A novel tandem reaction involving an oxa-Michael addition, followed by a Friedel-Crafts alkylation has been developed. This catalytic tandem reaction, which provides facile and efficient access to optically active functionalised chromanes, proceeds under the influence of bisoxazoline-based catalysts to give diastereomerically pure products in enantioselectivities up to 81% and excellent yields. The optimisation studies, the scope of the reaction, and a model that on the basis of PM3 calculations predicts the outcome of the reaction will be detailed.

Both enantiomers of 1‐naphthylglycine were obtained in 99% ee by enzymatic resolution of the corresponding racemic amino acid amide, giving access to the novel ligands (R)‐ and (S)‐naphthylbis(oxazoline). Initial studies provided insight into the scope and limitations of the (S)‐naphthyl‐substituted bis(oxazoline) and its steric influence compared to other bis(oxazolines) in catalytic asymmetric synthesis. (© Wiley‐VCH Verlag GmbH & Co KGaA, 69451 Weinheim, Germany, 2003)

Keywords: Asymmetric catalysis / Ligand design / Bisoxazoline ligands / Non-proteinogenic amino acids / Chiral Lewis acidsThe steric influence of extended aryl substituents on 2,2Ј-bis(1,3-oxazoline) ligands was investigated in a series of asymmetric catalytic reactions such as Mukaiyama aldol and Michael reactions, hetero-Diels-Alder processes, and allylic alkylation reactions. 4,4Ј-(2-Naphthyl)-and 4,4Ј-(9-anthryl)-