Synthesis of Azaheterocycles from Aryl Ketone O-Acetyl Oximes and Internal Alkynes by Cu–Rh Bimetallic Relay Catalysts

A synthetic method for azaheterocycles from aryl ketone O-acetyl oximes and internal alkynes has been developed by using the Cu(OAc)₂–[Cp*RhCl₂]₂ bimetallic catalytic system. The reactions proceeded with both of anti- and syn-isomers of oximes with a wide scope of substituents. The Cu–Rh bimetallic system could be applied for the synthesis of isoquinolines as well as β-carboline, furo[2.3-c]pyridine, pyrrolo[2,3-c]pyridine, and thieno[2,3-c]pyridine derivatives.

Direct Michael Addition of Alkenes via a Cobalt-Dinitrosyl Mediated Vinylic C–H Functionalization Reaction

F. Dean Toste and Robert G. Bergman, JACS, 2011, DOI: 10.1021/ja204564z

Rational Catalysis Design on the Basis of Mechanistic Understanding: Highly Efficient Pd-Catalyzed Cyanation of Aryl Bromides with NaCN in Recyclable Solvents

Rational catalysis design on the basis of a detailed mechanistic understanding has been used to successfully develop the first efficient general Pd-catalyzed aromatic cyanation reaction under the highly sought after practicable conditions: (i) MCN (M = Na or K) as a cyanide source; (ii) low-boiling recyclable solvents; and (iii) minimal quantities of inexpensive, nontoxic promoters. The developed catalytic reaction converts aromatic bromides to the corresponding nitriles in 88–99% isolated yield with NaCN and 0.5–1.0 mol % of a t-Bu₃P-monoligated Pd catalyst in MeCN-THF within 2 h at 70 °C. The process exhibits high functional group tolerance.




Vladimir V. Grushin, JACS, DOI: 10.1021/ja2042035

Organogold Reactivity with Palladium, Nickel, and Rhodium: Transmetalation, Cross-Coupling, and Dual Catalysis

DOI: 10.1021/ar200055y

Recent advances in the gold-catalyzed additions to C–C multiple bonds

Abstract

C–O, C–N and C–C bonds are the most widespread types of bonds in nature, and are the cornerstone of most organic compounds, ranging from pharmaceuticals and agrochemicals to advanced materials and polymers. Cationic gold acts as a soft and carbophilic Lewis acid and is considered one of the most powerful activators of C–C multiple bonds. Consequently, gold-catalysis plays an important role in the development of new strategies to form these bonds in more convenient ways. In this review, we highlight recent advances in the gold-catalyzed chemistry of addition of X–H (X = O, N, C) bonds to C–C multiple bonds, tandem reactions, and asymmetric additions. This review covers gold-catalyzed organic reactions published from 2008 to the present.

Beilstein J. Org. Chem. 2011, 7, 897–936. doi:10.3762/bjoc.7.103

Chlorination and ortho-acetoxylation of 2-arylbenzoxazoles

Efficient and facile catalytic protocols for chlorination and ligand-directed ortho-acetoxylation of 2-arylbenzoxazoles have been developed. The chlorination is not a ligand-directed ortho-functionalization, but an electrophilic substitution process in the benzo ring of the benzoxazole moiety. Meanwhile, the acetoxylation exhibited high regioselectivity for the substrates containing a meta-substituent and occurred at the less sterically hindered ortho-C–H bond of the directing group.

Recyclable Copper Catalyst for meta-Selective CH Bond Arylation

It's a fair cop guvner: The meta-selective arylation of various anilides with diaryliodonium triflates was achieved by using copper oxide nanoparticles imbedded in aluminum oxyhydroxide, Cu/AlO(OH). The copper catalyst is much more reactive than homogeneous Cu^I and Cu^II catalysts; it is also recyclable.

1. Prof. Jaiwook Park, Chem. cat. Chem. 2011,  
DOI: 10.1002/cctc.201100072

Ruthenium-Catalyzed Oxidative Annulation by Cleavage of CH/NH Bonds

Bond activation in action: Unprecedented ruthenium-catalyzed oxidative annulations of alkynes through cleavage of CH bonds set the stage for an efficient 1(2H)-isoquinolone synthesis with ample scope (see scheme; tAm=tert-amyl). Mechanistic studies provided strong evidence for a rate-limiting CH bond metalation through carboxylate assistance.

