Showing papers by "Zhengkun Yu published in 2017"
TL;DR: Tetrasubstituted furans were efficiently synthesized from Fe(OAc)2-catalyzed C-H/C-H cross-dehydrogenative-coupling reactions of activated carbonyl methylenes with S,S-functionalized internal olefins under oxidative conditions.
54 citations
TL;DR: It is suggested that formal carbene migratory insertion into the olefinic C═C bond is involved in the overall catalytic cycle, demonstrating a new type of carbene insertion reaction for five-membered heterocycle construction.
41 citations
TL;DR: The present protocol provides a convenient route to tetrasubstituted olefins through the C-H alkylation of S, S-functionalized internal ole-fins using simple ethers and toluene derivatives as the coupling partners, ditert-butyl peroxide (DTBP) as the oxidant, and DABCO center dot 6H(2)O as the additive.
Abstract: Mediated by a catalytic amount of FeCl3, the C-H alkylation of S, S-functionalized internal ole-fins, i.e., alpha-oxo ketene dithioacetals and their analogues, was efficiently achieved using simple ethers and toluene derivatives as the coupling partners, ditert-butyl peroxide (DTBP) as the oxidant, and DABCO center dot 6H(2)O as the additive. The alkylthio functionality is essential for the internal olefinic C-H bond to undergo such an alkylation with the O-adjacent C(sp(3))-H bonds of the ethers and the benzylic C-H bonds of the toluene derivatives, respectively. Tetrasubstituted olefins were thus synthesized and further transformed to highly substituted pyrazoles and isoxazoles. The strategy to activate an internal olefinic C-H bond by polarizing its parent olefinic C=C bond with both the dialkylthio group and an electron-withdrawing functionality was investigated. The mechanistic studies suggest a radical pathway for the C(sp(2))-H/C(sp(3))-H cross-coupling reactions. The present protocol provides a convenient route to tetrasubstituted olefins.
34 citations
TL;DR: Iron-promoted difunctionalization of α,α-diaryl and α-aryl-α-alkyl allylic alcohols has been efficiently achieved by means of N-(phenylseleno)phthalimide (N-PSP) under mild conditions.
34 citations
TL;DR: A pincer-type Ru(II)-NNP complex bearing a pyrazolyl-(NH-PtBu2)-pyridine ligand was synthesized and structurally characterized by NMR, IR, elemental analysis, and X-ray single-crystal crystallographic determinations, which efficiently catalyzed the synthesis of multisubstituted pyrroles and pyridines by means of the reactions of secondary alcohols and β- or γ-amino alcohols through deoxygenation and selective C-N and C-C
31 citations
TL;DR: The present protocol provides a promising method to access a stereogenic carbon center bearing both CF3 and organoboron functional groups by means of bis(pinacolato)diboron (B2pin2), affording the enantioenriched products in good yields with high enantioselectivities.
Abstract: Copper-catalyzed borylation of β-trifluoromethyl-α,β-unsaturated ketones was efficiently achieved by means of bis(pinacolato)diboron (B2pin2), affording the enantioenriched products in good yields with high enantioselectivities. CuI and (R,S)-Josiphos consist of the most efficient catalyst system under mild conditions. In the absence of the chiral ligand, the reactions could be performed more efficiently to form β-ketone derivatives which were directly borylated and indirectly trifluoromethylated at the β-carbon atom of the α,β-unsaturated ketone substrates. The present protocol provides a promising method to access a stereogenic carbon center bearing both CF3 and organoboron functional groups.
31 citations
TL;DR: In this article, a diruthenium(II)-NNN complex was assembled through 4,4′-(CH2)3-bipyridine and achieved TOF values up to 1.4 × 107 h-1.
29 citations
TL;DR: Visible-light-induced direct C-H arylation of S,S-functionalized internal alkenes, that is, α-oxo ketene dithioacetals and analogues, has been efficiently realized with aryldiazonium salts as coupling partners and Ru(bpy)3Cl2·6H2O as photosensitizer at ambient temperature.
29 citations
TL;DR: In this paper, a ruthenium(II)-NNN with an unsymmetrical pyrazolyl-pyridylamino pyridine ligand was characterized by NMR, elemental analysis, and X-ray single crystal structural determination.
25 citations
TL;DR: The polarization of the olefinic carbon-carbon double bond by the electron-donating dialkylthio and electron-withdrawing α-oxo functionalities plays a crucial role in making such C-H alkoxylation reactions to occur under mild conditions.
Abstract: Copper-promoted direct C–H alkoxylation of S,S-functionalized internal olefins, that is, α-oxo ketene dithioacetals, was efficiently achieved with alcohols as the alkoxylating agents, (diacetoxyiodo)benzene (PhI(OAc)2) as the oxidant, and benzoquinone (BQ) as the co-oxidant. The alkoxylated olefins were thus constructed and applied for the synthesis of alkoxylated N-heterocycles. The polarization of the olefinic carbon–carbon double bond by the electron-donating dialkylthio and electron-withdrawing α-oxo functionalities plays a crucial role in making such C–H alkoxylation reactions to occur under mild conditions. Mechanistic studies implicate a single-electron-transfer (SET) reaction pathway involved in the overall catalytic cycle.
22 citations
TL;DR: Pincer-type ruthenium(II)-NNN complex catalysts bearing a chiral bis(NHTs)-substituted imidazolyl-oxazolinyl-pyridine ligand were synthesized and structurally characterized by NMR, IR, elemental analysis, and X-ray single-crystal crystallographic determinations.
TL;DR: Bimetallic ruthenium(II) complexes bearing a bis(pyrazolylimidazolylpyridine) ligand bridged by a rotatable single C-C bond or methylene linker were synthesized, structurally characterized, and exhibited diverse catalytic activities for the transfer hydrogenation (TH) reactions of ketones in refluxing isopropyl alcohol.