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

The first catalytic enantioselective aromatic Claisen rearrangement of allyl 2-naphthyl ethers using 5-10 mol% of π-copper(ii) complexes is reported. A Cu(OTf) 2 complex with an l-α-homoalanine amide ligand gave ( S )-products in up to 92% ee. Conversely, a Cu(OSO 2 C 4 F 9 ) 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.