A general protocol for the synthesis of N-alkyl indoles has been developed via a redox neutral C–H activation strategy using a traceless nitroso directing group. A broad scope of substituted N-alkyl ...indoles has been prepared in good to excellent yields using a very simple Rh catalyst system in the absence of an external oxidant or any other additive. Good to excellent regioselectivity has been achieved for asymmetrically disubstituted acetylenes.
Unprotected indoles are prepared with the title method, which has a wide scope for alkynes. Excellent regioselectivity was accomplished for aryl–alkyl and alkyl–alkyl disubstituted acetylenes. This ...reaction features an unusual 1,2 rhodium migration and ring‐contraction‐triggered NN bond cleavage. It allows rapid conversion of the reaction products into several functional molecules.
The development of catalysts with high activity and durability for the cathodicoxygen reduction reaction （ORR） in both alkaline and acidic media is importantfor improving the performance of the ...proton exchange membrane （PEM） fuelcells. This can be achieved by dispersing Pt-based alloy nanoparticles insideN-doped porous carbon frameworks. However, it still requires the developmentof a facile method towards synthesizing this unique hybrid structure. In this work,we demonstrate that N-doped carbon-stabilized PtCo nanoparticles （PtCo@NC）can be facilely synthesized via thermal decomposition of Pt-incorporatedCo-based zeolitic imidazolate framework （Pt@ZIF-67）. The thickness of the carbonframework can be optimized to enable excellent durability, in sharp contrastto a commercial Pt/C catalyst. The mass activities achieved by optimizing thethickness of the carbon framework are 0.80 and 0.82 A-mg^-1, at 0.9 V vs. RHE inalkaline and acidic electrolytes, respectively, which are nearly 8 times greaterthan those of the Pt/C. This work provides an alternative approach to low-costand high-verformance catalvsts for both alkaline and acidic fuel cells.
Surface charge state plays an important role in tuning the catalytic performance of nanocrystals in various reactions. Herein, we report a synthetic approach to unique Pt–Pd–graphene stack structures ...with controllable Pt shell thickness. These unique hybrid structures allow us to correlate the Pt thickness with performance in the hydrogen‐evolution reaction (HER). The HER activity increases with a decrease in the Pt thickness, which is well explained by surface polarization mechanism as suggested by first‐principles simulations. In this hybrid system, the difference in work functions of Pt and Pd results in surface polarization on the Pt surface, tuning its charge state for hydrogen reduction. Meanwhile, the supporting graphene provides two‐dimensional channels for efficient charge transport, improving the HER activities. This work opens up possibilities of reducing Pt usage while achieving high HER performance.
Less is more: Pt–Pd–graphene stack structures (see picture) are prepared by a new method that allows control of the thickness of the Pt shell. This thickness correlates with performance in the hydrogen evolution reaction (HER). As a result of surface polarization, the HER activity actually increases with decreasing Pt thickness, opening possibilities of using less Pt.
A metal–semiconductor–metal ternary hybrid structure with two well‐designed interfaces is developed to synergize a Schottky junction with the plasmonic effect. The designed hybrid structure exhibits ...dramatically enhanced performance in full‐spectrum photocatalysis.
A quaternary carbon center containing an oxindole motif is constructed via NHC-catalyzed transition-metal and aldehyde-free intermolecular Heck-type alkyl radical addition initiated annulation. This ...redox-neutral protocol also features a simple procedure, broad substrate scope, good functional group tolerance and could be smoothly amplified to a gram scale. The mechanism study shows that the reaction possibly undergoes two folds of SET processes with an NHC radical cation intermediate involved.
PtFeCo alloy nanostructures in a TriStar shape with tunable Fe and Co content are developed for the electrocatalytic hydrogen evolution reaction (HER). With electronic and surface structures ...well‐tailored, the PtFeCo nanostructures exhibit dramatically enhanced performance in HER against commercial Pt/C and other Pt‐based nanoparticles.
Solar CO2 reduction efficiency is largely limited by poor photoabsorption, sluggish electron–hole separation, and a high CO2 activation barrier. Defect engineering was employed to optimize these ...crucial processes. As a prototype, BiOBr atomic layers were fabricated and abundant oxygen vacancies were deliberately created on their surfaces. X‐ray absorption near‐edge structure and electron paramagnetic resonance spectra confirm the formation of oxygen vacancies. Theoretical calculations reveal the creation of new defect levels resulting from the oxygen vacancies, which extends the photoresponse into the visible‐light region. The charge delocalization around the oxygen vacancies contributes to CO2 conversion into COOH* intermediate, which was confirmed by in situ Fourier‐transform infrared spectroscopy. Surface photovoltage spectra and time‐resolved fluorescence emission decay spectra indicate that the introduced oxygen vacancies promote the separation of carriers. As a result, the oxygen‐deficient BiOBr atomic layers achieve visible‐light‐driven CO2 reduction with a CO formation rate of 87.4 μmol g−1 h−1, which was not only 20 and 24 times higher than that of BiOBr atomic layers and bulk BiOBr, respectively, but also outperformed most previously reported single photocatalysts under comparable conditions.
BiOBr atomic layers with abundant oxygen vacancies were synthesized. The photoresponse of BiOBr extends into the visible range, while charge delocalization around the vacancies contributes to CO2 conversion into COOH*. The material catalyzes visible‐light‐driven CO2 reduction with a CO formation rate of 87.4 μmol g−1 h−1, which is 20 and 24 times greater than that of BiOBr atomic layers and bulk BiOBr, respectively.
A mild, aerobic, catalytic process for obtaining nitriles directly from alcohols and aqueous ammonia is described. The reaction proceeds via a dehydrogenation cascade mediated by catalytic CuI, bpy, ...and TEMPO in the presence of O2. The substrate scope is broad including various functionalized aromatic and aliphatic alcohols. This protocol enabled the one-pot synthesis of various biaryl heterocycles directly from commercially available alcohols.
Diverse opportunities: A Rhodium(III)‐catalyzed ortho‐selective olefination of arenes using a novel triazene as a directing group is reported. This method exhibits substantial post‐functionalization ...synthetic versatility, overcoming a vital limitation in C sp 2H activation/functionalization products: restricted structural diversity.
