Despite its wide applicability as an oxidizing agent, chromium is not environmentally benign due to its high toxicity. Thus, the use of chromium reagents for bulk scale productions has not attained much popularity. However, methods have been developed to bypass this problem, one of them being the use of magnetic chromium(IV) oxide, which can oxidize allylic and benzylic alcohols (Scheme 4). After the reaction is completed, the CrO2 particles can be separated from the solution by a magnet.
Scheme 5
Examples:
Ref : J. Meinwald, J. Crandall, W. E. Hymans, Org. Synth. CV5 , 866.
Ref : J. R. Henry, S. M. Weinreb, J. Org. Chem. 1993 , 58 , 4145.
Ref : J. R. Henry, S. M. Weinreb, J. Org. Chem. 1993 , 58 , 4145.
Ref : M. Harmata, G. J. Bohnert, Org. Lett. 2003 , 5 , 59.