the corresponding bridged oxa or aza tetrahydro benzocarbazoles in good to excellent yields. Moreover, a series of benzo[]carbazoles were synthesized conveniently through further aromatization in one pot.
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