How Can Theory Predict the Selectivity of Palladium-Catalyzed Cross-Coupling of Pristine Aromatic Molecules?

Abstract

The new approach for palladium-catalyzed cross-coupling of two non-activated aromatic compounds (D. R. Stuart, K. Fagnou, Science2007, 316, 1172) was studied theoretically. The energetic span model (S. Kozuch, S. Shaik, Acc. Chem. Res.2011, 44, 101, and references therein) was employed to analyze the kinetic behavior of the catalytic cycle. The computed energy profile, combined with the energetic span model, accounts for the experimental selectivity, which favors the hetero-coupling of benzene with indole. This selectivity is driven by a fine balance of the entropic contributions and the high ratio of concentrations used for benzene over indole. This analysis may allow future theoretical predictions of how different aromatic compounds can be effectively coupled.

Investigating N-methoxy-N′-aryl ureas in oxidative C–H olefination reactio: an unexpected oxidation behaviour

Abstract:

Herein, we report a urea derived directing group for mild and highly selective oxidative C–H bond olefination. Subsequent intramolecular Michael addition affords dihydroquinazolinones in good yields. The N–O bond of the urea substrate exhibits superior oxidative behaviour compared to a variety of other external oxidants.

Frank Glorius, Org. Biomol. Chem, 2011, 9, 4736

Cobalt–Phenanthroline Catalysts for the ortho Alkylation of Aromatic Imines under Mild Reaction Conditions

Mild mannered: Cobalt catalysts complexed with phenanthroline-type ligands and activated with Grignard reagents serve as inexpensive and effective catalysts for the ortho alkylation of aromatic imines with a variety of olefins (see scheme). The new catalytic systems feature remarkably mild reaction conditions for CH bond activation and functionalization.

Prof. Naohiko Yoshikai, Angew. Chem Int. Ed, 2011, 

DOI: 10.1002/anie.201101823

A Metal-Free Route to 2-Aminooxazoles by Taking Advantage of the Unique Ring Opening of Benzoxazoles and Oxadiazoles with Secondary Amines

A Metal-Free Route to 2-Aminooxazoles by Taking Advantage of the Unique Ring Opening of Benzoxazoles and Oxadiazoles with Secondary Amines

Toss an amine into the ring: A new metal-free protocol for the amination of oxazoles has been developed by using iodobenzene diacetate to couple various oxazoles with amines (see scheme). The reaction proceeds through a ring-opening and subsequent ring-closing pathway. The optimal conditions are very mild and the substrate scope is broad, producing a range of 2-aminooxazoles, an important pharmacophore with high bioactivity.

 Prof. Dr. Sukbok Chang, Chemistry, 2011, DOI: 10.1002/chem.201100910

RhIII-Catalyzed Oxidative Olefination of Vinylic C[BOND]H Bonds: Efficient and Selective Access to Di-unsaturated α-Amino Acid Derivatives and Other Linear 1,3-Butadienes

RhIII-Catalyzed Oxidative Olefination of Vinylic C[BOND]H Bonds: Efficient and Selective Access to Di-unsaturated α-Amino Acid Derivatives and Other Linear 1,3-Butadienes

Olefin(s) get-together! A Rh^III-catalyzed oxidative cross-coupling of different olefins was developed, resulting in the formation of valuable linear butadiene products and especially di-unsaturated α-amino acid derivatives. 1,1-Di-, 1,2-di-, and 1,1,2-trisubstituted olefins could be coupled with styrenes and acrylates. In these reactions, remarkably high levels of chemo-, regio-, and stereoselectivity were obtained, rendering this a valuable synthetic tool.

Ruthenium-Catalyzed Direct C–H Bond Arylations of Heteroarenes - Organic Letters (ACS Publications)

Ruthenium-Catalyzed Direct C–H Bond Arylations of Heteroarenes

Ruthenium-catalyzed C–H bond arylations of indoles, thiophenes, and pyrroles were accomplished in a highly chemo- and site-selective manner through the use of removable directing groups.

Lutz Ackermann and Alexander V. Lygin, Org. Lett., 2011, DOI: 10.1021/ol2010648

Consecutive Condensation, C–N and N–N Bond Formations: A Copper- Catalyzed One-Pot Three-Component Synthesis of 2H-Indazole

Consecutive Condensation, C–N and N–N Bond Formations: A Copper- Catalyzed One-Pot Three-Component Synthesis of 2H-Indazole

Abstract

2H-Indazoles are synthesized using copper-catalyzed, one-pot, three-component reactions of 2-bromobenzaldehydes, primary amines, and sodium azide. A copper catalyst plays the key role in the formation of C–N and N–N bonds. This method has a broad substrate scope with a high tolerance for a variety of functional groups.

CuI-catalyzed Suzuki coupling reaction of organoboronic acids with alkynyl bromides

ScienceDirect - Tetrahedron : CuI-catalyzed Suzuki coupling reaction of organoboronic acids with alkynyl bromides:

Abstract A CuI-catalyzed Suzuki cross-coupling reaction of organoboron derivatives with alkynyl bromides has been developed. In the presence of CuI (10 mol %) and 8-hydroxyquinoline (20 mol %), organoboron derivatives including aromatic and alkenyl boronic acids, potassium aryltrifluoroborates, and sodium tetraphenylborate reacted smoothly with 1-bromo-2-substituted acetylene to generate the corresponding cross-coupling products in good to excellent yields in C2H5OH. It is important to note that aromatic N,O-ligand 8-hydroxyquinoline is the most effective ligand for the reaction.

