Raji Chem World

Crucial role of copper in detection of metal-coordinating odorants

2012-02-29T07:45:00.000+05:30

PNAS, 2012, doi: 10.1073/pnas.1111297109

Synthesis of Olefin-Oxazoline Ligands (OlefOx) by Rhodium(III)-Catalyzed Oxidative Olefination

2012-02-28T14:32:00.000+05:30

ASC, 2012, DOI: 10.1002/adsc.201100711

Iron-Catalyzed Nitrogen-Directed Coupling of Arene and Aryl Bromides Mediated by Metallic Magnesium

2012-02-28T14:31:00.000+05:30

ASC, 2012, DOI: 10.1002/adsc.201100791

Rh-catalyzed intramolecular sp2 C–H bond difluoromethylenation

2012-02-28T00:48:00.000+05:30

Chem. Commun., 2012, 48, 3136-3138

Practical synthesis of aromatic nitriles via gallium-catalysed electrophilic cyanation of aromatic C–H bonds

2012-02-28T00:47:00.000+05:30

Chem. Commun., 2012, 48, 3127-3129

Aza-oxindole synthesis by oxidative coupling of Csp2–H and Csp3–H centers

2012-02-28T00:45:00.000+05:30

Chem. Commun., 2012, 48, 3064-3066

Palladium-Catalyzed Direct Hydroxymethylation of Aryl Halides and Triflates with Potassium Acetoxymethyltrifluoroborate

2012-02-24T00:38:00.000+05:30

Org. Lett., 2012, DOI: 10.1021/ol300149b

Synthesis of Densely Substituted α,β,γ,δ-Dienones via the PdII-Catalyzed Allylation, H-Migration, and Aerobic Oxidative δ-Hydride Elimination Cascade

2012-02-24T00:36:00.000+05:30

Org. Lett., 2012, DOI: 10.1021/ol203444g

Nickel-Catalyzed Intermolecular Insertion of Aryl Iodides to Nitriles: A Novel Method to Synthesize Arylketones

2012-02-24T00:34:00.000+05:30

Org. Lett., 2012, DOI: 10.1021/ol300153f

Nickel(0)-Catalyzed Heck Cross-Coupling via Activation of Aryl C–OPiv Bonds

2012-02-24T00:27:00.000+05:30

Org. Lett., 2012, DOI: 10.1021/ol203322v

Pd-Catalyzed Arylation/Oxidation of Benzylic C–H Bond

2012-02-24T00:25:00.000+05:30

Org. Lett., 2012, DOI: 10.1021/ol300037p

Intramolecular Pd(II)-Catalyzed Aerobic Oxidative Amination of Alkenes: Synthesis of Six-Membered N-Heterocycles

2012-02-24T00:14:00.000+05:30

Org. Lett., DOI: 10.1021/ol300030w

Synthesis of Pyridines from Ketoximes and Terminal Alkynes via C–H Bond Functionalization

2012-02-23T19:41:00.001+05:30

JOC, 2012, DOI: 10.1021/jo202280e

Synthesis of Benzisoxazolines by the Coupling of Arynes with Nitrones

2012-02-23T19:40:00.001+05:30

JOC, 2012, DOI: 10.1021/jo2025064

4-Aryl-2-quinolones from 3,3-Diarylacrylamides through Intramolecular Copper-Catalyzed C–H Functionalization/C–N Bond Formation

2012-02-23T19:39:00.000+05:30

JOC, 2012, DOI: 10.1021/jo202427m

Expedient Synthesis of Highly Substituted Pyrroles via Tandem Rearrangement of α-Diazo Oxime Ethers

2012-02-23T16:33:00.000+05:30

JACS, DOI: 10.1021/ja300552c

Highly Diastereoselective Synthesis of Tetrahydropyridines by a C–H Activation–Cyclization–Reduction Cascade - Journal of the American Chemical Society (ACS Publications)

2012-02-23T15:45:00.000+05:30

JACS, DOI: 10.1021/ja2119833

Fluorine Transfer to Alkyl Radicals

2012-02-23T15:42:00.000+05:30

JACS, DOI: 10.1021/ja211679v

Silver-Catalyzed Decarboxylative Chlorination of Aliphatic Carboxylic Acids

2012-02-23T15:41:00.000+05:30

JACS, DOI: 10.1021/ja210361z

Double 1,4-rhodium migration cascade in rhodium-catalysed arylative ring-opening/spirocyclisation of (3-arylcyclobutylidene)acetates

