Thallium trinitrate-mediated ring contraction of 1,2-dihydronaphthalenes: an approach to the synthesis of indans

Oxidation of 1,2-dihydronaphthalenes with thallium trinitrate was studied. 1,2-dihydronaphthalene, 1-methyl-1,2-dihydronaphthalene, 6- and 8-methoxy-1,2-dihydronaphthalenes gave rise to the respective ring contraction products in good yields, whereas the rearrangement was not observed using 4-methyl-1,2-dihydronaphthalene and 1-n-butyl-4-methyl-1,2-dihydronaphthalene as substrates.