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revised on 14.10.2020 and posted on 15.10.2020by Thomas De Dios Miguel, Nam Duc Vu, Marc Lemaire, Nicolas Duguet
The ring-opening of
epoxidized methyl oleate by aqueous H2O2 has been studied
using tungsten and molybdenum catalysts to form the corresponding fatty b-hydroxy hydroperoxides. It was found that tungstic acid and
phosphostungstic 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 b-hydroxy
hydroperoxides with 30-80% isolated yields (8 examples). These species were
fully characterized by 1H and 13C NMR, HPLC-HRMS and
their stability was studied by DSC. The thermal cleavage of the b-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 H2O2 and only generates water as a byproduct.