2012-02-23T14:41:00.000+05:30

Takanori Matsuda , Yuya Suda and Akira Takahashi

Chem. Commun., 2012, 48, 2988-2990

A facile route to flavone and neoflavone backbones via a regioselective palladium catalyzed oxidative Heck reaction

2012-02-23T14:38:00.000+05:30

Chem. Commun., 2012, 48, 2985-2987

Transition metal catalysis and nucleophilic fluorination

2012-02-23T14:34:00.000+05:30

Chem. Commun., 2012, 48, 2929-2942

Chemoselective synthesis of ketones and ketimines by addition of organometallic reagents to secondary amides : Nature Chemistry : Nature Publishing Group

2012-02-22T08:19:00.000+05:30

Nature Chemistry 4, 228–234 (2012)

Regioselective and Stereospecific Cross-Coupling of Primary Allylic Amines with Boronic Acids and Boronates through Palladium-Catalyzed C[BOND]N Bond Cleavage

2012-02-21T13:20:00.001+05:30

Cross Coupling of Acyl and Aminyl Radicals: Direct Synthesis of Amides Catalyzed by Bu4NI with TBHP as an Oxidant

2012-02-21T13:19:00.001+05:30

Anti-Markovnikov Hydration of Terminal Alkenes: A Coupled Catalytic Cycle Approach

2012-02-21T12:56:00.000+05:30

Use of dimethyl carbonate as a solvent greatly enhances the biaryl coupling of aryl iodides and organoboron reagents without adding any transition metal catalysts

2012-02-21T07:57:00.000+05:30

Chem. Commun., 2012, 48, 2912-2914

Mechanistic Studies on Direct Arylation of Pyridine N-Oxide: Evidence for Cooperative Catalysis between Two Distinct Palladium Centers

2012-02-19T04:53:00.000+05:30

DOI: 10.1021/ja2122156

Pd(II)/Brønsted Acid Catalyzed Enantioselective Allylic C–H Activation for the Synthesis of Spirocyclic Rings

2012-02-19T04:47:00.000+05:30

DOI: 10.1021/ja2102407

Palladium-catalysed cross-coupling of organosilicon reagents

2012-02-19T02:45:00.000+05:30

Chem. Soc. Rev., 2012, 41, 1845-1866

C[BOND]X (X=Br, I) Bond-Tolerant Aerobic Oxidative Cross- Coupling: A Strategy to Selectively Construct β-Aryl Ketones and Aldehydes

2012-02-18T21:26:00.000+05:30

DOI: 10.1002/adsc.201100782

One-pot β-alkylation of secondary alcohols with primary alcohols catalyzed by ruthenacycles

2012-02-18T21:24:00.000+05:30

Tetrahedron Letters

Volume 53, Issue 12, 21 March 2012, Pages 1450–1455

Diamidocarbenes as versatile and reversible [2 + 1] cycloaddition reagents

2012-02-18T21:01:00.000+05:30

Nature Chemistry (2012) doi:10.1038/nchem.1267

Efficient Iron-Catalyzed Direct β-Alkylation of Secondary Alcohols with Primary Alcohols

2012-02-14T15:56:00.002+05:30

Copper-Catalyzed Domino Synthesis of Benzimidazo[2,1-b]quin- azolin-12(6H)-ones Using Cyanamide as a Building Block

2012-02-14T15:56:00.001+05:30

A general and selective copper-catalyzed reduction of secondary amides

2012-02-14T15:56:00.000+05:30

Ortho-Trifluoromethylation of Functionalized Aromatic Triazenes

2012-02-14T15:52:00.000+05:30

Iron-Catalyzed Synthesis of β-Chlorovinyl and α,β-Alkynyl Ketones from Terminal and Silylated Alkynes with Acid Chlorides - Gandeepan - 2012 - Advanced Synthesis & Catalysis - Wiley Online Library

2012-02-14T15:15:00.000+05:30

Abstract
A simple efficient method for the iron(III)-catalyzed synthesis of substituted β-chlorovinyl ketones and α,β-alkynyl ketones from terminal and silyl-substituted alkynes with acid chlorides, respectively, is described. This method features easily available starting materials, a cheap and non-toxic catalyst, simple manipulation and mild reaction conditions. Evidence shows that the catalytic addition of the acid chloride to a terminal alkyne to give (Z)-β-chlorovinyl ketones favours a concerted pathway via a four-membered ring transition state between the two alkyne carbons and the carbon-chloride bond of the acid chloride.

