Enantioselective aromatic Claisen rearrangement of allyl 2-naphthyl ethers catalyzed by -Cu(ii) complexes

The first catalytic enantioselective aromatic Claisen rearrangement of allyl 2-naphthyl ethers using 5-10 mol% of pi-copper(ii) complexes is reported. A Cu(OTf)(2) complex with an l-alpha-homoalanine amide ligand gave (S)-products in up to 92% ee. Conversely, a Cu(OSO2C4F9)(2) complex with an l-tert-leucine amide ligand gave (R)-products in up to 76% ee. Density-functional-theory (DFT) calculations suggest that these Claisen rearrangements proceed stepwise via tight-ion-pair intermediates, and that (S)- and (R)-products are enantioselectively obtained via the staggered transition states for the cleavage of the C-O bond, which is the rate-determining step.