Nicolas Oger

Continuous-flow Heck-Matsuda reaction: homogeneous versus heterogeneous palladium catalysts.

This study describes extensive investigations of the Heck-Matsuda reaction carried out by continuous-flow chemistry between aryl diazonium salts generated in situ and methyl acrylate. Our optimized procedures enable sequential aniline diazotization/palladium-catalyzed Heck-Matsuda reaction using either Pd(OAc)2 or PdEnCat 30 as respectively a homogeneous or a heterogeneous source of palladium. This safe chemistry that does not require the handling of hazardous aryl diazonium salts involves inexpensive reagents and solvents, under ligand- and base-free conditions.

Handling diazonium salts in flow for organic and material chemistry

This review gives an overview of transformations involving the use of diazonium salts in flow. The efficiency of the strategies is critically discussed with a special emphasis on the design of the flow devices. If comparative studies with batch chemistry is provided, the input of flow chemistry with regard to the reaction yields and safety issues is discussed as well.

Heterogeneous Palladium Catalysts for Suzuki–Miyaura Coupling Reactions Involving Aryl Diazonium Salts

This Minireview gives a complete overview of the Suzuki–Miyaura coupling reaction involving aryl diazonium salts catalyzed by heterogeneous palladium catalysts. For each process, the preparation and the properties of the heterogeneous catalysts as well as the catalytic system are critically discussed, providing their strengths and weaknesses.

Palladium Nanoparticles Supported on Sulfonic Acid Functionalized Silica as Trifunctional Heterogeneous Catalysts for Heck and Suzuki Reactions

The arylation of acrylates and boronic acids with anilines, through in situ generated aryl diazonium salts, was successfully achieved by using trifunctional heterogeneous catalysts bearing Brønsted acid and metal active sites. The trifunctional materials were prepared by adsorption of palladium nanoparticles, generated by reduction of a solution of Pd(OAc)2 onto a commercially available sulfonic acid functionalized silica. These new trifunctional catalysts act as a 1) proton donor for the diazotization step, 2) counterion for the diazonium salt, and 3) Pd source for the coupling step. This unprecedented strategy, features mild and safe conditions as hazardous aryl diazonium salts are generated in situ and only produces environmentally friendly byproducts such as tBuOH, H2O, and N2.

Graphene-promoted acetalisation of glycerol under acid-free conditions

Serendipity led us to unveil unexpected and uncovered properties of graphene for the acetalisation of glycerol with both aldehydes and ketones, furnishing an acid-free process for fuel bio-additive candidates. Mechanistic studies ruled out the intervention of residual acidic species or metallic cations at the surface of graphene, and therefore, the peculiar electronic properties of graphene are most probably responsible for this unforeseen reactivity. Recycling studies revealed the robustness of graphene under the experimental conditions since only a marginal erosion of the reaction yield was observed after six cycles.

An Autonomous Self-Optimizing Flow Reactor for the Synthesis of Natural Product Carpanone

A modular autonomous flow reactor combining monitoring technologies with a feedback algorithm is presented for the synthesis of the natural product carpanone. The autonomous self-optimizing system, controlled via MATLAB, was designed as a flexible platform enabling an adaptation of the experimental setup to the specificity of the chemical transformation to be optimized. The reaction monitoring uses either online high pressure liquid chromatography (HPLC) or in-line benchtop nuclear magnetic resonance (NMR) spectroscopy. The custom-made optimization algorithm derived from the Nelder-Mead and golden section search methods performs constrained optimizations of black-box functions in a multidimensional search domain, thereby assuming no a priori knowledge of the chemical reactions. This autonomous self-optimizing system allowed fast and efficient optimizations of the chemical steps leading to carpanone. This contribution is the first example of a multistep synthesis where all discrete steps were optimized with an autonomous flow reactor.