Functionalized Aryl Iodides Research Articles

Glycerol as Reaction Medium for Sonogashira Couplings: A Green Approach for the Synthesis of New Triarylamine-Based Materials with Potential Application in Optoelectronics.

This study focuses on the design, eco-friendly synthesis, and characterization of several novel three-legged triphenylamine derivatives. By performing Sonogashira couplings of functionalized aryl iodides with tris(4-ethynylphenyl)amine in glycerol, a readily available bio-derived solvent, we achieved the synthesis of target products in short times and high yields, up to 94 %, with consistently lower E-factors and reduced costs compared to standard conditions using toluene as the reaction medium. The target molecules possess a D-(π-A)₃ or D-(π-D)₃ structure, where an electron-donating core connects to three electron-donating (D) or electron-accepting (A) peripheral aromatic subunits through an acetylene spacer. Their main optical and electronic properties have been determined experimentally and by DFT simulations and suggest a possible implementation in energy conversion technologies such as luminescent solar concentrators (LSCs) and perovskite solar cells (PSCs).

Alkyl Tosylates as Alkylating Reagents in the Catellani Reaction

A cooperative catalytic system involving a Pd/XPhos complex and inexpensive 5-norbornene-2-carbonitrile that enables the use of alkyl tosylates as alkylating reagents in the Catellani reaction has been developed. This mild, scalable protocol is compatible with a range of readily available functionalized aryl iodides and alkyl tosylates, as well as terminating olefins (45 examples, up to 97% yield).

Synthesis of Benzofused Dioxabicycle Scaffolds via a Catellani Strategy.

Reported is a modular strategy for the preparation of the unique benzofused dioxabicycle scaffolds involving a Catellani reaction of aryl iodides, epoxides, and terminal alkynes and an oxa-cyclization. This is a mild, scalable, chemoselective, and atom-economical protocol, compatible with various functionalized aryl iodides, epoxides, and terminal alkynes. With the ability to build up the molecular complexity rapidly and efficiently from feedstock chemicals, this method will have wide applications in organic synthesis.

Direct Arylations via C–H Bond Functionalization of 1,2,3‐Triazoles by a Reusable Pd/C Catalyst Under Solvent‐Free Conditions

Fully substituted triazoles are synthesized by a sustainable direct arylation reaction performed under solvent‐free conditions and in the presence of a recyclable Pd/C heterogeneous catalyst. Exclusion of air as well as anhydrous conditions are not required, enabling a convenient synthesis of 1,4,5‐trisubstituted 1,2,3‐triazoles and 1,2,3‐triazole‐fused isoindolines starting from 1,4‐disubstituted 1,2,3‐triazoles, easily prepared via click chemistry, and functionalized aryl iodides.

New Insights into the Reaction Capabilities of Ionic Organic Bases in Cu‐Catalyzed Amination

The application of ionic organic bases in the copper‐catalyzed amination reaction (Ullmann reaction) has been studied at room temperature, with sub‐mol‐% catalyst loadings, and with more challenging amines at elevated temperatures. The cation present in the base has been shown to have little effect on the reaction at standard catalyst and ancillary ligand loadings, whereas the choice of anion is crucial for good reactivity. A substrate scope carried out at room temperature with the best performing bases, TBAM and TBPM, showed both bases to be highly effective under these mild reaction conditions. Moreover, under sub‐mol % catalyst loadings and room temperature conditions, TBPM gave good to excellent yields for a number of different amines and functionalized aryl iodides (14 examples). However, reactions involving more challenging amines gave little or no yield. By using more forceful conditions (120 °C) moderate to excellent yields of cross‐coupled products containing more challenging amines was achievable using TBPM and to a lesser extent with TBAM. As part of this work a study on the stability of the organic bases at 120 °C was undertaken. TBAM is shown to decompose to give nBu3N and mono‐butylmalonate at higher temperatures, and this can be correlated to a decrease in performance in the coupling reaction. The phosphonium cations in TBPM did not undergo analogous reactivity but were shown instead to experience some degree of deprotonation at the α‐CH2 to generate phosphonium ylides. This however did not lead to a significantly degradation in the activity of the TBPM in the cross‐coupling reaction.