Parthasarathy Gandeepan,
Kanniyappan Parthasarathy,
Tsu-Hui Su,
Chien-Hong Cheng^*

DOI: 10.1002/adsc.201100670

An Alternative Approach to para-C–H Arylation of Phenol: Palladium-Catalyzed Tandem γ-Arylation/Aromatization of 2-Cyclohexen-1-one Derivatives - Organic Letters (ACS Publications)

2012-02-07T13:58:00.000+05:30

Palladium-Catalyzed Oxidative Heck Coupling Reaction for Direct Synthesis of 4-Arylcoumarins Using Coumarins and Arylboronic Acids

2012-02-07T13:38:00.001+05:30

Synthesis of δ-Bromo γ,δ-Unsaturated Carbonyl Compounds via Palladium-Catalyzed Bromoalkylation of Alkynoates

2012-02-07T13:37:00.001+05:30

Palladium-catalyzed regio- and stereoselective intermolecular tandem reaction of electron-deficient alkynes, CuBr2, and allylic alcohol to synthesize δ-bromo-γ,δ-unsaturated carbonyls was developed. A mechanism involving bromopalladation of alkyne, followed by insertion of allylic alcohol and allylic hydrogen shift, is proposed. The shift of allylic hydrogen is the rate-limiting step in this reaction.

Allenes in Molecular Materials - Rivera-Fuentes - 2012 - Angewandte Chemie International Edition - Wiley Online Library

2012-02-07T11:35:00.000+05:30

This Minireview provides a critical account of the development of allene-containing advanced functional materials, starting with the design and synthesis of stable and enantiopure building blocks. A variety of systems, including shape-persistent macrocycles, foldamers, polymers, charge-transfer chromophores, dendrimers, liquid crystals, and redox-switchable chiral chromophores are discussed from the viewpoint of their syntheses, properties, and potential applications. The goal of this Minireview is to inspire new uses of enantiopure allenes for the rational design of advanced materials.

Chiral Monodentate Phosphines and Bulky Carboxylic Acids: Cooperative Effects in Palladium-Catalyzed Enantioselective C(sp3)–H Functionalization

2012-02-07T11:34:00.000+05:30

Teaming up: The important indoline scaffold is provided with enantiomeric ratios of up to 98:2 in palladium(0)-catalyzed C(sp3)–H activations of aryl triflates. The key is the combination of the electron-rich monodentate Sagephos and the bulky 9H-xanthene-9-carboxylic acid. Both participate in a highly cooperative manner in the enantiodetermining concerted-deprotonation-metalation step (see scheme, Tf=triflate).

Palladium-Catalyzed Amidation by Chemoselective C(sp3)[BOND]H Activation: Concise Route to Oxindoles Using a Carbamoyl Chloride Precursor

2012-02-07T11:33:00.000+05:30

Quite select: A new strategy was developed for the synthesis of various oxindoles from carbamoyl chlorides. Under the optimum reaction conditions, with Ad2PBu as a ligand, tBuCONHOH as an additive, and a CO atmosphere, selective C(sp3)H activation proceeded in the presence of a C(sp2)H bond. Ad=adamantyl.

Extrusion of CO from Aryl Ketones: Rhodium(I)-Catalyzed C[BOND]C Bond Cleavage Directed by a Pyridine Group - Lei - 2012 - Angewandte Chemie International Edition - Wiley Online Library

2012-02-07T11:30:00.001+05:30

Snipping tool: The rhodium(I)-catalyzed extrusion of carbon monoxide from biaryl ketones and alkyl/alkenyl aryl ketones was developed to produce biaryls and alkyl/alkenyl arenes, respectively, in high yields (see scheme). A wide range of functionalities are tolerated. Not only does this method provide an alternative pathway to construct useful scaffolds, but also offers a new strategy for C-C bond activation.

