Palladium-catalyzed Coupling Reaction Research Articles

Nanoreactors Technology in Green Organic Synthesis

Background: Nanoreactors technology represents a promising tool for efficient and selective organic synthesis typically under “green” and sustainable reaction conditions. These structures with generating a confined reaction environment to accommodate that both reactants and catalysts can change the reaction pathways and induce new activities and selectivities. Objective: The paper reviews literature examples in which nanoreactors were employed in various types of organic and metal catalyzed reactions including multicomponent reactions, palladium-catalyzed coupling reactions, olefin metathesis, aza-Cope rearrangement, allylic alcohol isomerization, cyclization reactions, ring opening reactions, halogenation reactions, hydrolysis reactions, hydroformylation reactions, cascade reactions, addition reactions, oxidation reactions and reduction reactions. The reactions' survey is accompanied with the explanation of structure and performance of nanoreactors that are applied there. Conclusion: The availability of comprehensive information about the role of nanoreactors technology in green organic synthesis and investigation of different aspects of them such as their structures, mechanisms and synthetic utility can assist researchers in designing the greener approaches in organic synthesis.

Alcohol-soluble conjugated poly(fluorene-co-thiophene) as an electron-transport material for polymer light-emitting diodes

ABSTRACTA series of alternating polyfluorene copolymers containing fluorene (P1-OF), bithiophene (P2-BT), and thiophene (P3-TH) moieties have been synthesized via a palladium-catalyzed Suzuki coupling reaction. Among them, the P3-TH polymer highly contains hydroxyl groups which provides enough solubility in polar solvents such as alcohols and dimethylformamide. Multilayer polymer light-emitting diodes have been fabricated using a semiconducting polymer, F8BT, as an emissive layer and the methanol-soluble P3-TH as an electron-transport layer. By the device configuration of ITO/PEDOT/TFB/F8BT/P3-TH/LiF/Al, it shows a luminescence efficiency of 1.48 cd/A and a turn-on voltage of 4.6 V. The emission with maxima at 448 nm and 495 nm which fell in the blue region with the CIE coordinates (x = 0.18, y = 0.24).

Palladium-Catalyzed Asymmetric Three-Component Coupling Reaction

Palladium-Catalyzed Asymmetric Three-Component Coupling Reaction

Concise and Stereodivergent Synthesis of Carbasugars Reveals Unexpected Structure-Activity Relationship (SAR) of SGLT2 Inhibition

Carbasugar sodium-glucose cotransporter 2 (SGLT2) inhibitors are highly promising drug candidates for the treatment of Type 2 diabetes mellitus (T2DM). However, the clinical usage of carbasugar SGLT2 inhibitors has been underexplored, due to the lengthy synthetic routes and the lack of structure-activity relationship (SAR) studies of these compounds. Herein, we report a concise and stereodivergent synthetic route towards some novel carbasugar SGLT2 inhibitors, featuring an underexploited, regioselective, and stereospecific palladium-catalyzed allyl-aryl coupling reaction. This synthetic strategy, together with computational modeling, revealed the unexpected SAR of these carbasugar SGLT2 inhibitors, and enabled the discovery of a highly selective and potent SGLT2 inhibitor.

C1'-Azacycloalkyl Hexahydrocannabinols.

We report the design, synthesis, and biological evaluation of a novel class of cannabinergic ligands, namely C1'-azacycloalkyl hexahydrocannabinols. Our synthetic approaches utilize an advanced common chiral intermediate triflate from which all analogues could be derived. Key synthetic steps involve microwave-assisted Liebeskind-Srogl C-C cross-coupling and palladium-catalyzed decarboxylative coupling reactions. The C1'-N-methylazetidinyl and C1'-N-methylpyrrolidinyl analogues were found to be high affinity ligands for the CB1 and CB2 cannabinoid receptors.

Brønsted acid-mediated cascade cyclization of 2-propynolphenols/anilines leading to 4-halo-2H-chromenes and 1,2-dihydroquinolines

• Brønsted acid-mediated synthesis of 4-halo-2 H -chromenes and 1,2-dihydroquinolines. • The high yield, experimental simplicity and good functional-group applicability are the merits of this novel transformation. • This method can be enlarged to gram scale. A convenient strategy is present for easy construction of a series of 4-halo-2 H -chromenes and 1,2-dihydroquinolines through Brønsted acid-mediated cascade cyclization of readily accessible 2-propynolphenols/anilines. Our developed approaches prove have good functional-group applicabilities and could be enlarged to gram quantities in high yields. Moreover, the resulting halides could be further exploited in subsequent palladium-catalyzed coupling reactions.

Fluorescence Quenching of a Conjugated Polymer by Synergistic Amine-Carboxylic Acid and π-π Interactions for Selective Detection of Aromatic Amines in Aqueous Solution.

