Cu（I）-Catalyzed Three-Component Coupling of Trifluoromethyl Ketone N-Tosylhydrazones, Alkynes and Azides： Synthesis of Difluoromethylene Substituted 1,2,3-Triazoles

A Cul-catalyzed three-component coupling of trifluoromethyl ketone N-tosylhydrazones, alkynes and azides has been developed. The reaction represents a straightforward method to access difluoromethylene substituted 1,2,3-triazoles. Mechanistically, it has been proposed that the reaction follows a pathway involving the formation of Cu（1） triazolide intermediate, Cu（I） carbene formation, migratory insertion, and β-fluoride elimination. The trans- formation is featured by mild conditions, wide substrate scope and high efficiency.

Visible Light-Promoted Ring-Opening Alkenylation of Cyclic Hemiacetals through β-Scission of Alkoxy Radicals

The chemistry of alkoxy radicals was extensively explored during the period of 1960s to 1990s,but it has remained dormant for the past few decades.Recently,alkoxy radicals attract the attentions again,because new methods for generating alkoxy radical species have emerged.These newly developed methods are mainly based on the photolysis by visible light under mild conditions,thus allowing for new transformations of the carbon-centered radical species that are generated from theβ-scission or hydrogen abstraction of the alkoxy radicals.

Rh（Ⅰ）-Catalyzed Arylation of α-Diazo Phosphonates with Aryl Boronic Acids： Synthesis of Diarylmethylphosphonates

An efficient synthetic method for diarylmethylphosphonates is presented.A series of phosphonate derivatives with diverse functional groups can be accessed via a rhodium catalyzed cross-coupling reaction between a-diazo phosphonates and aryl boronic acids.Migratory insertion of rhodium carbene intermediates is postulated to be the critical step in this transformation.

Palladium-Catalyzed Oxidative Alkynylation of Allenyl Ketones: Access to 3-Alkynyl Poly-substituted Furans

Furans bearing alkynyl substituents are highly useful in organic synthesis.However,the methodologies to access these important furan derivatives are rather limited.We herein report an efficient synthesis of alkynylated furan derivatives based on Pd-catalyzed oxidative cross-coupling reaction between allenyl ketones and terminal alkynes.This novel synthesis of alkynylated furans with wide substrate scope is operationally simple and tolerates various functional groups.Mechanistically,the formation of the palladium carbene through cycloisomerization and the subsequent alkynyl migratory insertion are proposed as the key steps in the transformation.The reaction reported in this paper further demonstrates the generality of the carbene-based cross coupling.

Thermocatalytic Dehydrogenation-Enabled Arene-Alkane Couplings

Comprehensive Summary The direct use of non-prefunctionalized arene and alkane as the starting materials to construct Caryl−Calkyl bond is an unfulfilled target and approaches to this challenge rarely surface in methodology studies.Current methods for thermocatalytic arene-alkane couplings(AAC)occur with specific substrates and/or inconvenient reagents.Herein,we report a one-pot relay bicatalysis system for AAC involving(pincer)Ir-catalyzed alkane transfer dehydrogenation and Fe(OTf)3-catalyzed olefin hydroarylation.This system exhibits broad scope and is particularly effective for alkylation of arenes with arylalkanes to form 1,1-diarylalkanes with high chemo-and regioselectivity,making it potentially useful for late-stage alkylation of complex molecules.Experimental mechanistic data provide a view into the factors controlling the regioselectivity.Finally,the strategy of dehydrogenation-enabled arene-alkane couplings has been successfully extended to a tandem catalysis by using a heterogeneous olefin hydroarylation catalyst.

Co/Fe Dual Catalysis for Sequential Hydrosilylation-Isomerization:Access to Trisubstituted(E)-Alkenyl Silanes from Terminal Alkynes

By rational modification of electronic and steric properties of pincer ligands,a Co/Fe dual catalyst system is developed for one-pot sequential Markovnikov alkyne hydrosilylation and stereoselective alkene isomerization.The protocol provides an atom-economical and efficient approach to trisubstituted(E)-alkenyl silanes from widely accessible terminal alkynes with high regio-and stereoselectivities under mild conditions.The utility of this reaction was demonstrated by gram-scale synthesis and derivatization of bioactive molecules.The radical clock and trapping experiments indicated that radical pathway might be operative in the alkene isomerization step.

Copper Catalyzed Asymmetric [4＋2] Annulations of D-A Cyclobutanes with Aldehydes

Copper catalyzed enantioselective [4＋2] annulations of D-A cyclobutanes and aldehydes have been developed. In the presence of a side arm modified chiral bisoxazoline （SaBOX） ligand, the [4＋2] annulations proceeded smoothly with a broad substrate scope. 22 examples were studied, leading to the corresponding products with various functional groups in 41%-99% yields with 〉99/1 dr and 90%-96% ee. The resulting product with two ester groups was mono-reduced, giving the corresponding product in excellent diastereoselectivity without loss of the enantiopurity.

Copper(I)/Sa BOX catalyzed highly diastereo- and enantio-selective cyclopropanation of cis-1,2-disubstituted olefins with a-nitrodiazoacetates

A copper-catalyzed highly stereoselective cyclopropanation of 1,2-disubstituted olefins with α-nitrodiazo acetates has been developed, giving the desired products in up to 97 % yields, up to 〉99/1 dr and up to 98 % ee, which provides an efficient access to the synthesis of optical active cyclopropane α-amino acids and unnatural α-amino acid derivatives.

Highly enantioselective cyclopropanation of trisubstituted olefins

A highly efficient asymmetric cyclopropanation of trisubstituted olefins with methyl diazoacetate has been developed in terms of an elaborate modified chiral bisoxazoline/copper complex as a catalyst. A broad scope of substrates is compatible with this catalyst system, including various trisubstituted olefins bearing different aryl-, fused aryl-and alkyl-substituents, providing an easy access to optically active 1,1-dimethyl cyclopropanes in good yields with excellent diastereo-and enantio-selectivity.