Unusual Kinetics Induced by Ligands in Rhodium(III)-Catalyzed Dehydrogenative Olefination Reactions.

In this study, we investigate the effects of ligands on C-H activation during rhodium(III)-catalyzed C-H bond olefination reactions using well-defined [CpRh] catalytic systems with three representative Cp (Cp (η-CH), Cp (η-CMeCF), and Cp* (η-CMe)) ligands. Our results demonstrate that C-H activation as the rate-limiting step is significantly influenced by the steric properties of the Cp ligands. Moreover, we observe a dramatic acceleration of the simple [CpRh]-catalyzed C-H olefination reaction with acid coproducts such as HOAc, implying an autocatalytic C-H activation process.

Cyclometalated Platinum(II) Metallomesogens Based on Half-Disc-Shaped β-Diketonate Ligands with Hexacatenar: Crystal Structures, Mesophase Properties, and Semiconductor Devices.

A series of new half-disc-shaped platinum(II) complexes [Pt(ppy)(AL-6OCH)] (, [Pt(ppyF)(AL-6OCH)] (, and [Pt(ppyCF)(AL-6OCH)] ( (AL-6OCH = 1,3-bis(3,4,5-trialkoxyphenyl)propane-1,3-dionato; = 1, 6, 12) with concise structures have been designed and synthesized, in which 2-phenylpyridine (ppy) derivatives were used as cyclometalated ligands and hexacatenar β-diketonate derivatives AL-6OCH as auxiliary ligands. The single-crystal data of the methoxy diketonate analogues , , and indicate that they all display excellent square planarity. These platinum(II) complexes show a certain emission tunability (ranging from λ = 506-535 nm) by the introduction of fluorine or trifluoromethyl into ppy.

Extension of the Simmons-Smith reaction to metal-carbynes: efficient synthesis of metallacyclopropenes with σ-aromaticity.

The Simmons-Smith reaction offers a direct route for conversion of an alkene into a cyclopropane with a zinc carbenoid as the active intermediate. Zinc carbenoids, however, have never delivered a methylene unit to substrates with metal-carbon multiple bonds. Herein, we describe this type of reaction and the construction of three-membered rings has now been applied in organometallic systems by combining classical zinc carbenoid reagents with a range of structurally and electronically diverse metal carbynes.

Trisulfur radical anion-triggered stitching thienannulation: rapid access to largely π-extended thienoacenes.

Largely π-extended rylene diimide-fused thienoacenes, a new family of fully fused electron donor-acceptor (D-A) molecules, have been readily synthesized by a novel trisulfur radical anion (S˙)-triggered stitching thienannulation strategy. The ladder-type fused thiophene cores are constructed in a stitching manner through multiple carbon-sulfur bond formation between acetylenic rylene dyes and S˙. A detailed mechanistic study of these stitching thienannulations unveiled the multiple reactivities of S˙.

Scalable Rhodium(III)-Catalyzed Aryl C-H Phosphorylation Enabled by Anodic Oxidation Induced Reductive Elimination.

Transition metal catalyzed C-H phosphorylation remains an unsolved challenge. Reported methods are generally limited in scope and require stoichiometric silver salts as oxidants. Reported here is an electrochemically driven Rh -catalyzed aryl C-H phosphorylation reaction that proceeds through H evolution, obviating the need for stoichiometric metal oxidants.

Isolation of an Eleven-Atom Polydentate Carbon-Chain Chelate Obtained by Cycloaddition of a Cyclic Osmium Carbyne with an Alkyne.

Carbon ligands have long played an important role in organometallic chemistry. However, previous examples of all-carbon chelating ligands are limited. Herein, we present a novel complex with an eleven-atom carbon chain as a polydentate chelating ligand.

Efficient endo Cycloisomerization of Terminal Alkynols Catalyzed by a New Ruthenium Complex with 8-(Diphenylphosphino)quinoline Ligand and Mechanistic Investigation.

Several new ruthenium complexes supported by the P,N-donor ligand 8-(diphenylphosphino)quinoline (DPPQ) were synthesized, including [RuCl (DPPQ) ] (1), [Ru(μ-Cl)(DPPQ) ] (BPh ) (2), and [RuCl(DPPQ) Py](BF ) (3). Complex 2, with only 1 mol % loading, was found to be catalytically active for the endo cycloisomerization of various terminal alkynols to endo-cyclic enol ethers in moderate to excellent yields. In particular, the 7- and 8-endo heterocyclization can be achieved efficiently to give the seven-membered 3-benzoxepine and eight-membered 3-benzo[d]oxocine derivatives.

Rhodium-Catalyzed β-Selective Oxidative Heck-Type Coupling of Vinyl Acetate via C-H Activation.

