Ethers reaction with chromium trioxide

The mixture of chromium trioxide with one equivalent of trimethylsilyl chloride, with no solvent added, results in the formation of an explosive red liquid that is soluble in dichloromethane or tetrachloromethane.428 It is suggested, with no spectroscopic evidence, that it consists of trimethylsilyl chlorochromate [Me3Si-0-Cr(0)2-Cl]. This compound, which can safely be used in organic solvents, is able to oxidize alcohols to aldehydes or ketones, and interacts with r-butyldimethylsilyl ethers producing deprotection, followed by oxidation of the liberated alcohol.138 Compounds analogue to trimethylsilyl chlorochromate are also able to oxidize alcohols, although they possess lesser reactivity. They can be prepared by reaction of chromium trioxide with dimethyldichlorosilane and diphenyldichlorosilane.428b... 

The relative reactivity of primary and secondary positions adjacent to oxygen can be strongly dependent on the nature of the oxidant. For example, treatment of the methyl ethers (8) and (10) with chromium trioxide in acetic acid leads to the formation of the formates (9) and (11), respectively (equations 13 and 14). In direct contrast, n-decyl methyl ether is oxidized exclusively to methyl n-decanoate (83% yield) by ruthenium tetroxide (equation 11). Under similar reaction conations, 3 -cholestanol methyl ether gives cholestan-3-one as the mqjor product, togedier with traces of the corresponding formate. Therefore, at least in the case of ruthenium tetroxide, primary positions appear to be more reactive than tertiary. 

Oxidation of the trihydroxypropyl compound 7 or the aldehydes 38 and 40 with chromium trioxide in acetic acid or 50% sulfuric acid furnishes the 3-carboxylic acids, which readily decarboxylate to the 3-unsubstituted compounds at their melting points. " In contrast, the 3-methyl-l-phenyl compoimd is not appreciably attacked by chromiiun trioxide, potassium permanganate, or selenium dioxide. Chromyl chloride oxidation of 7 does not give the aldehyde 38 but apparently provides the tetraflavazolyl ether 41. The inertness of the 3-methyl group is emphasized by its stability toward bromine and its lack of reaction with benzaldehyde." ... 

CrOs. Chromium oxide can also oxidize benzylic positions., as in the Etard reaction (see sec. 3.8.E). When 391 was treated with chromium trioxide in acetic acid, an 85% yield of 392 was obtained, as part of Pan s synthesis of (-)-6,7-dehydrofeiruginyl methyl ether. l... 

The reaction of hexafluorobenzene with potassium p-cresoxide (4 molar equivalents) in dimethylformamide yields 1,4-bis-p-cresoxytetrafluoro-benzene (54%) oxidation of this with chromium trioxide gives the diacid (69) (83%), also obtainable from hexafluorobenzene and the dipotassium salt ofp-hydroxybenzolc acid (67%). A number of conventional derivatives of the diacid (69) are described, and its orientation is established by decarboxylation (CuSOg-quinoline, 285 °Q to the known 2,3,5,6-tetrafluoro-l,4-diphenoxybenzene. The preparation in good yield of several polyfluoro-(diphenyl ethers) from polyfluoroarenes and sodium polyfluorophenoxides... 

---