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Chromium reagents silica support

Oxidation with hexavalent chromium usually leads to complex product mixtures.641 However, certain Cr(VI) reagents [Cr02(00CCCl3)2,642 Cr03 supported on silica,643 bistriphenylsilyl chromate644], and a Cr(V) complex,645 may be used to form carbonyl compounds. [Pg.482]

The procedure is commendable for its sinq>licity, reduced toxicity (chromium in all its oxidation states is carcinogenic) and achieves good yields of ketones from alcohol, for example, octan-2-ol is oxidized into octan-2-one (92%), cyclohexanol into cyclohexanone (90%) and menthol into menthone (98%). Pyridinium chromate is also a well-known oxidant for allylic oxidations. As a silica gel supported reagent, this is turned into an efficient alcohol oxidant that will leave acid-labile functions unscathed. Another advantage of the reagent is the long shelf-life of more than a year. These solid-supported oxidants also greatly facilitate pr uct work-up, when compared with their solution counterparts. [Pg.845]

Several references have appeared on the use of solid-phase oxidants. Solid potassium permanganate-copper sulphate mixtures oxidize secondary alcohols to ketones in high yield, and pyridinium chromate or chromic acid on silica gel are described as convenient off-the-shelf reagents for oxidation of both primary and secondary alcohols. Anhydrous chromium trioxide-celite effects similar transformations only when ether is present as co-solvent. An excellent review, with over 400 references, on supported oxidants covers the use of silver carbonate-celite, chromium trioxide-pyridine-celite, ozone-silica, chromyl chloride-silica, chromium trioxide-graphite, manganese dioxide-carbon, and potassium permanganate-molecular sieve. [Pg.27]


See other pages where Chromium reagents silica support is mentioned: [Pg.208]    [Pg.253]    [Pg.160]    [Pg.496]    [Pg.236]    [Pg.237]    [Pg.236]    [Pg.237]    [Pg.524]    [Pg.149]    [Pg.236]    [Pg.237]    [Pg.693]    [Pg.65]   
See also in sourсe #XX -- [ Pg.844 ]

See also in sourсe #XX -- [ Pg.844 ]

See also in sourсe #XX -- [ Pg.7 ]

See also in sourсe #XX -- [ Pg.7 ]

See also in sourсe #XX -- [ Pg.844 ]




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Chromium reagents

Chromium supported

Silica support

Silica supported chromium

Silica-supported reagents

Supported reagents

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