Christophe Darcel

Efficient and selective N -alkylation of amines with alcohols catalysed by manganese pincer complexes

Borrowing hydrogen (or hydrogen autotransfer) reactions represent straightforward and sustainable C–N bond-forming processes. In general, precious metal-based catalysts are employed for this effective transformation. In recent years, the use of earth abundant and cheap non-noble metal catalysts for this process attracted considerable attention in the scientific community. Here we show that the selective N-alkylation of amines with alcohols can be catalysed by defined PNP manganese pincer complexes. A variety of substituted anilines are monoalkylated with different (hetero)aromatic and aliphatic alcohols even in the presence of other sensitive reducible functional groups. As a special highlight, we report the chemoselective monomethylation of primary amines using methanol under mild conditions.

Ferrocenyl glycopeptides as electrochemical probes to detect autoantibodies in multiple sclerosis patients' sera.

Glycopeptide analogues of CSF114(Glc), modified at N‐terminus with new ferrocenyl carboxylic acid and a new ferrocenyl‐thiphosphino amino acid, were used to implement a new electrochemical biosensor for autoantibody detection in multiple sclerosis. The ferrocenyl moiety of these “electrochemical probes” did not affect autoantibody recognition both in SP‐ELISA and in inhibition experiments. By electrochemical monitoring the interactions of the modified peptides Fc‐CSF114(Glc) and 4‐FcPhP(S)Abu‐CSF114(Glc) with the autoantibodies, we demonstrated that autoantibodies could be detected with a sensitivity comparable to ELISA method. The new electrochemical probes can be proposed to characterize autoantibodies as biomarkers of multiple sclerosis by a simple, rapid, and reproducible cyclic voltammetry‐based diagnostic methodology.

MONO AND DIPHOSPHINE BORANE COMPLEXES GRAFTED ON POLYPYRROLE MATRIX: DIRECT USE AS SUPPORTED LIGANDS FOR RH AND PD CATALYSIS

Abstract A new versatile method for the synthesis of supported mono and diphosphines on polypyrrole matrix is described, based on the protective borane complexation of the phosphorus atom. For the first time, the unknown alkylation of a diphosphine ethano bridge, was obtained with near yield close to 70%, leading to its derivative 8 bearing the polymerizable pyrrole group on a side chain. The different supported mono and diphosphine boranes 12–15 have been applied with success in palladium-catalyzed allylation, cross-coupling reaction and in rhodium-catalyzed hydrogenation. It is of particular interest that supported phosphine boranes can be used without previous decomplexation, forming in situ the catalytically active species from Pd(OAc)2 or RhCl3. Moreover, the recoverable polymer could be used again in rhodium-catalyzed hydrogenation with a very good efficiency after several turn-overs. Nethertheless, we may point out that with palladium catalysis, the addition of Pd(dba)2 was necessary to recover the catalytic activity. These results demonstrate that the phosphine borane complexes are key precursors for the synthesis of functionalized mono and diphosphines, and for their direct use in generating catalysts.

Transfer Hydrogenation of Carbonyl Derivatives Catalyzed by an Inexpensive Phosphine-Free Manganese Precatalyst

A very simple and inexpensive catalytic system based on abundant manganese as transition metal and on an inexpensive phosphine-free bidendate ligand, 2-(aminomethyl)pyridine, has been developed for the reduction of a large variety of carbonyl derivatives with 2-propanol as hydrogen donor. Remarkably, the reaction proceeds at room temperature with low catalyst loading (down to 0.1 mol %) and exhibits a good tolerance toward functional groups. High TON (2000) and TOF (3600 h-1) were obtained.

CHAPTER 4:Iron-Catalyzed Cross-Dehydrogenative-Coupling Reactions

In transition metal catalyzed cross-dehydrogenative-coupling (CDC) reactions for the efficient building of C–C bonds from two C–H bonds, iron is an inexpensive and earth abundant metal that has attracted increasing interest during the last few years. Using commercially available iron salts (such as FeCl3, FeCl2, Fe(OAc)2), or organometallic precursors (such as Fe2(CO)9) as catalysts, in the presence of stoichiometric amounts of oxidants such as tert-butyl hydroperoxide, di-tert-butyl peroxide, DDQ, TEMPO oxoammonium salts, or even oxygen, sp3– sp3, sp3–sp2, sp3–sp and sp2–sp2 C–C bond formation can be efficiently performed. This is a breakthrough in terms of greener chemistry! Interestingly, this iron-catalyzed methodology also allows more sophisticated heterocyclic and/or polycyclic compounds to be prepared in tandem sequences.