Yann Raoul

Bleaching Earths as Powerful Additives for Ru-Catalyzed Self-Metathesis of Non-Refined Methyl Oleate at Pilot Scale

A practical and cost-effective ruthenium-catalyzed self-metathesis of non-refined methyl oleate (85u2009%) derived from very high oleic sunflower oils was demonstrated at pilot scale using a robust and kg-scale commercially available SIPr-M71 pre-catalyst. The simple addition of 1u2005wtu2009% bleaching earths (Tonsil 110FF) to a thermally pretreated oil could efficiently prevent catalyst deactivation. Remarkably, without the need for filtration, the catalytic system was able to achieve a turnover number (TON) of more than 744u2009000 at a catalyst loading of only 1u2005ppm. At large scale (up to 200u2005kg), the equilibrium of the self-metathesis reaction was reached within 1u2005hour at 50u2009°C under neat conditions at a very low 5u2005ppm catalyst loading to produce the expected primary metathesis products (PMP), that is, 9-octadecene and dimethyl-9-octadecenoate, with a productive TON of 94900.

Stereoretentive Olefin Metathesis Made Easy: In Situ Generation of Highly Selective Ruthenium Catalysts from Commercial Starting Materials

The in situ preparation of highly stereoretentive ruthenium-based metathesis catalysts is reported. This approach completely avoids the isolation of intermediates and air-sensitive catalysts, thus allowing for the rapid access and evaluation of numerous dithiolate Ru catalysts. A procedure was established to perform cross-metathesis reactions without the use of a glovebox, and on a small scale even Schlenk techniques are not required. Consequently, the chemistry displayed in this report is available to every practicing organic chemist and presents a powerful approach for the identification of new stereoretentive catalysts.

Evaluation of the Effect of Chemical or Enzymatic Synthesis Methods on Biodegradability of Polyesters

This work compares the biodegradability of polyesters produced by an esterification reaction between glycerol and oleic di-acid (D 18:1) issued from green chemical pathways, via either classical thermo-chemical methods, or an enzymatic method using the immobilized lipase of Candida antartica B (Novozym 435). An elastomeric polymer synthesized by enzymatic catalysis is more biodegradable than an elastomeric thermo-chemical polyester synthesized by a standard chemical procedure. This difference lies in percentage of the dendritic motifs, in values of the degree of substitution, and certainly in cross-links inducing an hyper-branched structure less accessible to the lipolytic enzymes in a waste treatment plant. However, when the elastomeric polymer synthesized by enzymatic catalysis is processed at high temperature as required for certain industrial applications, it presents an identical rate of biodegradation than the chemical polyester. The advantages of the thermo-chemical methods are greater speed and lower cost. Enzymatic synthesis appears be suited to producing polyesters, devoid of metallic catalysts, which must be used without processing at high temperature to keep a high biodegradability.