Double bond migration Oppenauer oxidation

The modified Oppenauer oxidation was used in the synthesis of estrone by P. Kocovsiw et al. The tetracyclic did was exposed to aluminum isopropoxide and A/-methyl-piperidine-4-one (oxidizing agent) to obtain the corresponding enone in good yield. The formation of the enone involved the migration of the initial p,y-double bond. The treatment of this enone with TsOH overnight in ether led to the formation of estrone by aromatization. 

The oxidation was accompanied by migration of the double bond from the p,y to the a,p position. The resulting a,p-unsaturated compound has a characteristic absorption in the ultraviolet region of the spectrum and therefore the Oppenauer oxidation has been used as a test for localising double bonds in a variety of steroidal compounds.7 10... 

The Oppenauer oxidation has been used widely for the oxidation of steroids, particularly for the conversion of allylic secondary hydroxyl groups to a, -unsaturated ketones. p,y-Double bonds generally migrate into conjugation with the carbonyl group under the conditions of the reaction (6.46). One drawback of the method is that the rate of oxidation is rather slow and therefore the mixture is normally heated in a solvent such as toluene, although more-active catalysts that are effective at room temperature have been developed." ... 

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