An efficient Rh(III)-catalyzed direct ortho-C-H olefination of acetanilides with vinyl acetate was developed. This protocol provides a straightforward pathway to a series of (E)-2-acetamidostyryl acetates, giving access to indole derivatives following a simple hydrolysis/cyclization process.

Synthesis of α-Aminonaphthalenes via Copper-Catalyzed Aminobenzannulation of (o-Alkynyl)arylketones with Amines.

A copper-catalyzed aminobenzannulation of (o-alkynyl)arylketones with amines has been developed. This method features the use of a cheap copper catalyst, the facile annulation involving various amines, and the good functional group tolerance.

Copper-Catalyzed Direct C2-Benzylation of Indoles with Alkylarenes.

The copper-catalyzed regioselective cross-dehydrogenative coupling of N-pyrimidylindoles with benzylic C(sp(3))-H bonds has been developed. Di-tert-butyl peroxide was employed as a mild oxidant, and benzaldehyde proved to be an effective additive. This reaction provides a direct and pratical route to a variety of 2-benzylindoles.

Correction: Silver-mediated direct phosphorylation of benzothiazoles and thiazoles with diarylphosphine oxides.

Correction for 'Silver-mediated direct phosphorylation of benzothiazoles and thiazoles with diarylphosphine oxides' by Hui-Jun Zhang et al., Chem. Commun.

Highly Active Gold(I)-Silver(I) Oxo Cluster Activating sp³ C-H Bonds of Methyl Ketones under Mild Conditions.

The activation of C(sp(3))-H bonds is challenging, due to their high bond dissociation energy, low proton acidity, and highly nonpolar character. Herein we report a unique gold(I)-silver(I) oxo cluster protected by hemilabile phosphine ligands [OAu3Ag3(PPhpy2)3](BF4)4 (1), which can activate C(sp(3))-H bonds under mild conditions for a broad scope of methyl ketones (RCOCH3, R = methyl, phenyl, 2-methylphenyl, 2-aminophenyl, 2-hydroxylphenyl, 2-pyridyl, 2-thiazolyl, tert-butyl, ethyl, isopropyl). Activation happens via triple deprotonation of the methyl group, leading to formation of heterometallic Au(I)-Ag(I) clusters with formula RCOCAu4Ag4(PPhpy2)4(BF4)5 (PPhpy2 = bis(2-pyridyl)phenylphosphine).

Rh/Cu-catalyzed multiple C-H, C-C, and C-N bond cleavage: facile synthesis of pyrido[2,1-a]indoles from 1-(pyridin-2-yl)-1H-indoles and γ-substituted propargyl alcohols.

An unusual Rh/Cu-catalyzed synthesis of pyrido[2,1-a]indoles starting from 1-(pyridin-2-yl)-1H-indoles and γ-substituted propargyl alcohols was presented. The multi-step cascade transformations formally involve the cleavage of two C-H, three C-C, and one C-N bonds with concomitant construction of two C-H, four C-C, and one C-N bonds with excellent chemoselectivity in one-pot reaction.

Silver-mediated direct phosphorylation of benzothiazoles and thiazoles with diarylphosphine oxides.

A silver nitrate-mediated, efficient phosphorylation of benzothiazoles and thiazoles with diarylphosphine oxides was developed. This process provides a convenient route for the synthesis of a variety of 2-diarylphosphoryl benzothiazoles and thiazoles which are promising precursors of a series of hemilabile P,N-ligands with small bite angles.

Rh(III)-Catalyzed Oxidative Coupling of Benzoic Acids with Geminal-Substituted Vinyl Acetates: Synthesis of 3-Substituted Isocoumarins.

The Rh(III)-catalyzed C-H activation initiated cyclization of benzoic acids with electron-rich geminal-substituted vinyl acetates was described. The reaction was employed to prepare a range of 3-aryl and 3-alkyl substituted isocoumarins selectively.

A half-sandwich 1,2-azaborolyl ruthenium complex: synthesis, characterization, and evaluation of its catalytic activities.

A half-sandwich 1,2-azaborolyl (Ab) ruthenium complex, (Ab-C≡CPh)RuCl(PPh3)2 (1), has been synthesized by treating RuCl2(PPh3)3 with lithium 1,2-azaborolide L-1, or by treating either RuCl2(PPh3)3 or RuHCl(PPh3)3 directly with 1,2-azaborole LH-1. It is evaluated as a suitable precatalyst in [2 + 2] cycloadditions of norbornene derivatives with DMAD and in atom transfer radical additions of halogenated compounds with olefins.

From osmium hydrido vinylidene to osmacycles: the key role of osmabutadiene intermediates.

Osmium hydrido vinylidene 1 shows diverse cyclization reactivity with activated terminal alkynes. Treatment of 1 with HC≡CCOR' (R'=OEt and Me) gave osmafurans 3a and 3b via osmium alkenyl/vinylidenes 2a and 2b. In addition, 1 reacted with HC≡CCH(OH)C≡CH to yield osmabenzene 4, in which the alkynol acted as a C(5) fragment to cyclize with 1.