Fluorescence sensing of amine in aqueous solution is challenging. The various basicity and chemical structures of amines may lead to poor selectivity in aqueous solution, and selective fluorescence detection of primary aromatic amine is rarely reported. This paper presents design and synthesis of a fluorescent conjugated polymer for rapid and selective sensing of aromatic amines in aqueous solution. The fluorescent conjugated polymer, poly[fluorenyl-alt-p-phenyleneethynylene] with pendant carboxylic acid groups and long alky chains, is synthesized via palladium-catalyzed Sonogashira coupling reaction. The fluorescence of the polymer is selectively quenched by the aromatic amines in aqueous solution, whereas the aliphatic amines enhance the fluorescence of the polymer. The high selectivity to the aromatic amines, particularly to the environmentally important p-phenylenediamine, likely originates from the amplified π-π fluorescence quenching synergized by amine and carboxylic acid interaction. Our results demonstrate an effective material design strategy that may be extended to fluorescence sensing of other aromatic compounds.

β-CD/CuI catalyzed regioselective synthesis of iodo substituted 1,2,3-triazoles, imidazo[1,2-a]-pyridines and benzoimidazo[2,1-b]thiazoles in water and their functionalization

An environment benign process has been developed for the regioselective synthesis of 5-iodo-1,4-disubstituted-1,2,3-triazoles catalyzed by CuI/β-CD in water. Moreover, the process was manifested for the efficient synthesis of 2-iodo-imidazo[1,2-a]pyridines and 2-iodo-benzoimidazo[2,1-b]thiazoles in aqueous medium. Additionally, the iodinated derivatives were successfully modified via palladium catalyzed coupling reactions. The salient features of this methodology are in-situ formation of 1-iodoalkyne & alkyl/aryl azide under mild reaction conditions, high regio-selectivity and use of water as a greener solvent.

Palladium-Catalyzed sp2-sp3 Coupling of Chloromethylarenes with Allyltrimethoxysilane: Synthesis of Allyl Arenes.

Palladium-catalyzed remote sp2-sp3 coupling reaction of chloromethylarenes with allyltrimethoxysilane is described in this work. The allylation reaction regioselectively occurred on the para-positions of 1-(chloromethyl)naphthalenes and benzyl chlorides to form new C(sp2)-C(sp3) bonds. The reaction proceeds smoothly under mild conditions to produce allyl arenes in moderate to excellent yields.

Singlet-singlet energy transfer in carbazole-porphyrin dyads and triads

Donor-π-Acceptor (D-π-A) type carbazole-porphyrin dyads and triads were synthesized in good yields through palladium catalyzed coupling reactions. The length of the spacer between the D (carbazole) and A (porphyrin) was varied from “phenylethyne” to “ethyne linkage”. The effect of the linker length on the spectral properties of these D-π-A dyads and triads was studied. The N-butyl-3-ethynyl-carbazole was coupled with different porphyrins bearing either one or two meso-p-iodophenyl group/meso-bromo groups using palladium catalyst. All the dyads and triads were characterized by MALDI-MS, NMR, UV–vis absorption, fluorescence and cyclic voltammetry techniques. The S1 emission dynamics were analyzed by time-resolved spectroscopy (TCSPC); an efficient energy transfer up to 84% was observed from donor groups to the porphyrin core. Electrochemical studies revealed that, compounds having freebase porphyrin components are difficult to reduce as indicated by the cathodic shift in their reduction potentials. On the contrary, the compounds having zinc porphyrin components are easy to reduce as reflected by the anodic shift in their reduction potentials. The lowest HOMO-LUMO gap was found for the dyad which has short linker between D and A.

First direct catalytic difluoromethylations from ClCF2H

Researchers have traditionally prepared difluoromethylated compounds by the deoxyfluorination of aldehydes using harsh electrophilic fluorinating reactions. More recently, chemists have taken a milder approach by using preformed reagents to transfer a CF2H group to a target molecule. In this case, the preformed reagent is often made from fluoroalkyl halides such as chlorodifluoromethane, ClCF2H, an inexpensive industrial chemical used for making fluorinated polymers. Xingang Zhang and coworkers at Shanghai Institute of Organic Chemistry wondered if they couldn’t simplify difluoromethylations further by using ClCF2H directly in a catalytic process. The researchers have found that they indeed can carry out palladium-catalyzed coupling reactions between ClCF2H and aryl and heteroaryl boronic acids and esters to create an array of aromatic difluoromethyl derivatives, providing new opportunities to develop bioactive compounds used as pharmaceuticals, agrochemicals (one example shown), and flavors and fragrance...

