2,5‐Diformylfuran (DFF) was obtained by heating a solution of 5‐(hydroxymethyl)furfural in DMSO. The addition of acids or salts improved the selectivity, especially if bromides were employed. Good yields of DFF were obtained with HBr or NaBr as the catalyst. One‐pot procedures were developed from fructose, which led to DFF in medium yields. This transformation occurs through the formation of 5‐(bromomethyl)furan‐2‐carbaldehyde followed by a Kornblum‐type reaction. In the presence of bromide salts, the in situ formation of the catalyst involves the thermolysis of DMSO and the association of the resulting strong acids with the bromides.
4,5‐Diazafluorenone was found to promote the dehydrogenative Heck reaction of furans and thiophenes with hindered alkenes. High stereoselectivity was achieved in the synthesis of β,β‐diaryl α,β‐unsaturated alkenes. A mechanism, based on ESI‐MS studies, kinetic experiments, and competitive reactions, was proposed. The ligand influences C–H bond activation, insertion of the alkenes, the stereodetermining step, and the aerobic regeneration of the catalyst.
Ligand-Promoted Reactivity of Alkenes in Dehydrogenative Heck Reactions of Furans and Thiophenes. -4,5-Diazafluorenone is found to be an effective ligand for the dehydrogenative Heck reaction of cinnamic acid derivatives or stilbenes with thiophenes and furanes. According to kinetic and competitive experiments, the ligand has an influence on all steps of the catalytic cycle. -(VASSEUR, A.; LAUGEL, C.; HARAKAT, D.; MUZART, J.; LE BRAS*, J.; Eur. J. Org. Chem. 2015, 5, 944-948, http://dx.doi.org/10.1002/ejoc.201403475 ; Unite Mixte Rech., CNRS, Univ. Reims-Champagne-Ardenne, F-51687 Reims, Fr.; Eng.) -H. Haber 25-080
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