Aromatic sulphonation. Part 73. Behaviour of three 9-alkylanthracenes containing one side-chain α-hydrogen in dioxan–SO3 complex in dioxan as sulphonating medium

Abstract

The reactions of 9-isopropyl-, 9-s-butyl-, and 9-cyclohexyl-anthracene with dioxan–SO₃ in dioxan at 17 °C lead to three types of products, viz. 9-alkenylanthracenes (2), unsaturated sulphonic acids (3), and seven-membered ring sultones (4). The 9-alkenylanthracenes (2) result from a redox reaction between the 9-alkylanthracenes and SO₃ and the unsaturated sulphonic acids (3) from the subsequent sulphonation of (2). The seven-membered ring sultones are formed from the σ-complex (resulting from addition of SO₃ to the 10-position of the original substrate) by a 1,2-hydride shift from the side-chain C-α to C-9.