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Pure Appl. Chem., 2008, Vol. 80, No. 5, pp. 967-977

Enantio- and regioselective CpRu-catalyzed Carroll rearrangement

Martina Austeri, Frederic Buron, Samuel Constant, Jerome Lacour, David Linder, Jessica Müller and Simone Tortoioli

Department of Organic Chemistry, University of Geneva, quai Ernest Ansermet 30, CH-1211 Geneva 4, Switzerland

Abstract: The addition of unstabilized carbonyl nucleophiles to allyl-metal fragments still represents a challenge for generating stereoselectively tertiary (and quaternary) stereogenic centers. In this context, the decarboxylative Carroll rearrangement of secondary and tertiary allyl β-ketoesters is particularly interesting since chiral γ,δ-unsaturated ketones are obtained. Herein, we show that CpRu half-sandwich complexes can, in the presence of selected enantiopure diimine ligands, catalyze this transformation and afford complete conversions and decent level of enantiomeric excess. Zwitterionic adducts of a hexacoordinated phosphorus anion and CpRu moieties were also associated and shown to generate air-, moisture-, and microwave-stable catalysts that can be readily purified and recycled. Carroll rearrangements of allylic β-ketoesters performed with these zwitterionic species occur with better regio- and enantioselectivity.