Synthesis and electro-optical properties of spiro based host material for thermal stable blue phosphorescent OLED

ABSTRACTNew host material, namely 2,2′-bis(3,5-di(9H-carbazol-9-yl)phenyl)-9,9′-spirobi[fluorene] (spiro-mCP), was designed and synthesized by the palladium-catalyzed Suzuki coupling reaction between 9,9′-(5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1,3-phenylene)bis (9H-carbazole) and 2,2′-diiodo-9,9′-spirobi[fluorene]. Thermal, photophysical and electrochemical properties of spiro-mCP were investigated. Using spiro core leads to enhance thermal stability. Phosphorescent organic light-emitting diode constructed using a 7 wt% FIr6 doped spiro-mCP emitting layer produces bright blue emissions with a high luminescence efficiency of 5.8 cd/A.

Regioselective Three-Component Coupling by the Palladium-Catalyzed Reaction of 2-Fluoroallylic Acetates with Phenols and Imides

A palladium-catalyzed three-component coupling reaction of 2-fluoroallylic acetates with phenols, and imides is disclosed. The reaction was effectively catalyzed by [Pd(C₃H₅)Cl]₂/DPPF in the presence of Cs₂CO₃, and phenols and imides were introduced onto the allyl unit through the C–F bond activation. Furthermore, the reaction proceeds with both high regioselectivity and high <i>Z</i>-selectivity.

Synthesis and photoelectric properties of new Pr-bonded polymers by coordination of isopropyloxide and bipyridine unit

A series of novel praseodymium (Pr)-bonded polymers were successfully synthesized via the coordination reaction and palladium-catalyzed Suzuki coupling reaction of 2,7-dibromo-9,9′-dioctylfluorene and different amounts of 5,5′-dibromo-2,2′-bipyridine. The resulting polymers were characterized by 1H-NMR and GPC. The photoluminescence (PL) and electroluminescence (EL) properties of the resulting polymers were studied to explore the effects of the Pr triisopropyloxide. The results showed that the incorporation of Pr into the polymers caused better coplanarity and effective intermolecular or intramolecular interaction, leading to the higher emission intensity at long-wavelength. Further, it was also found that the emission light color could be tuned from blue to green by introduction of a small amount of Pr into the polymer main chain. A single-layer green emitting EL device based on PF(BipyPr)6 with 6 mol% Pr content was fabricated. The device had a low turn-on voltage of 6 V, a brightness of 705.3 cd·m−2, the maximum luminous efficiency of 1.53 cd·A−1 and the maximum power efficiency of 0.69 lm·W−1.

Palladium-Catalyzed Intramolecular Cross-Dehydrogenative Coupling: Synthesis of Fused Imidazo[1,2-a]pyrimidines and Pyrazolo[1,5-a]pyrimidines.

A palladium-catalyzed intramolecular dehydrogenative coupling reaction was developed for the synthesis of fused imidazo[1,2-a]pyrimidines and pyrazolo[1,5-a]pyrimidines. The developed protocol provides a practical approach for the synthesis of biologically important substituted pyrimidines from easily available substrates, with a broad substrate scope under mild reaction conditions.

Regioselective 1,2-addition of allenamides with N-haloimides: synthesis of 2-halo allylic aminal derivatives.

A strategy for the synthesis of 2-halo allylic aminal derivatives through regioselective 1,2-addition of allenamides with N-haloimides is presented. This reaction was conducted under very mild conditions and gave up to 99% yield. Moreover, the obtained halides allow functional group diversification by palladium-catalyzed coupling reactions, which could act as potential intermediates for the synthesis of valuable compounds.

Denitrogenative Suzuki and carbonylative Suzuki coupling reactions of benzotriazoles with boronic acids.

Unprecedented palladium-catalyzed denitrogenative Suzuki and carbonylative Suzuki coupling reactions of benzotriazoles with boronic acids have been realized, which afforded structurally diverse ortho-amino-substituted biaryl and biaryl ketone derivatives. The key to this success is due to the development of a rationally designed strategy to achieve the ring opening of benzotriazoles with a synergistic activating-stabilizing effect, which enables the in situ generation of the corresponding ortho-amino-arenediazonium species. The present work opens up a new avenue to utilize benzotriazoles as synthetic equivalents of ortho-amino-arenediazoniums, which otherwise could not be directly accessed by existing synthetic methods.

Alternating magnetic field mediated micro reaction system for palladium-catalyzed coupling reactions

A continuous flow reaction system in which a palladium magnetic catalyst was immobilized and vibrated by an alternating induced magnetic field was developed.

Palladium-catalyzed synthesis of indole fused coumarins via cross-dehydrogenative coupling

The present method describes a palladium-catalyzed cross-dehydrogenative coupling reaction of coumarin and aniline for the synthesis of indole fused coumarin derivatives. The one-pot method is operationally simple and molecular oxygen is used as sole oxidant. The target compounds are obtained in good yields from commercially available precursors.

ChemInform Abstract: The Possibilities of Palladium‐Catalyzed Aromatic Cyanation in Aqueous Media

AbstractReview: 54 refs.