Progress in Diazo Compounds Mediated Transition-Metal-Catalyzed C—H Alkylation

Abstract

Diazo compounds had been widely employed as a class of environment friendly and highly efficient coupling reagents in transition-metal-catalyzed C-H bonds insertion reactions. Recently, C-H alkylation of various arenes and heteroarenes has been achieved enormous successes using diazo compounds as the alkylation reagents under a new catalytic model. The recent progress in diazo compounds mediated transition-metal-catalyzed C-H alkylation and tandem C-H alkylation/cyclization is reviewed, including reaction mechanism and synthetic applications. Furthermore, the prospects of this reaction are also discussed.

Sub-nanometer-thick AI2O3 Overcoat Remarkably Enhancing Thermal Stability of Supported Gold Catalysts

“…respectively ( Fig.1 (b) and (c)), consistent with previous observation [13]. Applying TiO 2 overcoating onto the Au/TiO 2 catalyst by ALD at 150 • C would not change the Au particle size, indicated by Fig.1(d) [34]. The insert of Fig.1(d) shows that the thickness of TiO 2 overcoat on 50cTi-Au/TiO 2 was about 1.5 nm, which indicates the growth rate of TiO 2 ALD was about 0.3Å/cycle, consistent with reports in Ref.…”

“…Biener et al demonstrated that an Al 2 O 3 film grown by ALD with even 1 nm thickness can stabilize the nanoporous bulk gold up to 1000 • C, much more sufficient than an 2 nm thick TiO 2 overcoat grown by ALD which can stabilize the nanoporous bulk gold up to 600 • C [33]. We recently demonstrated that TiO 2 ALD overcoat on Au/Al 2 O 3 catalyst significantly improved the CO oxidation activity, where we found that TiO 2 overcoat was preferentially grown at the low-coordination sites of Au nanoparticles [34]. However, applying TiO 2 and Al 2 O 3 ALD overcoat onto supported Au catalysts for improving thermal stability of Au nanoparticles has not been reported.…”

“…TiO 2 ALD overcoating on Au/TiO 2 catalysts was performed in a viscous flow reactor (GEMSTAR-6TM Benchtop ALD, Arradiance) at 150 • C by alternatively exposing titanium isopropoxide (TTIP, 99.7%, Sigma-Aldrich) and Millipore water for different ALD cycles. The TTIP precursor was heated to 80 • C to get a reasonable vapor pressure, while the water source was kept at room temperature [34]. The timing sequence of TiO 2 ALD was 10, 200, 8, and 250 s for TTIP exposure, N 2 purge, water exposure, and N 2 purge, respectively.…”

“…Subsequently, the sample was exposed to 10% CO in He at a flow rate of 20 mL/min for about 15 min until saturation. In order to avoid any variations caused by the decline of CO chemisorption peak during He purge [34], here we collected the DRIFT spectra of all samples during the flow of 10% CO in He. The CO chemisorption spectra were obtained by subtracting the CO chemisorption DRIFT spectrum of TiO 2 to remove the gas phase CO. All DRIFT spectra were collected with 256 scans at a resolution of 4 cm −1 .…”

Current Researches and Applications of Azole-BasedSupermolecules as Medicinal Agents

“…磺胺以及 N-取代的衍生物在抗细菌方面有广泛应 用 [279,280] . [285] , 尤其是通过吡唑环构筑的新型抗菌络合物超分 子, 受到特别关注, 成为抗菌药物开发的新方向 [286,287] .…”