Copper-Catalyzed Intramolecular Dehydrogenative Aminooxygenation: Direct Access to Formyl-Substituted Aromatic N-Heterocycles

A direct synthesis of carbaldehydes through intramolecular dehydrogenative aminooxygenation has been developed. The process uses a catalytic amount of copper(II) in DMF or DMA under oxygen and does not require additional oxidants (see scheme). Mechanistic studies suggest that the carbonyl oxygen atom of the aldehyde is derived from oxygen through a copper-mediated oxygen activation process via a peroxy–copper(III) intermediate.

Angew. Chem. Int. Ed, 2011. DOI: 10.1002/anie.201100362

Removable Directing Groups in Organic Synthesis and Catalysis

Abstract

Directing groups have been widely used in recent years to achieve control over all aspects of reaction selectivity in a wide range of transformations involving transition-metal catalysis and organometallic reagents. In cases when the existing functional group within a substrate is unsuited to achieve efficient intramolecular delivery of a reagent or catalyst, the specific introduction of an appropriately designed removable reagent-directing group can be a solution to this problem. In this Review we give an overview of the state of the art in this area, including the stoichiometric and catalytic use of directing groups.

1. Dr. Géraldine Rousseau, 
2. Prof. Dr. Bernhard Breit, Angew. Chem. Int. Ed, 2011

1. DOI: 10.1002/anie.201006139

CH Bonds Could Talk: Selective CH Bond Oxidation

Abstract

CH oxidation has a long history and an ongoing presence in research at the forefront of chemistry and interrelated fields. As such, numerous highly useful articles and reviews have been written on this subject. Logically, these are generally written from the perspective of the scope and limitations of the reagents employed. This Minireview instead attempts to emphasize chemoselectivity imposed by the nature of the substrate. Consequently, many landmark discoveries in the field of CH oxidation are not discussed, but hopefully the perspective taken herein will allow CH oxidation reactions to be more readily incorporated into synthetic planning.

Timothy Newhouse, 

Prof. Dr. Phil S. Baran, Angew. Chem. Int. Ed. 2011

DOI: 10.1002/anie.201006368

Luminescent micro and nanogel formation from AB3 type poly(aryl ether) dendron derivatives without conventional multi-interactive gelation motifs - New Journal of Chemistry (RSC Publishing)

We report the synthesis, gelation and photophysical properties of luminescent AB₃ type poly(aryl ether) dendron derivatives in the absence of conventional multi-interactive gelation motifs. The gelation process is controlled through employing partial polar solvent milieu, which significantly enhances the propensity of π–π interaction between the aryl units present in the system. The self-assembly leads to unprecedented gelation through entrapping solvent molecules in the fibrillar arrangement of poly(aryl ether) units. The strategy was further utilized to prepare an excimer based photoluminescent gel through incorporating anthracene units in the dendrons. The close proximity between the anthracene units in the gel renders the formation of anthracene excimers at room temperature, resulting in the emission of bright green light from the gel, upon UV excitation. The study suggests that the size and packing of the self-assembled fibre can be controlled by the generation and functional groups present in the dendron. Furthermore, the strategy envisages an easy approach to generate fluorescent Low Molecular-mass Organic Gelator (LMOG) through incorporating poly cyclic aromatic hydrocarbon units to the poly(aryl ether) dendrons, since the self-assembly is largely guided by π–π interactions.

DOI: 10.1039/C1NJ20136K

Breaking the regioselectivity rule for acrylate insertion in the Mizoroki–Heck reaction

Abstract

In modern methods for the preparation of small molecules and polymers, the insertion of substrate carbon–carbon double bonds into metal–carbon bonds is a fundamental step of paramount importance. This issue is illustrated by Mizoroki–Heck coupling as the most prominent example in organic synthesis and also by catalytic insertion polymerization. For unsymmetric substrates H₂C = CHX the regioselectivity of insertion is decisive for the nature of the product formed. Electron-deficient olefins insert selectively in a 2,1-fashion for electronic reasons. A means for controlling this regioselectivity is lacking to date. In a combined experimental and theoretical study, we now report that, by destabilizing the transition state of 2,1-insertion via steric interactions, the regioselectivity of methyl acrylate insertion into palladium–methyl and phenyl bonds can be inverted entirely to yield the opposite “regioirregular” products in stoichiometric reactions. Insights from these experiments will aid the rational design of complexes which enable a catalytic and regioirregular Mizoroki–Heck reaction of electron-deficient olefins.

PNAS: doi:10.1073/pnas.1101497108

Cross-Coupling Reactions Of Organoboranes: An Easy Way To Construct C[BOND]C Bonds (Nobel Lecture) - Suzuki - 2011 - Angewandte Chemie International Edition - Wiley Online Library

Cross-Coupling Reactions Of Organoboranes: An Easy Way To Construct C[BOND]C Bonds (Nobel Lecture) :

Tools for chemists: The Nobel Prize in Chemie 2010 was awarded for research on palladium-catalyzed cross-coupling in organic synthesis. Two of the Laureates, A. Suzuki and E. Negishi, report here first hand on the historical development and the current status of this research.

DOI: 10.1002/anie.201101379

Metal-Free Direct Arylations of Indoles and Pyrroles with Diaryliodonium Salts

Direct arylations of indoles and pyrroles with differently substituted diaryliodonium salts were shown to efficiently proceed in the absence of metal catalysts.

DOI: 10.1021/ol200601e