Divergent Cascade Ring Expansion Reactions of Acryloyl Imides

Macrocyclic and medium-sized ring ketones, lactones and lactams can all be made from common acryloyl imide starting materials via divergent, one-pot cascade ring expansion reactions. Following either conjugate addition with an amine or nitromethane, or osmium(VIII) catalysed dihydoxylation, rearrangement via a 4-atom ring expansion takes place spontaneously to form the ring expanded products. A second ring expansion can also be performed following a second iteration of imide formation and alkene functionalisation/ring expansion. In the dihydroxylation series, 3- or 4-atom ring expansion can be performed selectively, depending on whether the reaction is under kinetic or thermodynamic control.