Ytterbium-Catalyzed Intramolecular [3 + 2] Cycloaddition based on Furan Dearomatization to Construct Fused Triazoles
The 1,2,3-triazole-containing polycyclic architecture widely exists in a broad spectrum of synthetic bioactive molecules, and the development of expeditious methods to synthesize these skeletons remains a challenging task. In this work, the catalytic cyclization of biomass-derived 2-furylcarbinols with an azide to form fused triazoles is described. This approach takes advantage of a single catalyst Yb(OTf)3 and operates via a furfuryl-cation-induced intramolecular [3 + 2] cycloaddition/furan ring-opening cascade.
Two Types of Cross-Coupling Reactions between Electron-Rich and Electron-Deficient Alkenes Assisted by Nucleophilic Addition Using an Organic Photoredox Catalyst
Two types of photoreactions between electronically differentiated donor and acceptor alkenes assisted by nucleophilic addition using an organic photoredox catalyst efficiently afforded 1:1 or 2:1 cross-coupling adducts. A variety of alkenes and alcohols were employed in the photoreaction. Control of the reaction pathway (i.e., the formation of the 1:1 or 2:1 adduct) was achieved by varying the concentration of the alcohol used. Detailed mechanistic studies suggested that the organic photoredox catalyst acts as an effective electron mediator to promote the formation of the cross-coupling adducts.
Enantioselective synthesis of cis-α-substituted cycloalkanols and trans-cycloalkyl amines thereof
The diastereo- and enantioselective syntheses of trans-cycloalkyl amines was accomplished through a three-step sequence consisting of: (1) asymmetric transfer hydrogenation through dynamic kinetic resolution of bicyclic and monocyclic α-substituted ketones using HCO2H/Et3N as the hydrogen source and TsDPEN-based Ru(II) catalysts, (2) nucleophilic hydroxyl to azide substitution of the resulting cis-cycloalkanols using diphenyl phosphoryl azide under modified Mitsunobu conditions, and (3) reduction of the trans-azide intermediates with LiAlH4 of PPh3/H2O to the desired targets.
Fernández, Rosario,Ros, Abel,Magriz, Antonio,Dietrich, Hansj?rg,Lassaletta, José M.
p. 6755 - 6763
(2008/02/11)
Synthesis of Ketones by Cyclization of Cyano and Acetylenic Radicals: Use of δ-Hydroxy Nitriles and δ- or ε-Hydroxy Acetylenes
The radical intermediates generated by deoxygenation of alcohols undergo intramolecular ring closure when suitably located triple bonds (CC or CN) are present; the reaction provides a new synthesis of bicyclic ketones from either monocyclic ketones or cyclic olefins.
Clive, Derrick L. J.,Beaulieu, Pierre L.,Set, Lu
p. 1313 - 1314
(2007/10/02)
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