Chromium Trioxide (CrO3)
Product Manager：Nick Wilde
Chromium trioxide serves as a potent oxidizing agent, exhibiting insolubility in a majority of organic solvents and a propensity to detonate when in contact with organic compounds and solvents. When dissolved in water, it undergoes transformation into chromic acid and anhydrides, which subsequently yield commercially accessible salts, including sodium dichromate (Na2Cr2O7) and pyridinium dichromate.
Although chromium trioxide is soluble in certain solvents like tert-butyl alcohol, pyridine (as seen in the Sarett and Collins Reagents), and acetic anhydride, it is crucial to adhere strictly to prescribed procedures during handling, as these solutions have an explosive tendency. However, a solution of chromium trioxide dissolved in aqueous sulfuric acid can be safely combined with acetone, known as the Jones Reagent. When this mixture is cautiously added to an alcohol dissolved in acetone, it enables the isolation of oxidation products like carbonyl compounds and carboxylic acids in high yields, a process known as the Jones Oxidation.
Attention: Chromium (VI) compounds are toxic and must be handled with care.
Recent Literature
At a low temperature of -78 °C, CrO3 catalyzed by periodic acid effectively oxidized benzyl alcohols and benzyl TBDMS ethers into their respective carbonyl compounds, achieving high yields. This oxidation process demonstrated remarkable functional group tolerance and a pronounced selectivity towards the TBDMS group over the TBDPS group.
S. Zhang, L. Xu, M. L. Trudell, Synthesis, 2005, 1757-1760.
https://doi.org/10.1055/s-2005-869975
At a low temperature of -78 °C, CrO3 catalyzed by periodic acid effectively oxidized benzyl alcohols and benzyl TBDMS ethers into their respective carbonyl compounds, achieving high yields. This oxidation process demonstrated remarkable functional group tolerance and a pronounced selectivity towards the TBDMS group over the TBDPS group.
S. Zhang, L. Xu, M. L. Trudell, Synthesis, 2005, 1757-1760.
https://doi.org/10.1055/s-2005-869975
CrO3 proves to be a potent catalyst in facilitating benzylic oxidation reactions when partnered with periodic acid as the terminal oxidant, with acetonitrile serving as the solvent. This system enables the oxidation of substituted electron-deficient toluenes and diarylmethanes, resulting in the formation of their respective substituted benzoic acids and ketones with exceptional yields. Furthermore, benzyl ethers, including isochroman and phthalan, undergo complete conversion into 3,4-dihydroisocoumarin and phthalide, respectively, with quantitative yields.
S. Yamazaki, Org. Lett., 1999, 1, 2129-2132.
https://doi.org/10.1021/ol991175k
A sequential reaction sequence involving a PdCl2/CrO3-catalyzed Wacker process, followed by an acid-catalyzed dehydration, allows for the efficient synthesis of β-substituted and β,β-disubstituted α,β-unsaturated methyl ketones from homoallyl alcohols featuring a terminal double bond. However, when the same protocol is applied to internal homoallyl alcohols, it leads to the regioselective formation of nonconjugated unsaturated carbonyl compounds.
V. Bethi, R. A. Fernandes, J. Org. Chem., 2016, 81, 8577-8584.
https://doi.org/10.1021/acs.joc.6b01899
The oxidation of primary alcohols to carboxylic acids, catalyzed by CrO3 in the presence of H5IO6 as a co-oxidant, proceeds efficiently with a minimal amount of CrO3 (1-2 mol%) and requires 2.5 equivalents of H5IO6 in a wet acetonitrile (MeCN) medium. This reaction yields carboxylic acids in excellent purity, demonstrating its high efficacy. Notably, for alcohols possessing adjacent chiral centers, the oxidation process does not significantly impact their stereochemical configuration, indicating minimal racemization occurs. Furthermore, secondary alcohols undergo clean oxidation to form ketones, highlighting the versatility of this CrO3-catalyzed system in differentiating between primary and secondary alcohols.
M. Zhao, J. Li, Z. Song, R. Desmond, D. M. Tschaen, E. J. J. Grabowski, P. J. Reider, Tetrahedron Lett., 1998, 39, 5323-5326.
https://doi.org/10.1016/S0040-4039(98)00987-3
Trihaloacetic acids can be efficiently converted into trichloromethyl and tribromomethyl ketones through a catalyzed reaction with aldehydes, which is subsequently followed by oxidation. The formation of trichloromethyl ketones specifically occurs through the coupling of organozinc intermediates with trichloroacetyl chloride.
E. J. Corey, J. O. Link, Y. Shao, Tetrahedron Lett., 1992, 33, 3435-3438.
https://doi.org/10.1016/S0040-4039(00)92656-X
Chromium trioxide (CrO3) serves as an effective catalyst for the oxidation of benzylic compounds in the presence of periodic acid as the oxidizing agent, utilizing acetonitrile as the solvent. This process efficiently converts substituted electron-deficient toluenes and diarylmethanes into their corresponding benzoic acids and ketones, respectively, in high yields. Additionally, benzyl ethers, including isochroman and phthalan, undergo transformation into 3,4-dihydroisocoumarin and phthalide, respectively, with quantitative yields.
S. Yamazaki, Org. Lett., 1999, 1, 2129-2132.
https://doi.org/10.1021/ol991175k
The use of triphenylphosphine as a promoter facilitates an efficient one-pot synthesis of polysubstituted 2,5-dihydropyrrole derivatives through the reaction between dialkyl acetylenedicarboxylates and β-aminoketones. Subsequently, the obtained 2,5-dihydropyrroles can be readily oxidized to their corresponding pyrrole derivatives utilizing chromium trioxide as the oxidant.
M. Anary-Abbasinejad, E. Poorhassan, A. Hassanabadi, Synlett, 2009, 1929-1932.
https://doi.org/10.1055/s-0029-1217516
Quoted
from:https://www.organic-chemistry.org/chemicals/oxidations/chromium-trioxide.shtm
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