Oxidation Jones reagent

JAPP Oxazole synthesis 187 JAPP KLINGEMANN Hydrazone synthesis 188 JAROUSSE MAKOSZA Phase transler 189 JEGERTetrahyikoturan synthesis 190 JOHNSON Phenol aHcynylation 191 Johnson 168,197,240 JONES Oxidation reagent 192 JULIA BRUYLANTS Cyclopropyl earbinol rearrangement 193... 

This preparation illustrates a general and convenient way of oxidizing secondary alcohols to ketones in high deld. This procedure, usually called the Jones oxidation or oxidation by use of the Jones reagent, offers the advantage of almost instantaneous... 

Any oxidizing reagents, including H2Cr04, Jones reagent or PCC, can be used to oxidize 2° alcohols to ketones. However, the most common reagent used for oxidation of 2° alcohols is chromic acid (H2Cr04). 

Any aqueous oxidizing reagent, e.g. chromic acid (CrOs in aqueous acid), Jones reagent (CrOs in acetone) and KMn04 in basic solution, can oxidize aldehydes to carboxylic acids. 

All of the usual chromium-based oxidation reagents that have been used for the oxidation of cyclobutanols to cyclobutanones, for example, chromium(VI) oxide (Jones reagent),302 pyri-dinium chlorochromate,304 pyridinium dichromate,307 and chromium(YI) oxide/pyridine (Collins),303 are reported to do so without any serious problems. Alternatively, tetrapropylam-monium perruthenate in the presence of A-methylmorpholine A -oxide. oxalyl chloride in the presence of triethylamine in dimethyl sulfoxide (Swern),158,309,310 or phenyl dichlorophos-phate in the presence of triethylamine and dimethyl sulfoxide in dichloromethane (Pfitzner-Moffatt),308 can be used. The Pfitzner-Moffatt oxidation procedure is found to be more convenient than the Swern oxidation procedure, especially with respect to the strict temperature control that is necessary to achieve good yields in the latter, e.g. oxidation of 1 to give 2.308... 

These authors also described a three-step synthesis of 13Z-retinoic acid [56], The obtained hydroxydihydropyrane (66%) was oxidized either by Jones s reagent (CrC>3, water, H2SO4, 90%) or Corey s reagent (pyridinium chlorochromate (PCC), 65%). Finally, the dihydropyranone was transformed into retinoic acid (as a mixture of 9E, 13Z, and 9Z,13Z), by /BuOK, according to a known procedure [57], Fig. (26). 

Interestingly, in Jones oxidation, chromic acid is almost always generated from chromium trioxide while in the rest of the chromic acid oxidations, sodium or potassium dichromate are almost exclusively used. This seems to be the result of an irrational tradition originated since the reagents... 

During the oxidation, an acid-catalyzed cyclization of the product by attack of the nitrogen atoms on the ketone, leading to three different aminals, must be avoided. A Parikh-Doering oxidation gives a good yield of the desired ketone, while PCC, Dess-Martin reagent and Jones oxidation deliver diverse amounts of aminals. 

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