A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species

Umpolung of ketone enolates by virtue of reversing natural activity, enables the development of unprecedented reactions to functionalized carbon neo-compounds. The key is the formation of electrophilic enolonium species as a discreet species. A main advantage of methods based on electrophilic enolonium species is that it obviates the need for older multiple step methods, allows the use of commercial starting materials and is simple to use.

We recently had the idea for this method when we were able to characterize the electrophilic enolonium species for the first time. Over the last year, we have developed a series of new reactions based on the two-step protocol presented here. Today, we will describe how enolonium species made in the first step can be used in in situ coupling with allyl-silanes, aromatic compounds, chloride, azide and azoles.