Palladium-Catalyzed Ortho-Silylation of Aryl Iodides with Concomitant Arylsilylation of Oxanorbornadiene: Accessing Functionalized (Z)-β-Substituted Vinylsilanes and Their Analogues

A palladium-catalyzed ortho-silylation of aryl iodides/arylsilylation of oxanorbornadiene/retro-Diels-Alder domino reaction was developed. Such a transformation provides access to various functionalized ( Z)-β-substituted vinylsilanes with exclusive selectivity using hexamethyldisilane as a bis-silylation reagent and 2,3-dicarbomethoxy-7-oxanorbornadiene (ONBD) as an ortho-C-H activator and ethylene surrogate. A variety of ( Z)-β-substituted vinylgermanes and ( Z)-β-substituted vinylstannanes were also obtained under mild reaction conditions. This atom-economical, stereoselective, and scalable approach is compatible with a diverse range of readily available functionalized aryl iodides.

Solvent-Free Pd-Catalyzed Heteroaryl-Aryl Coupling via C-H Bond Activation for the Synthesis of Extended Heteroaromatic Conjugated Molecules.

Direct arylation of thienopyrrolodione, diketopyrrolopyrroles, benzodithiophene derivatives, and fluorinated heteroarenes with functionalized aryl iodides is proven in solvent-free and non-anhydrous conditions. The reaction is performed in the presence of air and tolerates several functional groups on both the coupling partners, enabling a convenient synthesis of extended heteroaromatic conjugated molecules.

Epoxides as Alkylating Reagents for the Catellani Reaction

AbstractWe report a cooperative catalytic system comprising a PdII complex, XPhos, and the potassium salt of 5‐norbornene‐2‐carboxylic acid that enables the use of epoxides as alkylating reagents in the Catellani reaction, thereby expanding the existing paradigm of this powerful transformation. The potassium salt of inexpensive 5‐norbornene‐2‐carboxylic acid acts as both mediator and base in the process. This mild, chemoselective, scalable, and atom‐economical protocol is compatible with a wide variety of readily available functionalized aryl iodides and epoxides, as well as terminating olefins. The resulting products undergo facile oxa‐Michael addition to furnish ubiquitous isochroman scaffolds.

Epoxides as Alkylating Reagents for the Catellani Reaction.

We report a cooperative catalytic system comprising a PdII complex, XPhos, and the potassium salt of 5-norbornene-2-carboxylic acid that enables the use of epoxides as alkylating reagents in the Catellani reaction, thereby expanding the existing paradigm of this powerful transformation. The potassium salt of inexpensive 5-norbornene-2-carboxylic acid acts as both mediator and base in the process. This mild, chemoselective, scalable, and atom-economical protocol is compatible with a wide variety of readily available functionalized aryl iodides and epoxides, as well as terminating olefins. The resulting products undergo facile oxa-Michael addition to furnish ubiquitous isochroman scaffolds.

Pd/C-Catalyzed Aminocarbonylation of Aryl Iodides with Anthranils in Water Using Mo(CO)6 as the CO Source.

A convenient procedure for the synthesis of N-(2-carbonylaryl)benzamides has been developed. Through Pd/C-catalyzed aminocarbonylation of anthranils with various hindered and functionalized aryl iodides, the desired amides were afforded in moderate to good yields. The protocol is advantageous due to the recyclable Pd/C catalyst, safe Mo(CO)6 as the solid CO source, and environmentally benign water as solvent. No inert atmosphere protection is needed.

Pd-Catalyzed Thiophene-Aryl Coupling Reaction via C-H Bond Activation in Deep Eutectic Solvents.

Direct arylation of 5-octylthieno[3,4-c]pyrrole-4,6-dione with a series of functionalized aryl iodides via C-H bond activation is demonstrated in a deep eutectic solvent made of choline chloride and urea in non-anhydrous conditions and without exclusion of air. This is the first demonstration of a thiophene-aryl coupling via direct arylation in deep eutectic solvents.

Stereoselective Peptide Modifications via β-C(sp3)-H Arylations.

Palladium-catalyzed stereoselective β-arylations of phenylalanine, proline- and pipecolinic acid-containing peptides are a versatile tool for peptide modifications. The reactions proceed without epimerization of stereogenic centers in the peptide chain. If suitable functionalized aryl iodides are introduced, subsequent cross coupling reactions can be used for further modifications. The 8-amino quinoline (AQ) directing group can easily be removed, allowing the prolongation of the peptide chain at the C-terminus.

ChemInform Abstract: Palladium‐Catalyzed Difluoromethylthiolation of Heteroaryl Bromides, Iodides, Triflates and Aryl Iodides.

AbstractThe reaction has a broad substrate scope, thus tolerating a diverse range of heteroaryl halides and triflates as well as variously functionalized aryl iodides.

