Direct C sp(2)-H and C sp(3)-H Arylation Enabled by Heterogeneous Palladium Catalysts

BIOVERT+LDJThis review gives an overview of direct C-H arylation catalyzed by heterogeneous Pd catalysts. The efficiency of the different forms of heterogeneous Pd catalysts is discussed with a critical view of the transformations attainable. If experimental evidence is provided, mechanistic considerations on the true nature of the catalysis, that is, heterogeneous versus homogeneous, are discussed as well

Copper(II)-phenanthroline hybrid material as efficient catalyst for the multicomponent synthesis of 1,2,3-triazoles via sequential azide formation/1,3-dipolar cycloaddition

SSCI-VIDE+CDFA+LDJInternational audienceA copper(II)-phenanthroline hybrid material based on the SBA-15 architecture was prepared using a two-step synthesis through co-condensation of 5-[N,N-bis-3-(triethoxysilyl)propyl]ureyl-1,10phenanthroline with tetraethoxysilane, followed by coordination of Cu(OAc)(2). The obtained hybrid material, Cu(II)phen@SBA-15, was fully characterized, at each stage of the preparation, by means of bulk and molecular techniques to assess both textural and structural catalyst features using XRD, XPS, EPR, HRTEM, SEM, solid-state NMR UV-vis and IR analytical tools. The characterization results altogether confirmed the structural integrity of the mesoporous host and the successful anchoring of the copper-phenanthroline complex as discrete mononuclear Cu(II)L species. The catalytic performances of Cu(II)phen@SBA-15 were evaluated in the aqueous 1,3-dipolar cycloaddition of azides with alkynes using a multicomponent one-pot synthesis where organic azides were produced in situ from organic bromide (or aryl diazonium salts or epoxides), providing for safer synthetic technologies. The catalyst proved to be highly active under mild reaction conditions (0.5 mol%, 70 degrees C) over a broad range of substrates, providing 1,4-disubstituted-1,2,3-triazoles in high yields. (C) 2016 Elsevier B.V. All rights reserved

Photoresponsive cellulose paper as a molecular printboard for covalent printing

This contribution unveils and defines the concept of covalent printing onto cellulose paper through the support of a simple and efficient strategy. A photoresponsive cellulose paper bearing disulfide functional groups was created as a molecular printboard for spatio-temporal writing through thiol-X ligation of functional inks upon light irradiation. This strategy using molecular inks in a modular way culminated with the creation of patterns with a high resolution. Hidden covalent writing to the naked eyes was developed through the use of coumarin-based inks while the use of colored inks containing a rhodamine backbone established an uncovered pH-responsive covalent printing, both strategies can potentially find applications in the formation of anti-counterfeiting devices

A highly selective colorimetric and fluorescent chemosensor for Cr2+ in aqueous solutions

A new rhodamine-based chemosensor was synthetized through a modified copper-catalyzed [3+2]-cycloaddition of an azidocoumarin with an alkynyl-rhodamine. Its sensing properties toward various metal cations in aqueous solutions were investigated by colorimetric changes, UV vis and fluorescence spectroscopies. The sensor exhibited a high selectivity for Cr2+ over Cr3+ and other divalent cations such as Cu2+, Mg2+, Zn2+, Ca2+, Cd2+, Co2+, Hg2+. and Ni2+. The linear range of detection by fluorescence spectroscopy is 0.07-3.5 mM, with a detection limit of ca. 64 mu M. The binding mode of Cr2+ with the sensor was rationalized through experimental evidences. (C) 2017 Elsevier Ltd. All rights reserved

Sustainable heck-matsuda reaction with catalytic amounts of diazonium salts: An experimental and theoretical study

cited By 31International audienceThe palladium-catalyzed Heck-Matsuda reaction with a catalytic amount of an in-situ-generated diazonium salt proceeded under mild and sustainable conditions. The reaction proceeded at room temperature, under base-free conditions, and only generated tBuOH, H 2O, and N 2 as by-products. Ortho-substituted diazonium salts were more-efficiently coupled to methyl acrylate than their corresponding paraisomers, which required the addition of anisole as an additive. In support of these experimental data, we carried out theoretical studies to gain a deeper understanding of these reaction outcomes. © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Writing and erasing hidden optical information on covalently modified cellulose paper

An unprecedented strategy for preparing photoresponsive cellulose paper enabling the storage of short-lived optical data by covalent photopatterning is disclosed. An ab initio design hinting that the covalent grafting of coumarins on the paper could yield valuable photoresponsive units was first performed. Second, light sensitive paper that can be reversibly altered upon irradiation at a specific wavelength was prepared by covalent surface functionalization with coumarins. Third, the validity of this strategy is demonstrated using the photolithography of several gripping patterns such as a dynamic QR code

Room-temperature, ligand- and base-free heck reactions of aryl diazonium salts at low palladium loading: Sustainable preparation of substituted stilbene derivatives

cited By 65International audienceThe Pd(OAc)2-catalyzed Heck reaction of aryl diazonium salts with 2-arylacrylates led to cis-stilbenes with good to excellent stereoselectivity. The environmentally friendly protocol developed in this work features low palladium loading in technical-grade methanol at room temperature under base-, additive-, and ligand-free condi-tions. The same protocol applied to simple Heck coupling of aryl diazonium salts with methyl acrylate allows as-tonishingly low palladium loading, down to 0.005 mol %. The stereoselectivity experimentally observed for the synthesis of cis-stilbenes has been rationalized by DFT calculations. Moreover, the role of methanol in promoting the reaction has been clarified by a computational study. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA

Chelation-assisted cross-coupling of anilines through in situ activation as diazonium salts with boronic acids under ligand-, base-, and salt-free conditions

cited By 11International audienceWe describe the coupling of anilines with aryl boronic acids, under ligand-, base-, and salt-free conditions at room temperature. This new reaction proceeds through the formation of an aryl palladium alkoxo complex, which allows the transmetalation step with aryl boronic acids without any external base. Importantly, this sustainable procedure generates only environmentally friendly byproducts such as tBuOH, H2O, N2, and B(OH)3. The reaction mechanism has been deeply investigated through experimental and theoretical studies. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim