Abstract
• Lewis-acid or UV light irradiation promotes rearrangement reactions. • (Naphthylmethyl)naphthols can be synthesized regioselectively. • Respective anion and radical intermediates are involved. Reaction of 1-naphthyl naphthylmethyl ethers 1 and 2 with Lewis acids (BF 3 -Et 2 O or Et 2 AlCl) in CH 2 Cl 2 produced rearranged products of the naphthylmethyl group to the 2- and 7-positions of the naphthalene, whereas rearrangement of 2-naphthyl ethers 3 and 4 proceeded to the 1-position. When benzene solutions of compound 1 was irradiated, rearrangement to the 4-positions proceeded, whereas rearrangement of 2 proceeded to the 2- and 4-position. Photoinduced rearrangement of 3 and 4 proceeded to the 1-position as in the reaction using Lewis acids. In the reaction with Lewis acids, ion pair consists of Lewis acid-coordinated naphthoxy anions and naphthylmethyl cations, and in the photoreaction, radical pair generated by homolytic cleavage of the C-O bond, are proposed to be intermediates. Calculations of the negative charge distribution and the spin density of the intermediates showed that the regioselectivity of the reactions can be explained by the charge density and spin density of each fragment, steric hindrance, and solvent cage effect. 2009 Elsevier Ltd. All rights reserved.
Published Version
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