Methyltrioxorhenium (MTO)
Methyltrioxorhenium is commercially available and stable in air. MTO is an exceptionally versatile oxygen transfer catalyst with hydrogen peroxide as terminal oxidant. A drawback is the limited stability in water.
Recent Literature
A convenient and efficient oxidation of hydroxylated and methoxylated
benzaldehydes and acetophenones to the corresponding phenols uses hydrogen
peroxide and methyltrioxorhenium as catalyst in ionic liquids [bmim]BF4
and [bmim]PF6.
R. Bernini, A. Coratti, G. Provenzano, G. Fabrizi, D. Tofani, Tetrahedron, 2005,
61, 1821-1825.
Methyltrioxorhenium (MTO) catalyzes an epoxidation of alkenes with 30%
aqueous hydrogen peroxide. The addition of 1-10 mol % of 3-cyanopyridine
increases the system's efficiency resulting in high isolated yields of the
corresponding epoxides. Alkenes yielding epoxides more sensitive to nucleophilic
ring opening require a mixture of 3-cyanopyridine and pyridine.
H. Adolfsson, C. Copéret, J. P. Chiang, A. K. Yudin, J. Org. Chem., 2000,
65, 8651-8658.
In MTO-catalyzed epoxidation, aqueous hydrogen peroxide is typically added
dropwise to a dichloromethane solution of the olefin, pyrazole as accelerant,
and MTO. The use of sodium percarbonate (SPC) offers a slow
release of hydrogen peroxide, that can be accelerated using trifluoroacetic acid.
A. R. Vaino, J. Org. Chem., 2000,
65, 4210-4212.
Homoallylic alcohols were efficiently epoxidized to the corresponding 3,4-epoxy
alcohols in excellent yields in the presence of methyltrioxorhenium (MTO) as
catalyst, aqueous hydrogen peroxide as the terminal oxidant, and
3-methylpyrazole as an additive. Organic solvent-free conditions accelerate the
reaction.
S. Yamazaki, J. Org. Chem., 2012,
77, 9884-9888.
Methyltrioxorhenium (MTO) catalyzes an oxidation of methyl trimethylsilyl ketene
acetals with urea hydrogen peroxide to afford α-hydroxy and α-siloxy esters. On
treatment with potassium fluoride, the α-hydroxy esters are obtained in high
yields.
S. Stanković, J. H. Espenson, J. Org. Chem., 2000,
65, 5528-5530.
Sodium percarbonate is an ideal and efficient oxygen source for the oxidation of
tertiary nitrogen compounds to N-oxides in excellent yields in the
presence of various rhenium-based catalysts under mild reaction conditions.
S. L. Jain, J. K. Joseph, B. Sain, Synlett, 2006,
2661-2663.
Sodium percarbonate is an ideal and efficient oxygen source for the oxidation of
tertiary nitrogen compounds to N-oxides in excellent yields in the
presence of various rhenium-based catalysts under mild reaction conditions.
S. L. Jain, J. K. Joseph, B. Sain, Synlett, 2006,
2661-2663.
A general, high yielding, and user and environmentally friendly catalytic
oxidation procedure for the chemoselective conversion of imines to nitrones is
reported.
G. Soldaini, F. Cardona, A. Goti, Org. Lett., 2007,
9, 473-476.