An efficient and recyclable thermoregulated phosphine–palladium catalyst for the carbonylative Suzuki coupling of aryl halides with arylboronic acids in water

An efficient protocol has been developed for the carbonylative Suzuki coupling of aryl halides using the thermoregulated phosphine–palladium as a reusable catalyst in pure water. This protocol was applied to a wide variety of hindered and functionalized aryl iodides and bromides with arylboronic acids, to afford the desired biaryl ketones in good to high yields. The palladium catalyst was easily recovered in the aqueous phase and reused up to eight cycles without a significant decrease in its activity.

Photo-induced Metal-Catalyst-Free Aromatic Finkelstein Reaction.

The facile iodination of aromatic compounds under mild conditions is a great challenge for both organic and medicinal chemistry. Particularly, the synthesis of functionalized aryl iodides by light has long been considered impossible due to their photo-lability, which actually makes aryl iodides popular starting materials in many photo-substitution reactions. Herein, a photo-induced halogen exchange in aryl or vinyl halides has been discovered for the first time. A broad scope of aryl iodides can be prepared in high yields at room temperature under exceptionally mild conditions without any metal or photo-redox catalysts. The presence of a catalytic amount of elemental iodine could promote the reaction significantly.

ChemInform Abstract: Copper‐Mediated Fluorination of Aryl Iodides.

AbstractThe fluorination of a diversity of functionalized aryl iodides is readily achieved by silver fluoride in the presence of a cationic copper complex.The reaction is proposed to proceed by C—F reductive elimination from an in situ generated aryl copper(III) fluoride.

Pd(OAc)2-Catalyzed Carbonylative Coupling of Aryl Iodide with Ortho-Haloamines in Water

The carbonylative cross coupling of aryl iodide with ortho-haloaniline to ortho-haloanilide using phosphine-free Pd(OAc)2 catalyst in water as a reaction medium has been studied. The present protocol facilitated the reaction of o-haloanilines with a wide variety of hindered and functionalized aryl iodides, affording good yields of the desired products. The protocol was also extended for the synthesis of benzoxazoles through cyclization of ortho-haloanilide using Cu(acac)2 catalyst.

Highly Convenient, Clean, Fast, and Reliable Sonogashira Coupling Reactions Promoted by Aminophosphine‐Based Pincer Complexes of Palladium Performed under Additive‐ and Amine‐Free Reaction Conditions

Abstractmagnified imageSequential addition of 1,1′,1′′‐phosphinetriyltripiperidine and 1,3‐diaminobenzene or resorcinol to toluene solutions of (cyclooctadiene)palladium dichloride [Pd(cod)(Cl)2] under nitrogen in “one pot” almost quantitatively yielded the aminophosphine‐based pincer complexes {[C6H3‐2,6‐(XP{piperidinyl}2)2]Pd(Cl)} (X=NH 1; X=O 2). Complex 1 (and to a minor extent 2) proved to be efficient Sonogashira catalysts, which allow the quantitative coupling of various electronically deactivated and/or sterically hindered and functionalized aryl iodides and aryl bromides with several alkynes as coupling partners within very short reaction times and low catalyst loadings. Importantly, in contrast to most of the Sonogashira catalysts, which either are both air‐ and moisture‐sensitive and/or require the addition of co‐catalysts, such as copper(I) iodide [CuI], for example, or a large excess of an amine, the coupling reactions were carried out without the use of amines, co‐catalysts or other aditives and without exclusion of air and moisture. Moreover, the desired products were exclusively formed (no side‐products were detected) without employing an excess of one of the substrates. Ethylene glycol and potassium phosphate (K3PO4) were found to be the ideal solvent and base for this transformation. Experimental observations strongly indicate that palladium nanoparticles are not the catalytically active form of 1 and 2. On the other hand, their transformation into another homogeneous catalytically active species cannot be excluded.

Preparation of Aryl and Heteroaryl Indium(III) Reagents by the Direct Insertion of Indium in the Presence of LiCl

Sensitive functional groups, including ketone, aldehyde, and ester groups, may be present in aryl indium reagents prepared in good to excellent yields by the treatment of aryl and heteroaryl iodides with indium powder in the presence of LiCl (see example). These functionalized organoindium(III) reagents readily undergo Pd-catalyzed cross-coupling with functionalized aryl iodides, including those containing NH or OH groups.

Copper-catalyzed arylation of phenylurea using KF/Al 2O 3

A mild and efficient method for the copper-catalyzed arylation of phenylurea is described. The coupling reaction of phenylurea with different functionalized aryl iodides in the presence of air stable CuI, N, N′-dibenzylethylenediamine as a ligand, and KF/Al 2O 3 as a base gives symmetrical and unsymmetrical diarylureas in relatively high yields.