Thallium trinitrate-mediated ring contraction of 1,2-dihydronaphthalenes: The effect of electron-donating and electron withdrawing groups

Abstract

The oxidation of a series of 1,2-dihydronaphthalenes substituted in the aromatic ring was investigated with thallium trinitrate (TTN) in methanol or in trimethylorthoformate (TMOF) as solvent. In all cases, indans are produced, although the yield varied from excellent to poor, depending on the structure of the substrate. The presence of an electron-donating group in the substrate favors the rearrangement, whereas significant amounts of glycolic derivatives, as well as naphthalenes, were obtained in the oxidation of 1,2- dihydronaphthalenes bearing electron-withdrawing groups, such as Br and NO 2. Mechanisms for the formation of each of these products are proposed. ©2005 Sociedade Brasileira de Química.