Palladium-Catalyzed Intermolecular C(sp3)[BOND]H Amidation

2012-02-07T11:29:00.000+05:30

Dual capacity: A new palladium-catalyzed intermolecular sequence consisting of the CH activation and amidation of methyl groups relies on N-fluorobis(phenylsulfonyl)imide (NFSI) as both the oxidant and the nitrogen source. The reaction provides the corresponding arylamines as bissulfonimides along with HF as the only by-product. Both experimental and computational results suggest the involvement of a monomeric palladium(IV) intermediate.

Copper-Catalyzed Cross-Coupling Interrupted by an Opportunistic Smiles Rearrangement: An Efficient Domino Approach to Dibenzoxazepinones

2012-02-07T11:27:00.000+05:30

Synthesis of 3-Fluoro-3-aryl Oxindoles: Direct Enantioselective α Arylation of Amides

2012-02-07T11:25:00.000+05:30

Modus operandi: Catalytic access to the title compounds through a new asymmetric α-arylation protocol is reported (see scheme). These products are formed in good yields and excellent enantioselectivities using a new and easily synthesized chiral N-heterocyclic carbene (NHC) ligand. Advanced DFT calculations reveal the properties of the NHC ligand and the mode of operation of the catalyst.

DOI: 10.1002/anie.201200206

Gold-Catalyzed Oxidative Cyclizations of cis-3-En-1-ynes to Form Cyclopentenone Derivatives - Bhunia - 2012 - Angewandte Chemie International Edition - Wiley Online Library

2012-02-07T11:23:00.000+05:30

Golden tendencies: The title reaction for synthesizing cyclopentenone derivatives utilizes a gold complex and 8-methylquinoline oxide as catalytic system (see scheme; IPr=1,3-bis(diisopropylphenyl)imidazol-2-ylidene). Such products are not attainable using diazocarbonyl reagents as the gold carbenoids tend towards reacting with C-H bonds.

DOI: 10.1002/anie.201108027

Amine Synthesis through Mild Catalytic Hydrosilylation of Imines using Polymethylhydroxysiloxane and [RuCl2(arene)]2 Catalysts

2012-02-07T11:13:00.000+05:30

DOI: 10.1002/cssc.201100585

Recent advances in transition-metal-free carbon–carbon and carbon–heteroatom bond-forming reactions using arynes

2012-02-03T17:26:00.001+05:30

Cobalt catalysts for the coupling of CO2 and epoxides to provide polycarbonates and cyclic carbonates

2012-02-03T16:23:00.000+05:30

This comprehensive tutorial review focuses on well-defined cobalt complexes that serve as homogeneous catalysts for the production of polycarbonates and cyclic carbonates from the coupling of carbon dioxide and epoxides. Special considerations are given to the mechanistic pathways involved in these processes.

Green chemistry oriented organic synthesis in water

2012-02-03T16:21:00.001+05:30

The use of water as solvent features many benefits such as improving reactivities and selectivities, simplifying the workup procedures, enabling the recycling of the catalyst and allowing mild reaction conditions and protecting-group free synthesis in addition to being benign itself. In addition, exploring organic chemistry in water can lead to uncommon reactivities and selectivities complementing the organic chemists' synthetic toolbox in organic solvents. Studying chemistry in water also allows insight to be gained into Nature's way of chemical synthesis. However, using water as solvent is not always green. This tutorial reviewbriefly discusses organic synthesis in water with a Green Chemistry perspective.

Oxidative Prins and Prins/Friedel–Crafts cyclizations for the stereoselective synthesis of dioxabicycles and hexahydro-1H-benzo[f]isochromenes via the benzylic C–H activation

2012-02-02T14:03:00.000+05:30

1-Benzyl ethers of (E)- and (Z)-hex-3-en-1,6-diols and hept-3-en-1,7-diols undergo a smooth oxidative cyclization with DDQ in the presence of In(OTf)₃ through a sequential C–H bond activation and an intramolecular Prins cyclization to afford the corresponding trans- and cis-fused hexahydro-2H-furo[3,2-c]pyrans and octahydropyrano[4,3-b]pyrans respectively in good yields with an excellent stereoselectivity. Aryl tethered homoallylbenzyl ethers such as benzyl ethers of (E)- and (Z)-6-arylhex-3-enyl alcohols undergo a tandem Prins/Friedel–Crafts cyclization in the presence of stoichiometric amounts of DDQ and SnCl₄via the benzylic C–H bond activation to furnish the corresponding trans- and cis-fused hexahydro-1H-benzo[f]isochromenes in good yields with complete stereoselectivity.

