Improving the Catalytic Activity of Au25 Nanocluster by Peeling and Doping

Tuning the nanoclusters＇ compositions and structures is critical for the performance improvement of nanoclusters.Herein,a well-known Au25（SCH2CH2Ph）18 （Au25 for short） nanocluster has been transformed to a rare cadmium doped gold nanocluster [Au13Cd2（PPh3）6（SC2H4Ph）6（NO3）2]2Cd（NO3）4 （Au26Cd5 for short） by peeling and doping.Although Au25 exhibits no catalytic activity toward A3-coupling reaction under the investigated conditions,the novel cadmium doped gold nanocluster Au26Cd5 shows high catalytic activity,as well as good recyclability and substrate tolerance for the same reaction.The high catalytic activity is attributed to the cooperation between the exerted cadmium atoms and the neighbor gold atoms on the surface of Au13 icosahedron.This work has important implication for the tuning of nanoclusters＇ compositions and structures targeting the improvement of catalytic performance by some unusual but effective strategies.

Catalyst-Dependent Direct and Deoxygenative Coupling of Alcohols by Convergent Paired Electrolysis

Developing a general and mild approach to upgrade alcohols into high value products is a hot topic in synthetic chemistry because alcohol is one of the most abundant raw chemicals.Specifically,direct coupling and deoxygenative coupling of alcohols are the two main approaches for the functionalization of alcohols to afford structurally diverse products,and it receives considerable attention.Despite significant advances in the field,there still remains a great challenge to develop a general approach accommodating both coupling reactions,as they commonly involve distinct pathways.Herein,we report an electrochemical approach for the direct coupling and deoxygenative coupling of alcohols with fluorenones.Under paired electrolysis,this catalyst-dependent protocol gives divergent access to diols and tertiary alcohols.Moreover,the synthetic utility of 9H-fluoren-9-ol products has been demonstrated in the synthesis of organic luminophores,phenanthrol,phenanthridine,and amino alcohol.The present approach exhibits some impressive features:(a)catalystdependent selectivity;(b)excellentfunctional-group tolerance(156 examples);(c)mild conditions;and(d)good scalability(∼20 gram scale).

Combined synthesis of interconvertible Au11Cd and Au26Cd5 for photocatalytic oxidations involving singlet oxygen

A novel Au11Cd nanocluster was synthesized by developing a combined method and controlling the kinetics, and another Au26Cd5nanocluster was also obtained after the conditions were changed in the same reaction, which could transfer to Au11Cd in a two-way style. Both alloy nanoclusters can photocatalyze the production of singlet oxygen(1O_(2)) and exhibit enhanced efficiencies in photocatalyzing two kinds of organic oxidations involving singlet oxygen compared with their non-alloyed mother nanoclusters, indicating that the Cd-doping might be an efficient way to enhance the photocatalysis performance of gold nanoclusters and metal nanoclusters are promising photocatalysts for organic oxidation involving singlet oxygen.

Atomically Precise Metal Nanoclusters as Single Electron Transferers for Hydroborylation

The emergence of metal nanoclusters with atomically precise compositions and structures provides an opportunity for in-depth investigation of catalysis mechanisms and structure−property correlations at the nanoscale.However,a serious problem for metal nanocluster catalysts is that the ligands inhibit the catalytic activity through deactivating the surface of the nanoclusters.Here,we introduce a novel catalytic mode for metal nanoclusters,in which the nanoclusters initiate the catalysis via single electron transfer(SET)without destroying the integrity of nanoclusters,providing a solution for the contradiction between activity and stability of metal nanoclusters.We illustrated that the novel activation mode featured low catalyst loading(0.01 mol%),high TOF,mild reaction conditions,and easy recycling of catalyst in alkyne hydroborylation,which often suffered from poor selectivity,low functional group tolerance,etc.Furthermore,the catalyst[Au_(1)Cu_(14)(TBBT)_(12)(PPh_(3))_(6)]^(+)(TBBTH:p-tert-butylthiophenol)can be applied in highly efficient tandem processes such as hydroborylation−deuteration and hydroborylation−isomerization,demonstrating the utility of the introduced activation mode for metal nanoclusters.

Regioselective umpolung addition of dicyanobenzene to α,β-unsaturated alkenes enabled by electrochemical reduction

An umpolung addition of dicyanobenzene toα,β-unsaturated alkenes has been developed using an elec-troreductive strategy.This electrochemical protocol is well compatible with a broad range of convention-ally challenging substrates,includingα,β-unsaturated esters,nitriles and trisubstituted enones.Moreover,good to excellent regioselectivities are observed in the reaction of cinnamates with dicyanobenzene.Synthetic utility of this electrochemical approach is further demonstrated by direct late-stage functionali-zation of(S)-verbenone and 16-dehydropregnenolone acetate.

Aerobic Heterogeneous Palladium-Catalyzed Oxidative Allenic C−H Arylation:Benzoquinone as a Direct Redox Mediator between O_(2)and Pd

Transitionmetal-catalyzedaerobicoxidativereactions using molecular oxygen as the terminal oxidant play a significant role in organic synthesis.Benzoquinone(BQ)has been widely used as an electron-transfer mediator(ETM)in biomimetic palladium-catalyzed aerobic oxidative reactions,but always together with an ETM between O_(2) and BQ,such as a macrocyclic metal complex.Herein,we report on a heterogeneous palladium-catalyzed allenic C(sp3)-H arylation with only catalytic amounts of BQ under air without the need of an additional ETM.Arange ofmultisubstituted 1,3-dienes were synthesized under mild reaction conditions.Mechanistic studies reveal the bifunctional role of BQ as a ligand for reductive elimination and as an ETM between Pd(0)and O_(2).This new regime of oxidation has important implications for further development of other transition metal-catalyzed aerobic oxidative reactions.