Wissam Dayoub

Selective synthesis of 1-O-alkyl glycerol and diglycerol ethers by reductive alkylation of alcohols

1-O-alkyl glycerol and diglycerol ethers are obtained in high yields and high selectivity by catalytic reductive alkylation of glycerol and diglycerol with linear aldehydes in the presence of 0.5 mol% of Pd/C under 10 bars of hydrogen using a Bronsted acid as co-catalyst. All byproducts were identified. A mechanism for the reductive alkylation is proposed.

1-O-Alkyl (di)glycerol ethers synthesis from methyl esters and triglycerides by two pathways: catalytic reductive alkylation and transesterification/reduction

From available and bio-sourced methyl esters, monoglycerides or oleic sunflower refined oil, the corresponding 1-O-alkyl (di)glycerol ethers were obtained in both high yields and selectivity by two different pathways. With methyl esters, a reductive alkylation with (di)glycerol was realized under 50 bar hydrogen pressure in the presence of 1 mol% of Pd/C and an acid co-catalyst. A second two step procedure was evaluated from methyl esters or triolein and consisted of a first transesterification to the corresponding monoglyceride with a BaO/Al2O3 catalyst, then its reduction to the desired glycerol monoether with a recyclable heterogeneous catalytic system Pd/C and Amberlyst 35 under H2 pressure. In addition, a mechanism for the reaction was also proposed.

Selective Synthesis of 1‐O‐Alkyl(poly)glycerol Ethers by Catalytic Reductive Alkylation of Carboxylic Acids with a Recyclable Catalytic System

(Poly)glycerol monoethers were synthesized in good yield and selectivity by the catalytic reductive alkylation of glycerol, diglycerol, and triglycerol with readily available, cheap and/or bio-sourced carboxylic acids. The reaction was catalyzed by 1 mol % of Pd/C under 50 bar H(2) using an acid ion-exchange resin as a recyclable cocatalyst. The catalytic system was recycled several times, and a mechanism is proposed for this transformation.

1,2,3-Trimethoxypropane, a glycerol-based solvent with low toxicity: new utilization for the reduction of nitrile, nitro, ester, and acid functional groups with TMDS and a metal catalyst

1,2,3-Trimethoxypropane (1,2,3-TMP) was prepared from glycerol in one step in good yield and selectivity by phase transfer catalysis. According to OECD guidelines, a toxicity study was realized for this compound. It revealed that 1,2,3-TMP has a low acute toxicity, no skin sensitization, no mutagenicity and no ecotoxicity in an aquatic environment. This compound was also used as a solvent for the reduction of organic functions using either aluminium hydride or 1,1,3,3-tetramethyldisiloxane (TMDS) as a benign hydride source. In particular, a new process for the reduction of nitriles to amines in 2-MeTHF and in 1,2,3-TMP was developed, using TMDS in combination with copper triflate (Cu(OTf)2).

1,2,3-Trimethoxypropane and Glycerol Ethers as Bio-Sourced Solvents from Glycerol. Synthesis by Solvent-Free Phase-Transfer Catalysis and Utilization as an Alternative Solvent in Chemical Transformations

1,2,3‐Trimethoxypropane (2), 1‐alkoxy‐2,3‐dimethoxy‐propanes, and 1‐aryloxy‐2,3‐dimethoxypropanes were prepared in good yields and selectivity by solid–liquid phase‐transfer catalysis in the presence of an inorganic base and an ammonium salt as the phase‐transfer catalyst with no additional solvent. No heating was required, and the synthesis was easily performed under atmospheric pressure on a 150 g scale. For the preparation of 2, the conversion of glycerol was complete and the selectivity for the expected glycerol trimethylether was above 95 %. This product was utilized as a solvent in organic reactions such as transesterifications between glycerol and vegetable oil, organometallic reactions (Grignard‐ and Barbier‐type reactions), carbon–carbon coupling reactions (Suzuki, Sonogashira, Heck), and in etherification reactions by dehydrogenative alkylation. The solvent showed interesting properties for the solubilization of polymers.

Environmentally benign metal triflate-catalyzed reductive cleavage of the C–O bond of acetals to ethers

A protocol is described for the reductive cleavage of the C–O bond of aromatic and aliphatic acetals to ethers catalyzed by Cu(OTf)2 or Bi(OTf)3 at room temperature in excellent yields, without affecting aromatic rings, nitro, nitrile, ester and hydroxyl groups. This protocol represents an improvement in terms of atom economy compared to the previous methods, by distinctly decreasing the amount of the reducing reagent, 1,1,3,3-tetramethyldisiloxane (TMDS), and using a small amount of catalyst.