Bifunctional Ligand Enables Gold-Catalyzed Propargyl C-H Functionalization via Reactive Gold Allenylidene Intermediate.

Gold allenylidene species have been seldom exploited as reactive intermediates in synthetically versatile catalytic reactions. By employing alkynylbenziodoxoles as the substrates and bifunctional WangPhos as the metal ligand, this work demonstrated ready catalytic access to these intermediates of general substitution patterns and their electrophilic reactivities at the γ-carbon center with a diverse range of nucleophiles. The reaction is driven by the reductive decomposition of the benziodoxole moiety and achieves the replacement of a propargylic proton with an N/O/C-based nucleophile, hence realizing reactivity umpolung.

Reactivities of α-Oxo BMIDA Gold Carbenes Generated by Gold-Catalyzed Oxidation of BMIDA-Terminated Alkynes.

An oxidative strategy is reported to access α-oxo BMIDA gold carbenes directly from BMIDA-terminated alkynes. Besides offering expedient access to seldom studied boryl metal carbenes, these BMIDA gold carbene species undergo facile insertions into methyl, methylene, methine, and benzylic C-H bonds in the absence of the Thorpe-Ingold effect. They also undergo efficient OH insertion, cyclopropanation, and F-C alkylations.

Solution structure of a thrombin binding aptamer complex with a non-planar platinum(ii) compound.

Thrombin Binding Aptamer (TBA) is a monomolecular well-defined two G-tetrad antiparallel G-quadruplex DNA that inhibits the activity of human α-thrombin. In this report, we synthesized a quasi-cross-shaped platinum(ii) compound (L'LPt) with one cyclometalated and two carbene ligands. We found L'LPt has selective affinity to bind the TBA G-quadruplex.

BNN-1,3-dipoles: isolation and intramolecular cycloaddition with unactivated arenes.

The mono-base-stabilized 1,2-diboranylidenehydrazine derivatives featuring a 1,3-dipolar BNN skeleton are obtained by dehydrobromination of [ArB(Br)NH] (Ar = 2,6-diphenylphenyl (Dpp), Ar = 2,6-bis(2,4,6-trimethylphenyl)phenyl (Dmp) or Ar = 2,4,6-tri--butylphenyl (Mes*)) with N-heterocyclic carbenes (NHCs). Depending on the Ar substituents, such species can be isolated as a crystalline solid (Ar = Mes*) or generated as reactive intermediates undergoing spontaneous intramolecular aminoboration of the proximal arene rings [3 + 2] cycloaddition (Ar = Dpp or Dmp). The latter reactions showcase the 1,3-dipolar reactivity toward unactivated arenes at ambient temperature.

Incorporation of HO and CO into a BN-embedded 3-3-acephenanthrylene derivative.

A fused tetracyclic BN-species 1 featuring nucleophilic nitrogen and electrophilic boron centers behaves as a reactive N/B frustrated Lewis pair (FLP) for small molecule activation. Specifically, the O-H and C[double bond, length as m-dash]O bonds have been cleaved by 1 with the formation of fused borinic acid 2, borenium species 3, anionic boranuidacarboxylic acid 4 and oxadiazaborolidinone 5, respectively. Quantum-mechanical calculations are conducted to comprehensively understand the activation processes of small molecules by 1.

Unraveling mechanisms of the uncoordinated nucleophiles: theoretical elucidations of the cleavage of bis(-nitrophenyl) phosphate mediated by zinc-complexes with apical nucleophiles.

A theoretical approach was used to investigate the hydrolytic cleavage mechanisms of the bis(-nitrophenyl) phosphate (BNPP) catalyzed by Zn(ii)-complexes featuring uncoordinated nucleophiles. Ligand-based and alternative solvent-based nucleophilic attack reaction models are proposed. The p values of the Zn(ii)-bound water molecules or ligands in the [Zn(L H)(η-HO)(HO)] ( = 1, 2 and 3) complexes, as well as the dimerization tendency of the mononuclear Zn(ii)-complexes, were found to significantly influence the reaction mechanisms.

Hierarchical Gelation of a PdL Metal-Organic Cage Regulated by Cholesteryl Groups.

