Abstract We report a simple protocol for the photochemical Giese addition of C(sp 3 )‐centered radicals to variety electron‐poor olefins. The chemistry does not require external photoredox catalysts. Instead, it harnesses excited‐state reactivity 4‐alkyl‐1,4‐dihydropyridines (4‐alkyl‐DHPs) generate alkyl radicals. Crucial is use catalytic amount Ni(bpy) 2+ (bpy=2,2′‐bipyridyl), which acts as an electron mediator facilitate redox processes involving fleeting and highly reactive intermediates.

We report herein a visible light-mediated C-H hydroxyalkylation of quinolines and isoquinolines that proceeds via radical path. The process exploits the excited-state reactivity 4-acyl-1,4-dihydropyridines, which can readily generate acyl radicals upon blue light absorption. By avoiding need for external oxidants, this radical-generating strategy enables departure from classical, oxidative Minisci-type pattern unlocks unique reactivity, leading to hydroxyalkylated heteroarenes. Mechanistic...

The mechanism of boron-to-nickel transmetalation, the key step nickel-catalyzed Suzuki-Miyaura (S-M) coupling, was examined both experimentally and theoretically. Dinuclear μ-hydroxo-bridged complexes formed by reaction trans-[ArNi(PR3)2X] with hydroxide are not directly involved in but they rather act as a resting state for catalyst. base/boronic acid ratio is crucial parameter, it modulates extent formation these dinuclear species thus tunes catalytic activity. These findings explain some...

The oxidative addition (OA) of organic electrophiles to Pd(0) is a fundamental step in organopalladium chemistry and plays key role palladium-catalyzed cross-coupling reactions. This perspective summarizes selected mechanistic studies the Pd(0)-to-Pd(II) OA process involving halides pseudohalides with focus on systems relevant catalytic results are organized according nature supporting ligands, extracting general trends, describing most examples. formation active species from precatalysts...

This review with 387 references covers the literature until end of November 2013 on synthesis multiply arylated heteroarenes via highly selective palladium-catalyzed direct C–H arylation reactions heteroarene derivatives aryl halides or pseudohalides aryliodonium salts. Particular attention has been made to describe biologically active compounds and substances that are privileged structural motifs in organic materials. The practicality, versatility, limitations various developed protocols...

Experimental and theoretical mechanistic studies on the Cu(OTf)2-catalyzed hydroamination reaction of terminal allenes with secondary amines reveal that in situ generated cationic Cu(I) is catalytically active species explain observed regio- stereoselectivity for unbranched E product. Insight into structure relevant transition states allowed generalization this methodology to allenamides N-allenylcarbamates under unprecedentedly mild functional-group-tolerant conditions. Chelation effects by...

Understanding the nature of intermediate species operating within a palladium catalytic cycle is crucial for developing efficient cross-coupling reactions. Even though XPhos/Pd(OAc)2 system has found numerous applications, active remains elusive. A Pd0 complex ligated to XPhos been detected and characterized in situ first time using cyclic voltammetry NMR techniques. In presence XPhos, Pd(OAc)2 initially associates with ligand form solution, which as PdII (OAc)2 (XPhos). This center then...

Abstract Aryl azole scaffolds are present in a wide range of pharmaceutically relevant molecules. Their ortho-selective metalation at the aryl ring is challenging, due to competitive more acidic heterocycle. Seeking practical access key Active Pharmaceutical Ingredient (API) intermediate currently development, we investigated 1-aryl-1 H -1,2,3-triazoles and other related heterocycles with sterically hindered metal-amide bases. We report here room temperature highly regioselective...

This review with 800 references illustrates applications of Suzuki-Miyaura (S.-M.) reactions in the total syntheses 147 natural products that were made period 2010–2013. The has been organized on basis seven classes phosphane-based Pd catalysts have used reported syntheses. Emphasis given to describe and discuss experimental conditions Pd-catalyzed cross-coupling also outlining methods prepare reactants. A focus set biological pharmacological properties as well most significant steps...

Abstract Allenes are commonly used in metal‐mediated transformations, cycloaddition reactions, and radical processes. However, their activation by single‐electron transfer (SET) is largely underexplored. Herein, we report a visible light‐driven enantioselective organocatalytic process that uses the excited‐state reactivity of chiral iminium ions to activate allenes SET oxidation. The ensuing allene cation radicals participate stereocontrolled cascade reactions deliver bicyclic scaffolds with...

Abstract We report a simple protocol for the photochemical Giese addition of C(sp 3 )‐centered radicals to variety electron‐poor olefins. The chemistry does not require external photoredox catalysts. Instead, it harnesses excited‐state reactivity 4‐alkyl‐1,4‐dihydropyridines (4‐alkyl‐DHPs) generate alkyl radicals. Crucial is use catalytic amount Ni(bpy) 2+ (bpy=2,2′‐bipyridyl), which acts as an electron mediator facilitate redox processes involving fleeting and highly reactive intermediates.

Abstract An in‐depth mechanistic study on the palladium‐catalyzed direct arylation of imidazoles at C‐5 position is presented. The interactions triphenylphosphine (PPh 3 )‐ligated aryl‐Pd species with 1,2‐dimethyl‐1 H ‐imidazole (dmim) have been studied in detail. In contrast previous suggestions, phosphine‐ligated organo‐Pd are not active and reaction proceeds through imidazole‐ligated intermediates. kinetics oxidative addition aryl halides dmim‐ligated Pd(0) characterized a Pd(dba) 2 /dmim...