A rhodamine-deoxylactam based sensor for chromo-fluorogenic detection of nerve agent simulant.

N-(rhodamine B)-deoxylactam-5-amino-1-pentanol (dRB-APOH) was designed and prepared as the chromo-fluorogenic sensor for detection of a nerve agent simulant via analyte triggered tandem phosphorylation and opening of the intramolecular deoxylactam. The successful detection of diethyl chlorophosphate suggests the utility of rhodamine-deoxylactams as the chromo-fluorogenic signal reporting platform for design of sensors targeting reactive chemical species via various chemistries.

Electrophilic substitution reactions of metallabenzynes.

The electrophilic substitution reactions of metallabenzynes Os(≡CC(R)═C(CH(3))C(R)═CH)Cl(2)(PPh(3))(2) (R = SiMe(3), H) were studied. These metallabenzynes react with electrophilic reagents, including Br(2), NO(2)BF(4), NOBF(4), HCl/H(2)O(2), and AlCl(3)/H(2)O(2) to afford the corresponding bromination, nitration, nitrosation, and chlorination products. The reactions usually occur at the C2 and C4 positions of the metallacycle.

pH-switchable inversion of the metal-centered chirality of metallabenzenes: opposite stereodynamics in reactions of ruthenabenzene with L- and D-cysteine.

We report herein the first study on the chemical interaction between metallabenzenes and bioactive molecules. Due to its unique stereoelectronic activities, a phenanthroline-derived ruthenabenzene [Ru{CHC(PPh(3))CHC(PPh(3))CH}Cl(C(12)H(8)N(2))(PPh(3))]Cl(2) (1) selectively binds cysteine in aqueous solution at physiological pH and then undergoes a dynamic inversion of configuration at the Ru center. The structure of the L-cysteine-binding product of 1 has been determined by means of X-ray diffraction.

Visual and fluorogenic detection of a nerve agent simulant via a Lossen rearrangement of rhodamine-hydroxamate.

A visual and fluorogenic detection method for a nerve agent simulant was developed based on a Lossen rearrangement of rhodamine-hydroxamate, in the presence of diethyl chlorophosphate, under alkaline conditions.

Selective and efficient cycloisomerization of alkynols catalyzed by a new ruthenium complex with a tetradentate nitrogen-phosphorus mixed ligand.

The new ruthenium complex [Ru(N(3)P)(OAc)][BPh(4)] (4), in which N(3)P is the N,P mixed tetradentate ligand N,N-bis[(pyridin-2-yl)methyl]-[2-(diphenylphosphino)phenyl]methanamine was synthesized. The complex was found to be catalytically active for the endo cycloisomerization of alkynols. The catalytic reactions can be used to synthesize five-, six-, and seven-membered endo-cyclic enol ethers in good to excellent yields.

Nucleophilic aromatic addition reactions of the metallabenzenes and metallapyridinium: attacking aromatic metallacycles with bis(diphenylphosphino)methane to form metallacyclohexadienes and cyclic eta(2)-allene-coordinated complexes.

The reactions of phosphonium-substituted metallabenzenes and metallapyridinium with bis(diphenylphosphino)methane (DPPM) were investigated. Treatment of [Os{CHC(PPh(3))CHC(PPh(3))CH}Cl(2)(PPh(3))(2)]Cl with DPPM produced osmabenzenes [Os{CHC(PPh(3))CHC(PPh(3))CH}Cl(2){(PPh(2))CH(2)(PPh(2))}]Cl (2), [Os{CHC(PPh(3))CHC(PPh(3))CH}Cl{(PPh(2))CH(2)(PPh(2))}(2)]Cl(2) (3), and cyclic osmium eta(2)-allene complex [Os{CH=C(PPh(3))CH=(eta(2)-C=CH)}Cl(2){(PPh(2))CH(2)(PPh(2))}(2)]Cl (4). When the analogue complex of osmabenzene 1, ruthenabenzene [Ru{CHC(PPh(3))CHC(PPh(3))CH}Cl(2)(PPh(3))(2)]Cl, was used, the reaction produced ruthenacyclohexadiene [Ru{CH=C(PPh(3))CH=C(PPh(3))CH}Cl{(PPh(2))CH(2)(PPh(2))}(2)]Cl(2) (6), which could be viewed as a Jackson-Meisenheimer complex.

Dimethyl (E)-2-(N-phenyl-acetamido)-but-2-enedioate.

The title compound, C(14)H(15)NO(5), was obtained from the reaction of acetanilide with dimethyl acetyl-enedicarboxyl-ate in the presence of potassium carbonate. The C=C double bond adopts an E configuration and the geometry around the amide N atom is almost planar rather than pyramidal (mean deviation of 0.0032 Å from the C(3)N plane).