Biobased Aldehydes from Fatty Epoxides through Thermal Cleavage of β‐Hydroxy Hydroperoxides**

Abstract

The ring-opening of epoxidized methyl oleate by aqueous H 2 O 2 has been studied using tungsten and molybdenum catalysts to form the corresponding fatty β-hydroxy hydroperoxides. It was found that tungstic acid and phosphotungstic acid gave the highest selectivities (92-93 %) towards the formation of the desired products, thus limiting the formation of the corresponding fatty 1,2-diols. The optimized conditions were applied to a range of fatty epoxides to give the corresponding fatty βhydroxy hydroperoxides with 30-80 % isolated yields (8 examples). These species were fully characterized by 1 H and 13 C NMR spectroscopy and HPLC-HRMS, and their stability was studied by differential scanning calorimetry. The thermal cleavage of the β-hydroxy hydroperoxide derived from methyl oleate was studied both in batch and flow conditions. It was found that the thermal cleavage in flow conditions gave the highest selectivity towards the formation of aldehydes with limited amounts of byproducts. The aldehydes were both formed with 68 % GC yield, and nonanal and methyl 9-oxononanoate were isolated with 57 and 55 % yield, respectively. Advantageously, the overall process does not require large excess of H 2 O 2 and only generates water as a byproduct.

The Chemistry of β‐Hydroxy Hydroperoxides

“…Recently, Duguet et al have reported the thermal cleavage of fatty β-hydroxy hydroperoxides in continuous flow conditions. [63] A solution of a β-hydroxy hydroperoxide derived from methyl oleate in CH 3 CN was pumped through an oven set at 300°C (no cleavage has been observed below this temperature) and the products were recovered upon cooling the outlet of the system. At 300°C, with a flow rate of 1 mL min À 1 , the residence time was about 3 min and the cleavage was complete.…”

“…[63,95] Some differential scanning calorimetry (DSC) analyses have been reported on neat fatty β-hydroxy hydroperoxides. [63] For example, the DSC decomposition enthalpy was found to be À 611 J.g À 1 (À 211 KJ.mol À 1 ) with a peak at 107°C, for the hydroperoxide derived from epoxidized methyl oleate. Moreover, DSC traces are very broad indicating a gradual release of heat, similar to fatty ozonides, thus showing a limited risk of explosion for such species.…”

“…Recently, Duguet et al . have reported the preparation of fatty β‐hydroxy hydroperoxides [63] . The reaction was carried out using aqueous 50 %‐H 2 O 2 (1.1 equiv) in the presence of phosphotungstic acid (PTA, 0.1 mol%) (Scheme 35).…”

“…This could lead to the formation of byproducts during purification. In contrast, this property can be advantageously used for the preparation of high‐added value compounds from biomass feedstocks [63,95] . Some differential scanning calorimetry (DSC) analyses have been reported on neat fatty β‐hydroxy hydroperoxides [63] .…”

“…In contrast, this property can be advantageously used for the preparation of high‐added value compounds from biomass feedstocks [63,95] . Some differential scanning calorimetry (DSC) analyses have been reported on neat fatty β‐hydroxy hydroperoxides [63] . For example, the DSC decomposition enthalpy was found to be −611 J.g −1 (−211 KJ.mol −1 ) with a peak at 107 °C, for the hydroperoxide derived from epoxidized methyl oleate.…”