Electroactive molecular clips for host-guest chemistry

Date du colloque : 07/2013</p

Synthesis of molecular clips for the recognition of neutral guests

Date du colloque : 09/2014International audienc

Synthesis via direct (hetero)arylation polymerization, electrochemical and optical properties of poly (3,4-disubstituted)thiophenes

Some poly (3,4-disubstituted)thiophenes bearing both cyano and alkoxy or thioalkoxy groups have been synthesized by direct (hetero)arylation polymerization (DHAP) of 2-iodo-3,4-disubstituted thiophenes. The electron donor and acceptor properties of substituents in positions 3 and 4 allow to adjust the HOMO and LUMO levels. On the other hand, in order to avoid the polymer solubility problems, long branched or unbranched alkyl chains have also been introduced. Thus polymers with alkoxy groups have led to complete absorption in the wavelength range of the visible spectrum whereas in the presence of thioalkoxy groups, the absorption of the visible spectrum is only partial. Theoretical calculations have shown that sulphur creates torsions leading to a non-planar polymer chain

An Orthogonal Modular Approach to Macromonomers Using Clickable Cyclobutenyl Derivatives and RAFT Polymerization

A series of cyclobutene-based macromonomers derived from monomethyl ether poly(ethylene oxide) (PEO), poly(ethyl acrylate) (PEA), poly(N-isopropylacrylamide) (PNIPAM), and PEO-b-PNIPAM were synthesized by “click” copper-catalyzed azide−alkyne cycloaddition (CuAAC) and reversible addition−fragmentation chain transfer (RAFT) polymerization. First, original di- and trifunctional cyclobutene precursors with azido, alkyne and/or chain transfer agent were successfully obtained and fully characterized. Azido- and alkyne-functionalized cyclobutenes were then conjugated with modified PEO bearing azido or alkyne groups, resulting in cyclobutene-based PEOs in quantitative conversions as ascertained by NMR spectroscopy and MALDI−TOF mass spectrometry. The new chain transfer agent-terminated cyclobutene was used to mediate the RAFT polymerization of ethyl acrylate and N-isopropylacrylamide. Well-defined polymers with controlled molecular weights (Mn = 3700−11 500 g·mol−1) and narrow molecular weight distributions (PDI = 1.06−1.14) were thus obtained that retain the cyclobutene functionality, demonstrating the orthogonality of the RAFT process toward the cyclobutenyl insaturation. Combination of CuACC and RAFT polymerization was used to afford PEO-b-PNIPAM block copolymer functionalized by a cyclobutene end-group

Solvent free hydrostannation and Stille reactions using ionic liquid supported organotin reagents

Hydrostannation reactions were performed cleanly using ionic liquid supported organotin reagents. These green reducing agents were used both under free radical and palladium-catalyzed conditions. One of the new ionic liquid supported organotin reagents so obtained was evaluated successfully in Stille cross-coupling reactions to give aryl-substituted allylic alcohols in solvent free conditions

Cyclobutenyl macromonomers: Synthetic strategies and ring-opening metathesis polymerization

AbstractIn contrast to their (oxa)norbornenyl counterparts, cyclobutenyl derivatives have remained relatively unexplored in ring-opening metathesis polymerization (ROMP), despite ROMP of cyclobutene derivatives yields unsaturated polymers based on a strictly 1,4-polybutadiene backbone that is not easily attainable by other routes. This article summarizes work done in our group in the field of cyclobutenyl-capped macromonomers that are convenient building blocks for the synthesis of graft (bottle-brush) copolymers by ROMP via the so-called macromonomer (or grafting-through) route. Synthetic strategies employing orthogonal chemistries such as reversible deactivation radical polymerization techniques (atom transfer radical polymerization – ATRP, and reversible addition-fragmentation chain transfert (RAFT) polymerization) and recent developments using copper-catalyzed azide–alkyne cycloaddition click chemistry are highlighted. Furthermore, ROMP of the so-obtained macromonomers, including preliminary novel results regarding ROMP of cyclobutenyl-capped macromonomers prepared through RAFT polymerization and click chemistry are reported and discussed