The creation of supramolecular assemblies by assembly of structurally simple components via supramolecular interactions provides an opportunity to develop functional materials with hierarchical complexibility. Herein, we report an assembly approach to supramolecular gels based on metal-organic cages with tunable hierarchical structures and properties. A Pd cage ( is cholesteryl-functionalized 3,5-bis(4-pyridyl)benzene) bearing 24 cholesteryl groups is used as a supramolecular building unit and molecular platform for functionalization with tunable functional behaviors.

Mechanism of Hypervalent Iodine Promoted Fluorocyclization of Unsaturated Alcohols: Metathesis via Double Acids Activation.

Lewis/Bronsted acid activation plays a key role in hypervalent iodine reagent-mediated reactions. In addition to generally accepted cis-activation or trans-activation, this study reveals another important Lewis/Bronsted acid activation mode, the double-activation. Different from the generally proposed iodine(III)iranium S2 mechanism, the hypervalent difluoro-iodoarene-promoted fluorocyclization of unsaturated alcohol prefers to undergo the metathesis mechanism via an iodine(III)-π intermediate.

Ruthenium-Catalyzed Direct Synthesis of Semisaturated Bicyclic Pyrimidines via Selective Transfer Hydrogenation.

A new ruthenium-catalyzed direct and selective synthesis of semisaturated bicyclic pyrimidines, from α-aminopyridyl alcohols and nitriles, has been demonstrated. The synthesis proceeds with an easily available catalyst system, broad substrate scope, excellent functional tolerance, and no need for high pressure H gas. Control experiments indicate that the reaction proceeds via successive dehydrogenative annulation and transfer hydrogenation of the less electrophilic pyridyl nucleus, and the density functional theory (DFT) study reveals the origin of such a unique selectivity.

Merging Distal Alkynyl Migration and Photoredox Catalysis for Radical Trifluoromethylative Alkynylation of Unactivated Olefins.

Disclosed herein is a novel, redox-neutral protocol for the visible-light-induced radical alkynylation of unactivated olefins. The intramolecular migration of an alkynyl group, by cleaving an inert C-C σ bond, is realized for the first time. A wide range of synthetically useful trifluoroethylated linear alkynes are readily obtained under mild reaction conditions.

Rationalization of the selectivity between 1,3- and 1,2-migration: a DFT study on gold(i)-catalyzed propargylic ester rearrangement.

Gold catalyzed rearrangement of propargylic esters can undergo 1,3-acyloxy migration to form allenes, or undergo 1,2-acyloxy migration to access gold-carbenoids. The variation in migration leads to different reactivities and diverse cascade transformations. The effect of terminal substituents is very important for the rearrangement.

Copper-Catalyzed Regioselective C-H Sulfonylation of 8-Aminoquinolines.

Copper(I)-catalyzed 5-sulfonation of quinolines via bidentate-chelation assistance has been developed. The reaction is compatible with a wide range of quinoline substrates and arylsulfonyl chlorides. Experimental and theoretical (DFT) investigation implicated that a single-electron-transfer process is involved in this sulfonylation transformation.

Unusual non-bifunctional mechanism for Co-PNP complex catalyzed transfer hydrogenation governed by the electronic configuration of metal center.

The mimic of hydrogenases has unleashed a myriad of bifunctional catalysts, which are widely used in the catalytic hydrogenation of polar multiple bonds. With respect to ancillary ligands, the bifunctional mechanism is generally considered to proceed via the metal-ligand cooperation transition state. Inspired by the interesting study conducted by Hanson et al.

The effect of HSAB on stereoselectivity: copper- and gold-catalyzed 1,3-phosphatyloxy and 1,3-halogen migration relay to 1,3-dienes.

The origin of stereodivergence between copper- and gold-catalyzed cascade 1,3-phosphatyloxy and 1,3-halogen migration from α-halo-propargylic phosphates to 1,3-dienes is rationalized with density functional theory (DFT) studies. Our studies reveal the significant role of the relative hardness/softness of the metal centers in determining the reaction mechanism and the stereoselectivity. The relative harder Cu(I/III) center prefers an associative pathway with the aid of a phosphate group, leading to the (Z)-1,3-dienes.