STUDIES ON DIOXIRANE CHEMOSELECTIVITY - THE OXIDATION OF AN ENAMINO MOIETY PRESENT IN A FISCHER CARBENE COMPLEX

The dimethyldioxirane (DMD) promoted oxidative decomplexation of Fisch er carbene complex 1, which contains a conjugated enamino moiety, was investigated. Thus, treatment of 1 with 3 molecular equivalents of DMD afforded a 52% yield of amide 3 as unique isolable organic product. W hen 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 be nzoate and acetophenone. These results indicate that the presence of a n enamino group conjugated to the Fischer carbene moiety inverts the c hemoselectivity 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 breakdow n of the molecule.