Studies on dioxirane chemoselectivity: The oxidation of an enamino moiety present in a Fischer carbene complex

Article abstract of DOI:10.1016/S0040-4020(96)00051-8

The dimethyldioxirane (DMD) promoted oxidative decomplexation of Fischer carbene complex 1, which contains a conjugated enamino moiety, was investigted. Thus, treatment of 1 with 3 molecular equivalents of DMD afforded a 52% yield of amide 3 as unique isolable organic product. When the reaction was performed with 1 molecular equivalent of DMD the formation of the enol intermediate 15 was evidenced by its capture as the tetrafluoroboric acid salt 16. This salt was unstable and when it was exposed to air gave rise to amide 3 and to low amounts of ethyl benzoate and acetophenone. These results indicate that the presence of an enamino group conjugated to the Fischer carbene moiety inverts the chemoselectivity previously observed in the DMD promoted decomplexation of these compounds. Thus, the major pathway involves the oxidation of the enamino double bond through the formation of an enol intermediate which reacts with oxygen to give products resulting from the breakdown of the molecule.