The Triple Role of Fluoride Ions in Palladium-Catalyzed Suzuki–Miyaura Reactions: Unprecedented Transmetalation from [ArPdFL2] Complexes

2012-02-02T13:46:00.000+05:30

Direct Titanium-Mediated Conversion of Ketones into Enamides with Ammonia and Acetic Anhydride

2012-02-02T13:45:00.001+05:30

Tuning the Regioselectivity of Palladium-Catalyzed Direct Arylation of Azoles by Metal Coordination

2012-01-31T11:46:00.000+05:30

Cationic Ruthenium(II) Catalysts for Oxidative C–H/N–H Bond Functionalizations of Anilines with Removable Directing Group: Synthesis of Indoles in Water

2012-01-31T11:39:00.000+05:30

Synthesis of Indolo [1,2-a]Quinoxalines via a Pd-Catalyzed Regioselective C–H Olefination/Cyclization Sequence

2012-01-31T11:37:00.001+05:30

Ruthenium-Catalyzed Oxidative C–H Bond Olefination of N-Methoxybenzamides Using an Oxidizing Directing Group

2012-01-31T11:34:00.001+05:30

Tandem Rh(III)-Catalyzed Oxidative Acylation of Secondary Benzamides with Aldehydes and Intramolecular Cyclization: The Direct Synthesis of 3-Hydroxyisoindolin-1-ones

2012-01-31T11:33:00.000+05:30

Ruthenium-Catalyzed Oxidative C–H Alkenylations of Anilides and Benzamides in Water

2012-01-31T11:28:00.001+05:30

Versatile Synthesis of Isocoumarins and α-Pyrones by Ruthenium-Catalyzed Oxidative C–H/O–H Bond Cleavages

2012-01-31T11:27:00.001+05:30

Iron-Catalyzed Regio- and Stereoselective Chlorosulfonylation of Terminal Alkynes with Aromatic Sulfonyl Chlorides

2012-01-31T11:24:00.000+05:30

Terminal alkynes react with aromatic sulfonyl chlorides in the presence of an iron(II) catalyst and a phosphine ligand to give (E)-β-chlorovinylsulfones with 100% regio- and stereoselectivity. Various functional groups, such as chloride, bromide, iodide, nitro, ketone, and aldehyde, are tolerated under the reaction conditions. Addition of tosyl chloride to a 1,6-enyne followed by radical 5-exo-trig cyclization gave an exocyclic alkenylsulfone.

Rhodium-Catalyzed Xanthone Formation from 2-Aryloxybenzaldehydes via Cross-Dehydrogenative Coupling (CDC)

2012-01-31T11:21:00.000+05:30

Cu-Catalyzed Oxidative C(sp2)–H Cycloetherification of o-Arylphenols for the Preparation of Dibenzofurans

2012-01-31T11:17:00.000+05:30

A new process involving copper-catalyzed aerobic C(sp2)–H activation, followed by cycloetherification, has been developed. This reaction serves as a direct method for the preparation of multisubstituted dibenzofurans starting with o-arylphenols. The presence of a strong para-electron-withdrawing group (e.g., NO2) on the phenol is essential for the success of the reaction.

Experimental and Computational Bridgehead C–H Bond Dissociation Enthalpies

2012-01-31T10:25:00.000+05:30

Computational Elucidation of the Internal Oxidant-Controlled Reaction Pathways in Rh(III)-Catalyzed Aromatic C–H Functionalization

2012-01-31T10:24:00.000+05:30

Palladium-Catalyzed Cascade Cyclization–Oxidative Olefination of tert-Butyl 2-Alkynylbenozates

2012-01-31T10:21:00.000+05:30

Copper-Catalyzed Oxidative Trifluoromethylation of Terminal Alkynes and Aryl Boronic Acids Using (Trifluoromethyl)trimethylsilane

2012-01-31T10:19:00.000+05:30

Overcoming the “Oxidant Problem”: Strategies to Use O2 as the Oxidant in Organometallic C–H Oxidation Reactions Catalyzed by Pd (and Cu)

2012-01-31T10:10:00.000+05:30

Oxidation reactions are key transformations in organic chemistry because they can increase chemical complexity and incorporate heteroatom substituents into carbon-based molecules. This principle is manifested in the conversion of petrochemical feedstocks into commodity chemicals and in the synthesis of fine chemicals, pharmaceuticals, and other complex organic molecules. The utility and function of these molecules correlate directly with the presence and specific placement of oxygen and nitrogen heteroatoms and other functional groups within the molecules.

