Oxidation of Benzylic Alcohols with Urea Hydrogen Peroxide/Calcium Chloride in PEGDME₂₅₀

Experimental

All the alcohols and PEGDME250 were purchased from Aldrich and used as received. The reactions were checked by TLC using silica gel plates. Merck silica gel 60 (230-400 mesh) was used for flash column chromatography. 1H NMRspectra were measured by the Varian Gemini 2000 (300MHz) spectrometer tetramethylsilane as an internal standard and CDCl3 as a solvent. Mass spectra were recorded with a Micromass Autospectrometer. All products were known and identified by comparison of their 1H NMR spectra with those of reported literature data.

General Procedure. A mixture of benzylic alcohol (1.0 mmol), urea hydrogen peroxide (1.5 mmol) and calcium chloride (0.5 mmol) was stirred in PEGDME250 (2 mL) at 70 oC for 4 h. After cooling the mixture to room temperature the product is extracted into diethyl ether (3 × 20 mL), washed with water and dried over MgSO4. The combined ether extracts were concentrated under reduced pressure and the crude product was purified by flash column chromatography (ethyl acetate/n-hexane = 1:3, v/v) to give the desired carbonyl compound.