Alkyne insertion into Cu-Al bonds: control of regio-/stereo-chemistry and selective functionalization to form copper acyl compounds

We report on the insertion of alkynes into heterometallic M–M' bonds, producing (aluminylalkenyl)copper compounds which possess differential reactivity at the two derived M–C functions. Uniquely, this system is capable of controlling access to isolable syn or anti dimetallated alkenes, by employing either kinetic or thermodynamic control. Variation of reaction time also allows regiocontrol to be exerted over the insertion of unsymmetrical alkynes. Subsequent derivatization with CO is both stereoselective (to syn systems) and regioselective (to Cu–C bonds), leading to the formation of the first structurally characterized examples of copper acyl compounds - aided by the cooperative reactivity of the proximal aluminium centre.