Methods for selective oxidation of C–H bonds have expanded significantly over the past decade, and their role in the synthesis of organic chemicals will continue to increase. Our group’s contributions to this field are linked to our broader interest in the development and mechanistic understanding of aerobic oxidation reactions. Molecular oxygen (O2) is the ideal oxidant. Its low cost and lack of toxic byproducts make it a highly appealing reagent that can address key “green chemistry” priorities in industry. With strong economic and environmental incentives to use O2, the commmodity chemicals industry often uses aerobic oxidation reactions. In contrast, O2 is seldom used to prepare more-complex smaller-volume chemicals, a limitation that reflects, in part, the limited synthetic scope and utility of existing aerobic reactions.

Pd-catalyzed reactions represent some of the most versatile methods for selective C–H oxidation, but they often require stoichiometric transition-metal or organic oxidants, such as CuII, AgI, or benzoquinone. This Account describes recent strategies that we have identified to use O2 as the oxidant in these reactions. In Pd-catalyzed C–H oxidation reactions that form carbon-heteroatom bonds, the stoichiometric oxidant is often needed to promote difficult reductive elimination steps in the catalytic mechanism. To address this challenge, we have identified new ancillary ligands for Pd that promote reductive elimination, or replaced Pd with a Cu catalyst that undergoes facile reductive elimination from a CuIII intermediate. Both strategies have enabled O2 to be used as the sole stoichiometric oxidant in the catalytic reactions. C–H oxidation reactions that form the product via β-hydride or C–C reductive elimination steps tend to be more amenable to the use of O2. The use of new ancillary ligands has also overcome some of the limitations in these methods. Mechanistic studies are providing insights into some (but not yet all) of these advances in catalytic reactivity.

Iron-Catalyzed Intramolecular Allylic C–H Amination

2012-01-31T10:01:00.000+05:30

A highly selective C–H amination reaction under iron catalysis has been developed. This novel system, which employs an inexpensive, nontoxic [FeIIIPc] catalyst (typically used as an industrial ink additive), displays a strong preference for allylic C–H amination over aziridination and all other C–H bond types (i.e., allylic > benzylic > ethereal > 3° > 2° 1°). Moreover, in polyolefinic substrates, the site selectivity can be controlled by the electronic and steric character of the allylic C–H bond. Although this reaction is shown to proceed via a stepwise mechanism, the stereoretentive nature of C–H amination for 3° aliphatic C–H bonds suggests a very rapid radical rebound step.

Intermolecular Ritter-Type C–H Amination of Unactivated sp3 Carbons

2012-01-31T09:59:00.000+05:30

Intermolecular Ritter-type C–H amination of unactivated sp3 carbons has been developed. This new reaction proceeds under mild conditions using readily available reagents and an inexpensive source of nitrogen (acetonitrile). A broad scope of substrates can be aminated with this method since many functional groups are tolerated. This reaction also allows for the direct, innate C–H amination of a variety of hydrocarbons such as cyclohexane without the need of prefunctionalization or installation of a directing group.

Copper-Mediated Sequential Cyanation of Aryl C–B and Arene C–H Bonds Using Ammonium Iodide and DMF

2012-01-31T09:56:00.000+05:30

The cyanation of aromatic boronic acids, boronate esters, and borate salts was developed under copper-mediated oxidative conditions using ammonium iodide and DMF as the source of nitrogen and carbon atom of the cyano unit, respectively. The procedure was successfully extended to the cyanation of electron-rich benzenes, and regioselective introduction of a cyano group at the arene C–H bonds was also achieved. The observation that the reaction proceeds via a two-step process, initial iodination and then cyanation, led us to propose that ammonium iodide plays a dual role to provide iodide and nitrogen atom of the cyano moiety.