While 31P NMR is a major technique to characterize phosphine-ligated transition-metal complexes—which are ubiquitous in catalysis—31P chemical shifts difficult predict using empirical rules or tabulated data. Aiming at filling this gap, we propose here guidelines enabling their prediction modest computational cost. Rooted density functional theory, our protocol features structural optimization and magnetic shielding tensor calculations performed global hybrid level tailored locally dense...

Kinetic, spectroscopic and computational studies examining a palladium-catalyzed imidoylative coupling highlight the dual role of isocyanides as both substrates ligands for this class transformations. The synthesis secondary amides from aryl halides water is presented case study. kinetics oxidative addition ArI with RNC-ligated Pd0 species have been studied resulting imidoyl complex [(ArC=NR)Pd(CNR)2 I] (Ar=4-F-C6 H4 , R=tBu) has isolated characterized by X-ray diffraction. unprecedented...

Abstract Building on mechanistic studies, the innate capability of azoles to act as a directing group has been exploited design an efficient and simple procedure for hydroamination N ‐allenylazoles with secondary amines. The reaction proceeds under mild conditions by copper(I) catalysis yielding corresponding original linear E allylic amines total regio‐ stereoselectivity. Density Functional Theory (DFT) calculations offer explanation significantly higher reactivity ‐allenyl‐(1,2)‐azoles...

Abstract We report herein a visible light‐mediated C−H hydroxyalkylation of quinolines and isoquinolines that proceeds via radical path. The process exploits the excited‐state reactivity 4‐acyl‐1,4‐dihydropyridines, which can readily generate acyl radicals upon blue light absorption. By avoiding need for external oxidants, this radical‐generating strategy enables departure from classical, oxidative Minisci‐type pattern unlocks unique reactivity, leading to hydroxyalkylated heteroarenes....

Diphosphine ligands are frequently used in palladium-catalyzed Suzuki–Miyaura (S-M) reactions. Despite their widespread application both academic and industrial settings, role the B-to-Pd transmetalation has not been firmly established. We combined electrochemistry, NMR spectroscopy, DFT calculations to elucidate of dppf (1,1′-bis(diphenylphosphino)ferrocene) this key elementary step S-M reaction. observed that excess inhibits involving PhB(OH)2 dppf-ligated arylpalladium(II) complexes,...

A series of 1,4-phenylene-spaced bis-imidazoles with fluorescence quantum yields up to 0.90 and large Stokes shifts have been designed synthesized using recently developed regioselective direct CH arylation protocols. All the fluorophores show a bright blue-green emission that is well retained in solid state. DFT calculations attributed their excellent luminescence properties significant planarization molecules equilibrium structures excited electronic states.

Abstract Among all the chemical and biotechnological strategies implemented to extract energy from oxygenic photosynthesis, several concern use of intact photosynthetic organisms (algae, cyanobacteria…). This means rerouting (fully or partially) electron flow chain an outer collecting electrode thus generating a photocurrent. While diverting electrons living biological systems is encouraging approach, this strategy limited by need shuttle. Redox mediators that are able interact with embedded...

Abstract Oxidative addition of iodoarenes (ArI) to Pd 0 ligated by 1‐methyl‐1 H ‐imidazole (mim) in polar solvents leads cationic arylpalladium(II) complexes [ArPd(mim) 3 ] + . Kinetic analyses evidence that this reaction is second order with respect the concentration , and a mechanism involving cooperative intervention two centers has been postulated explain finding. This unusual behavior also observed other nitrogen‐containing ligands it general for iodobenzenes substituted...

A copper-catalysed hydroamination reaction of N-allenylsulfonamides with amines has been developed through a rational approach based on mechanistic studies. The is promoted by simple copper(I) catalyst and proceeds at room temperature complete regioselectivity excellent stereoselectivity towards linear (E)-N-(3-aminoprop-1-enyl)sulfonamides. Density Functional Theory (DFT) studies allow interpreting the key role unsaturated substituents nitrogen as ancillary coordinating moieties for copper catalyst.

Abstract Benzofurans can undergo ring‐opening by a palladium‐catalyzed process resulting in C−O bond breaking. Benzofuran‐tethered 2‐iodoanilines give synthetically interesting 2‐(3‐indolylmethyl)phenols an overall reductive process. Mechanistic studies suggest that this unusual reaction proceeds carbopalladation of benzofuran giving 3‐palladated 2,3‐dihydrobenzofuran intermediate, which then fragments uncommon trans ‐elimination the phenoxide group β to metal. In transformation, N ,...

The mechanism of the copper-catalyzed arylation nitrogen heterocycles using anilines via diazonium salts has been studied by combining DFT and experimental data. A CuI/CuIII redox is proposed. Our study revealed multiple roles acid/base couple AcOH/AcO–. An in situ formed triazene species maintains a low concentration reaction medium, which ensures limited formation decomposition products. results calculations have explained lower reactivity imidazole nucleophiles as compared with pyrazole reaction.

Abstract Review: [228 refs.