ChemInform Abstract: 4-Naphthyl-Substituted Bis(oxazoline): A New, Easily Recoverable and Efficient Chiral Ligand in Asymmetric Catalysis of the Diels-Alder Reaction.

Abstract

Abstract 2, 2-Bis{2-[(4R)-(2′-naphthyl)-1, 3-oxazolinyl]}propane and its (4S) enantiomer were prepared starting from 2-vinylnaphthalene, following the Sharpless protocol, and were found to be optically pure (ee ≥ 99.5%) by hplc analysis. These new bis(oxazolines) are efficient chiral ligands in the asymmetric catalysis of the Diels-Alder reaction ofN-alkenoyl-oxazolidin-2-one derivatives since endo cycloadducts are obtained with up to 94% ee. Different Lewis acids were tested, the best one being the Mg(II) cation derived from the corresponding triflate. A remarkable feature of such new chiral ligands is the low solubility in polar solvents, so that the chiral ligand can be easily recovered by a simple filtration. The recovered ligand can be directly reused in other asymmetric syntheses, without any further purification and, overall, without any drop in the induced enantioselectivities. New chiral bis(oxazolines) were prepared starting from 2-vinylnaphthalene, and were shown to be efficient chiral ligands in the asymmetric catalysis of the Diels-Alder reaction of N-alkenoyl-oxazolidin-2-one derivatives: complexes built on magnesium triflate the endo cycloadducts to be obtained with up to 94% ee. A remarkable feature of such new chiral ligands is the low solubility in polar solvents allowing an easy recovery of the bis(oxazoline) in 75% yield by a simple filtration Download : Download full-size image .