Zinc(II)-Catalyzed Redox Cross-Dehydrogenative Coupling of Propargylic Amines and Terminal Alkynes for Synthesis of N-Tethered 1,6-Enynes

2012-01-31T09:54:00.000+05:30

The zinc(II)-catalyzed redox cross-dehydrogenative coupling (CDC) of propargylic amines and terminal alkynes proceeds to afford N-tethered 1,6-enynes. In the current CDC reaction, a C(sp)–C(sp3) bond is formed between the carbon adjacent to the nitrogen atom in the propargylic amine and the terminal carbon of the alkyne with reduction of the C–C triple bond of the propargylic amine, which acts as an internal oxidant.

Mirror symmetry breaking and chiral amplification in foldamer-based supramolecular helical aggregates

2012-01-31T09:35:00.000+05:30

Spontaneous asymmetric generation of supramolecular chiral fibers was observed in the folding induced self-assembly of a lock-washer shaped foldamer. A secondary nucleation growth mechanism is proposed to explain the observed chiral amplification or deracemization of these supramolecular fibers.

[RhIIICp*]-Catalyzed Dehydrogenative Aryl[BOND]Aryl Bond Formation

2012-01-31T09:33:00.000+05:30

Fluorescent and Colorimetric Probes for Mercury(II): Tunable Structures of Electron Donor and π-Conjugated Bridge

2012-01-28T13:30:00.000+05:30

Copper(II)-Catalyzed Monoarylation of Vicinal Diols with Diaryliodonium Salts

2012-01-28T13:29:00.000+05:30

Oxidative Mizoroki–Heck-Type Reaction of Arylsulfonyl Hydrazides for a Highly Regio- and Stereoselective Synthesis of Polysubstituted Alkenes

2012-01-28T13:27:00.001+05:30

para-Selective Aerobic Oxidative C[BOND]H Olefination of Aminobenzenes Catalyzed by Palladium/Molybdovanadophosphoric acid/2,4,6-Trimethylbenzoic Acid System

2012-01-28T13:25:00.000+05:30

Transition-metal-free Coupling Reactions of Aryl Halides

2012-01-28T13:17:00.000+05:30

Transition metal catalysis plays a leading role in C(sp2)–C(sp2) bond formation through substitution reactions. On the other hand, a similar type of substitution reaction has recently been achieved without the aid of transition-metal catalysts. In this review, recent transition-metal-free coupling reactions of aryl halides with arenes, alkenes, or aryl Grignard reagents are summarized in view of SRN1 reaction.

Palladium-catalyzed allylic C–H amination of alkenes with N-fluorodibenzenesulfonimide: water plays an important role

2012-01-27T12:31:00.000+05:30

Up the Hill: Selective Double-Bond Isomerization of Terminal 1,3-Dienes towards Z-1,3-Dienes or 2Z,4E-Dienes

2012-01-25T14:23:00.000+05:30

Against all odds: Two different cobalt catalyst systems led to the selective isomerization of 1,3-dienes. In the case of the [CoBr2(py-imine)]-catalyzed reaction, the Z-1,3-diene was formed in a highly selective manner (see scheme). When the catalyst precursor [CoBr2(dpppMe2)] was applied, a double-bond migration and selective isomerization towards the 2Z,4E-configured 2,4-dienes were observed.

Aerobic Palladium(II)-Catalyzed 5-endo-trig Cyclization: An Entry into the Diastereoselective C-2 Alkenylation of Indoles with Tri- and Tetrasubstituted Double Bonds

2012-01-25T14:21:00.001+05:30

A Highly Efficient Gold-Catalyzed Oxidative C[BOND]C Coupling from C[BOND]H Bonds Using Air as Oxidant

2012-01-25T14:20:00.000+05:30

A breath of fresh air: The title reaction has been developed for the coupling of amines with nitroalkanes and different unmodified ketones using air as the sole oxidant under mild reaction conditions. The safe, convenient, and environmentally benign process, as well as the low catalyst loading, short reaction time, and good yields make this protocol very practical (see scheme).

Highly Regioselective Copper-Catalyzed Benzylic C[BOND]H Amination by N-Fluorobenzenesulfonimide

2012-01-25T14:18:00.000+05:30

Primary target: A practical and effective copper-catalyzed amination strategy for synthesizing various benzylic amines from benzylic hydrocarbons is described (see scheme; DCE=1,2-dichloroethane). Xylene substrates can undergo diamination reactions using this method. The remarkable preference for primary over secondary benzylic CH bonds has been observed for the first time.

