Chain transfer kinetics of acid/base switchable n-aryl- n-pyridyl dithiocarbamate RAFT agents in methyl acrylate, n-vinylcarbazole and vinyl acetate polymerization

This is an accepted manuscript of an article published by American Chemistry Society in Macromolecules on 14/05/2012, available online: https://doi.org/10.1021/ma300616g ©American Chemical Society. The accepted version of the publication may differ from the final published version.The structures of the "Z" and "R" substituents of a RAFT agent (Z-C(S)S-R) determine a RAFT agent's ability to control radical polymerization. In this paper we report new acid/base switchable N-aryl-N-pyridyl dithiocarbamates (R = -CH 2CN, Z = -N(Py)(Ar)) which vary in substituent at the 4-position of the aryl ring and the use of these to control molecular weight and dispersity. In their protonated form, the new RAFT agents are more effective in controlling polymerization of the more activated monomer, methyl acrylate (MA), whereas in their neutral form they provide more effective control of the polymerization of less activated monomers, N-vinyl carbazole (NVC) and vinyl acetate (VAc). For each polymerization, the apparent chain transfer coefficient (C trapp) shows a good correlation with Hammett parameters. Dithiocarbamates with more electron-withdrawing aryl ring substituents have the higher C trapp. This demonstrates the influence of polar effects on C trapp and supports the hypothesis that the activity of these RAFT agents is determined by the availability of the lone pair of the dithiocarbamate nitrogen.The authors gratefully acknowledge the Capability Development Fund of CSIRO Materials Science and Engineering for financial support.Published versio

Transition Metal-Catalysed, Direct and Site-Selective N1-, C2-or C3-Arylation of the Indole Nucleus: 20 Years of Improvements

Joucla, Lionel Djakovitch, LaurentThe direct and site-selective transition metal-catalysed N1-, C2- or C3-arylations of indoles have been the subject of almost continuous improvements since their discovery in early 1980s. This research area is mainly motivated by the biological relevance of this class of compounds in order to propose catalytic alternative syntheses to the well known methodologies involving the formation of the indole ring like the Fischer, Larock, Cacchi, Lautens etc. reactions. Since the late 1990s it has experienced new impulses related to the intensive development of catalytic C-H activation. Today, through the intensive studies of Buchwald and Hartwig, the N1-arylation of indoles has reached sufficient maturity for both academic and industrial applications. On the other hand, the selective C2- or C3-arylation of indoles, initiated by Ohta in the middle 1980s, has become a hot research area these last years following the reports of Sames. Surprisingly, only few reports concern the use of heterogeneous catalysts; however, the application of these emerging methodologies seems to be related to the discovery of industrially attractive systems

First heterogeneously Pd-catalysed C3-arylation of free indoles

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First heterogeneously palladium-catalysed fully selective C3-arylation of free NH-indoles

International audienceA simple heterogeneously palladium-catalysed procedure for the selective C3-arylation of indoles is reported. Under relatively standard reaction conditions (Pd-catalyst, K2CO3, dioxane, reflux), using only 1 mol % [Pd(NH3)4]/NaY as the catalyst, indoles substituted or not at position 2 gave up to 92% conversion (i.e., 85% isolated yield) towards the expected C3-arylated indole

Synthesis of 3-Arylpropenal and 3-Arylpropionic Acids by Palladium Catalysed Heck Coupling Reactions: Scopes and Limitations

Djakovitch, Laurent Pinel, CatherineSeveral classical methods were described for the selective synthesis of cinnamaldehyde derivatives and 3-arylpropionic acids but their applicability remains limited due to the difficult and costly synthesis of the starting materials. Since few years, palladium catalyzed procedure has been reported. Whatever they use homogeneous or heterogeneous palladium catalysts, these catalytic methods offer viable environmental friendly alternatives to stoechiometric methods particularly since they generally required a single reaction step starting from simple substrates. Some of these new methods are really considered as green alternatives since they use heterogeneous easily separable (and recyclable) palladium catalysts

New homogeneously and heterogeneously [Pd/Cu]-catalysed C3-alkenylation of free NH-indoles

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