Methyltrioxorhenium/pyrazole—A highly efficient catalyst for the epoxidation of olefins

Methyltrioxorhenium Catalysis in Nonconventional Solvents: A Great Catalyst in a Safe Reaction Medium

“…The epoxidation of olefins with the MTO/ H 2 O 2 system is usually performed in CH 2 Cl 2 , in which the catalytically active peroxorhenium species shows a high reactivity (for a Review on the epoxidation of olefins in conventional solvents see [9e]). As already pointed out, to avoid the formation of diols as side-products different heterocyclic amines, including pyridine, [55] pyrazole, [56] and 3-methyl pyrazole, [57] can be used as additives, in order to neutralize the acidic properties of MTO as well as to tune the selectivity of the oxidation reaction. [58] Recently, Yamazaki reported the efficient organic-solvent-free epoxidation of olefins with H 2 O 2 , catalyzed by MTO and heterocyclic amines (Scheme 30).…”

Chromophoric Lewis Base Adducts of Methyltrioxorhenium: Synthesis, Catalysis and Photochemistry

“…The compounds obtained are stable to air, both in the solid state and in dichloromethane solution. Selected 1 H and 13 C NMR spectroscopic data of compounds 8-14 are shown in Table 1. The proton signals of the MTO methyl group of the complexes are considerably shifted to higher field, indicating the strength of the Re-N bond.…”

Transition Metal‐Catalyzed Epoxidation of Alkenes

“…This can be beneficial for slow-reacting substrates, where N-oxidation would compete with alkene epoxidation. The Herrmann group introduced an improvement to the Sharpless system by employing pyrazole as an additive [75]. Compared to pyridine, pyrazole is a less basic heterocycle (pK a ¼ 2.5) and does not undergo N-oxidation by the MTO/H 2 O 2 system.…”