Non-lattice surface oxygen species implicated in the catalytic partial oxidation of decane to oxygenated aromatics

2012-01-24T18:12:00.000+05:30

DNA nanotechnology: The world's smallest assembly line

2012-01-24T18:09:00.001+05:30

Palladium-Catalyzed Intermolecular Coupling of 2-Silylaryl Bromides with Alkynes: Synthesis of Benzosiloles and Heteroarene-Fused Siloles by Catalytic Cleavage of the C(sp3)[BOND]Si Bond

2012-01-24T17:04:00.001+05:30

Intramolecular Redox-Triggered C[BOND]H Functionalization

2012-01-24T17:03:00.000+05:30

Palladium-Catalyzed Carbonylative Dimerization of Styrenes to 1,5-Diarylpent-1-en-3-ones

2012-01-24T17:00:00.000+05:30

Palladium-Catalyzed Carbonylation of Amines: Switchable Approaches to Carbamates and N,N′-Disubstituted Ureas

2012-01-24T16:42:00.000+05:30

A Novel Sodium Nitrite-Catalyzed Oxidative Coupling for Constructing Polymethoxyphenanthrene Rings

2012-01-24T16:41:00.001+05:30

Palladium-Catalyzed Direct and Site-Selective Desulfitative Arylation of Indoles with Sodium Sulfinates

2012-01-24T16:41:00.000+05:30

Palladium-Catalyzed Oxidative C[BOND]C Bond Cleavage Cyclization of Biaryl-2-amines with Alkenes Involving C[BOND]H Olefination and Carboamination

2012-01-24T16:35:00.000+05:30

A new indole incorporated chemosensor exhibiting selective colorimetric and fluorescence ratiometric signaling of fluoride

2012-01-20T09:39:00.001+05:30

A method for the synthesis of 2-aminobenzoxazoles

2012-01-20T09:38:00.000+05:30

Abstract

A synthesis of 2-aminobenzoxazoles from the parent C–H compound is described. The procedure involves deprotonation at the 2-position of the benzoxazole and quenching the intermediate organolithium species with a halogen electrophile. The 2-halobenzoxazole is then treated in the same pot with an amine nucleophile to afford the desired product. The substrate scope and selectivity of the reaction are presented. The method is operationally simple and provides access to a variety of amine products bearing additional nucleophilic heteroatoms.

A Unique Class of Near-Infrared Functional Fluorescent Dyes with Carboxylic-Acid-Modulated Fluorescence ON/OFF Switching: Rational Design, Synthesis, Optical Properties, Theoretical Calculations, and Applications for Fluorescence Imaging in Living Animals

2012-01-20T09:33:00.000+05:30

Fluorescence imaging is one of the most powerful techniques for monitoring biomolecules in living systems. Fluorescent sensors with absorption and emission in the near-infrared (NIR) region are favorable for biological imaging applications in living animals, as NIR light leads to minimum photodamage, deep tissue penetration, and minimum background autofluorescence interference. Herein, we have introduced a new strategy to design NIR functional dyes with the carboxylic-acid-controlled fluorescence on–off switching mechanism by the spirocyclization. Based on the design strategy, we have developed a series of Changsha (CS1–6) NIR fluorophores, a unique new class of NIR functional fluorescent dyes, bearing excellent photophysical properties including large absorption extinction coefficients, high fluorescence quantum yields, high brightness, good photostability, and sufficient chemical stability. Significantly, the new CS1–6 NIR dyes are superior to the traditional rhodamine dyes with both absorption and emission in the NIR region while retaining the rhodamine-like fluorescence ON-OFF switching mechanism. In addition, we have performed quantum chemical calculations with the B3LYP exchange functional employing 6-31G* basis sets to shed light on the structure-optical properties of the new CS1–6 NIR dyes. Furthermore, using CS2 as a platform, we further constructed the novel NIR fluorescent TURN-ON sensor 7, which is capable of imaging endogenously produced HClO in the living animals, demonstrating the value of our new CS NIR functional fluorescent dyes. We expect that the design strategy may be extended for development of a wide variety of NIR functional dyes with a suitable fluorescence-controlled mechanism for many useful applications in biological studies.

Synthesis of a [2.2]paracyclophane based planar chiral palladacycle by a highly selective kinetic resolution/C–H activation reaction

2012-01-19T16:06:00.001+05:30