Angewandte Chemie International Edition
© WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Cover Picture (Angew. Chem. Int. Ed. Engl. 23/1997)
The cover picture shows schematically the catalytic formation of single enantiomers of 3-alkylcyclohexanones starting from cyclohexenones and the appropriate substituted alkenes. The alkenes are initially transformed into organozinc reagents that then add to the enone in a completely stereocontrolled, copper-catalyzed reaction. In the inner circle is a molecular model of a novel phosphoramidite that has been used as chiral ligand (the copper ion is indicated by a dotted sphere) in this 1,4-addition. Since several functionalized organozinc reagents are readily accessible from alkenes, this reaction and also the combined 1,4-addition/aldol reaction provide access to a variety of highly enantiomerically pure cyclohexanones. More about this method, which is also applicable to dienones, is reported by B. L. Feringa et al. on page 2620 ff. The authors thank Dr. J. Esch for the design of this picture.