Regiodivergent 1,2-rearrangement of alpha-siloxy aldehydes bearing alpha-aryl and alpha-alkyl substituents into alpha-siloxy ketones has been realized by using different Al Lewis acid catalyst/solvent systems. The scope of this unprecedented protocol has been investigated with various substrates, clearly demonstrating its utility for the selective synthesis of two structural isomers from one substrate. Controlled experiments proved that the regiodivergency resulted from the switch of the migrating group. (C) 2009 Elsevier Ltd. All rights reserved.