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20.5.1.3.3.9 Method 9: Using Potassium Permanganate

DOI: 10.1055/sos-SD-020-00673

Yan, L.; Lin, S.; Liu, P.Science of Synthesis, (200720763.

Neutral potassium permanganate solution oxidizes cyclic acetals to the corresponding hydroxy esters at room temperature in the presence of benzyltriethylammonium chloride as a phase-transfer catalyst. Productivity is good and, for example, 2-phenyl-1,3-dioxane affords the ester 136 (n = 2) in 85% yield (Scheme 41). If the potassium permanganate solution is acidified (pH ca. 5.5) by the addition of acetic acid, then this reagent can be used to oxidize acetals to the corresponding carboxylic acids. The procedure, using neutral conditions, can be extended to the use of potassium permanganate in an organic solvent (e.g., benzene or dichloromethane) without using a phase-transfer catalyst, although in the case of the acetal 137 the yield of the hydroxy ester 138 is only 71% (Scheme 41).[‌159‌]

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