On the chemistry of stable alpha-oxoketenes

This short review describes the preparation and chemistry of sterically stabilized alpha -oxoketenes, which can be isolated and handled as true neat compounds. Their reactions with dienophiles afford [4+2] - as well as [2+2] cycloadducts depending on their ability to adopt that conformation suitable for each type of cycloaddition reactions. Addition of nucleophiles leads either to dipivaloylacetic acid derivatives as expected products or to the rare molecular skeleton of mono- or bifunctionalized bridged bisdioxines, which exhibit axial chirality. The bifunctionalized derivatives may serve as novel spacer units in several macrocyclic systems.