Osmium-Centered Oxetylidene: Formation and Cleavage

Abstract

The first transition-metal–oxetylidene complex has been prepared by reaction of OsCl(η5-C5H5)(CO)(PiPr3) with 3,3-di(methoxycarbonyl)-5-hexyn-1-al and AgBF4. This novel compound is transformed into a hydroxyalkenylcarbene isomer by deprotonation and subsequent protonation of the resulting α,β-unsaturated acyl transient species. In fluorobenzene at 90 °C, the four-membered ring undergoes cycloreversion to afford a cis-dicarbonyl derivative and the cycloalkene.