1. Prof. Dr. Lutz Ackermann, Angew. Chem. Int Ed. 2011, 
DOI: 10.1002/anie.201101943

Simple, Stable, and Easily Accessible Well-Defined CuCF3 Aromatic Trifluoromethylating Agents

Give me an F: Exceptionally easy to make in over 90 % yield (see scheme) and air-stable in the solid state, [(Ph₃P)₃Cu(CF₃)] is a remarkable example of a rarely encountered well-defined Cu(I) trifluoromethylating agent and a convenient starting material for the synthesis of other CuCF₃ complexes, such as [(phen)Cu(PPh₃)(CF₃)].

A Simple and Highly Efficient Iron Catalyst for a [2+2+2] Cycloaddition to Form Pyridines

Joined by iron: The iron catalyst for the formation of pyridines at room temperature (see scheme), which was generated in situ from an inorganic iron salt and a diphosphine ligand, exhibited high reactivity and regioselectivity.

Low Molecular Weight Fluorescent Organogel for Fluoride Ion Detection

The design, synthesis, and the photophysical properties of a Low Molecular Weight Gel (LMWG) based on AB₃ and AB₂ type poly(aryl ether) dendrons with an anthracene chromophore attached through an acylhydrazone linkage are described. The gel is utilized for an efficient ‘naked eye’ detection of fluoride ions (as low as 0.1 equiv with respect to the gelator concentration), through a reversible gel–sol transition, which is associated with a color change from deep yellow to bright red.

DOI: 10.1021/ol201325j

Copper-Catalyzed Oxidative Amination of Benzoxazoles via C−H and C−N Bond Activation: A New Strategy for Using Tertiary Amines as Nitrogen Group Sources

An efficient and conceptually new method for oxidative amination of azoles with tertiary amines via copper-catalyzed C−H and C−N bond activation has been developed. This protocol can be performed in the absence of external base and only requires atmospheric oxygen as oxidant. The catalyst system is very simple and efficient, which opens a new way for using tertiary amines as nitrogen group sources for C−N bond formation reactions.



Org. Lett, 2011, 13, 522

Palladium-Catalyzed C−H Aminations of Anilides with N-Fluorobenzenesulfonimide

The first amide-directed, palladium-catalyzed, intermolecular, highly selective C−H aminations with the non-nitrene-based nitrogen source N-fluorobenzenesulfonimide have been developed. This methodology might provide a new pathway for directed metal-catalyzed aromatic C−H amination.



J. Am. Chem. Soc, 2011, 133, 1694

Rh(III)-Catalyzed Oxidative Coupling of Unactivated Alkenes via C−H Activation

Oxime directed aromatic C−H bond activation and oxidative coupling to alkenes is reported using a cationic Rh(III) catalyst. Significantly, the method can be used to oxidatively couple unactivated, aliphatic alkenes.


Org. Lett. 2011, 540.

Pd/PR3-Catalyzed Cross-Coupling of Aromatic Carboxylic Acids with Electron-Deficient Polyfluoroarenes via Combination of Decarboxylation with sp2 C−H Cleavage

By using Pd(TFA)₂/PCy₃ as a catalyst, a broad range of aromatic carboxylic acids, including heteroaromatic carboxylic acids, efficiently underwent decarboxylative coupling with an array of polyfluoroarenes in the presence of stoichiometric amount of silver salts to generate biaryls. Silver salts were adjusted to the reactivity of aromatic carboxylic acids to efficiently suppress the protodecarboxylation and therefore improve decarboxylative cross-couplings. It was established that the palladium complex containing the PCy₃ ligand was capable of catalyzing the decarboxylation of electron-rich aromatic carboxylic acids, and silver salts promoted the decarboxylation of both electron-rich and -deficient ones. To explain the two different decarboxylation processes, two possible reaction pathways are proposed, which were further supported by the facts that the stoichiometric arylpalladium complex can directly arylate pentafluorobenzene in the presence of PCy₃ and the arylpalladium complex can catalyze the decarboxylative coupling of 2,4-dimethoxybenzoic acid with pentafluorobenzene. The kinetic isotope effect of 4.0 clearly showed that the C−H bond cleavage of polyfluoroarenes is involved in the rate-determining step.

JOC 2011, 76, 882