Pinacol Cross-Coupling Promoted by an Aluminyl Anion

A simple sequential addition protocol for the reductive coupling of ketones and aldehydes by a potassium aluminyl grants access to unsymmetrical pinacolate derivatives. Isolation of an aluminium ketyl complex presents evidence for the accessibility of radical species. Product release from the aluminium centre was achieved using an iodosilane, forming the disilylated 1,2-diol and a neutral aluminium iodide, thereby demonstrating the steps required to generate a closed synthetic cycle for pinacol (cross) coupling at an aluminyl anion. The potassium aluminyl K[Al(NON)] (NON=[O(SiMe2NDipp)2]2-) is a suitable platform for the pinacol coupling of aldehydes and ketones. Isolating an intermediate allows unsymmetrical examples to be accessed via a sequential addition strategy. A rare example of a p-block ketyl complex was isolated, and DFT was used to confirm a carbon-based radical. Product release was achieved using an iodosilane, demonstrating the steps required to generate a closed synthetic cycle.image