Homogeneous gold catalysis has experienced extraordinary development since the dawn of this millennium. Oxidative gold catalysis is a vibrant and fertile subfield and has over the years delivered a diverse array of versatile synthetic methods of exceptional value to synthetic practices. This review aims to cover this topic in a comprehensive manner. The discussions are organized by the mechanistic aspects of the metal oxidation states and further by the types of oxidants or oxidizing functional groups. Synthetic applications of oxidative gold catalysis are also discussed. CONTENTS 4.5. Oxidation of Sulfides and Other Functional Groups 9029 5. Conclusion and Outlook 9030 Author Information 9030 Corresponding Author 9030 Authors 9030 Author Contributions 9030 Notes 9030 Biographies 9030 Acknowledgments 9031 References 9031
A cobalt-catalyzed highly Markovnikov-type and enantioselective hydrosilylation of alkenes is developed for the efficient synthesis of valuable chiral dihydrosilanes. This protocol is operationally simple and atom-economy, and using relatively simple and readily available starting materials. The reaction is suitable for both aryl and aliphatic alkenes with excellent functional group tolerability. The reaction could be easily carried out in a gram-scale. The TOF and TON is up to 1800 and 860, respectively.
The asymmetric isomerization of alkyne to allene is the most efficient and the completely atomeconomic approach to this class of versatile axial chiral structure. However, the state-of-the-art is limited to tertbutyl alk-3-ynoate substrates that possess requisite acidic propargylic C-H bonds. Reported here is a strategy based on gold catalysis that is enabled by a designed chiral bifunctional biphenyl-2-ylphosphine ligand. It permits isomerization of alkynes with nonacidic α-C-H bonds and hence offers a much-needed general solution. With chiral propargylic alcohols as substrates, 2,5-disubstituted 2,5-dihydrofurans are formed in one step in typically good yields and with good to excellent diastereoselectivities. With achiral substrates, 2,5-dihydrofurans are formed with good to excellent enantiomeric excesses. A novel center-chirality approach is developed to achieve a stereocontrol effect similar to an axial chirality in the designed chiral ligand. The mechanistic studies established that the precatalyst axial epimers are all converted into the catalytically active cationic gold catalyst owing to the fluxional axis of the latter. Axially chiral allenes are versatile and highly valuable intermediates in asymmetric synthesis. 1 Various preparative methods have been documented. 2 Notwithstanding, the direct isomerization of alkyne to chiral allene, the arguably simplest and the most atom-economic approach, has only been reported with alkynes featuring rather acidic propargylic hydrogens, 3 such as 1,3-diphenylpropyne 3c , f and t-butyl alk-3-ynoates 3d , e , and moreover, high e.e. values are only realized with the latter substrates. To date, there is no asymmetric isomerization of a vast range of other alkynes and especially those devoid of acidic propargylic hydrogens.
Over the past two decades, homogeneous gold catalysis has experienced exponential development and contributed a plethora of highly valuable synthetic methods to the synthetic toolbox. Metalligand cooperative catalysis is a versatile strategy for achieving highly efficient and/or novel catalysis but has seldom been explored in gold chemistry. This minireview summarizes the progress we have made in developing remotely functionalized biaryl-2ylphosphine ligands and employing them in cooperative gold catalysis that achieves excellent catalytic efficiency or realizes previously unknown reactivities. This approach also provides new venues for implementing asymmetric gold catalysis.
A gold(I)‐catalyzed enantioselective dearomatization is achieved via metal‐chiral ligand cooperation. A new and divergent synthesis of chiral bifunctional binaphthyl‐2‐ylphosphines is developed to allow rapid access to these ligands, which in turn facilitate the application of this chemistry to a broad substrate scope including 1‐naphthols, 2‐naphthols, and phenols. Enantiomeric excesses up to 98 % are achieved via selective acceleration of one enantiomer formation enabled by hydrogen bonding between substrate and ligand remote basic group. DFT calculations lend support to the cooperative catalysis and substantiate the reaction stereochemical outcomes.
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