On heating with trichloroacetic acid or trifluoroacetic acid, 2, 4-dimethoxyphenethyl methylsulfinylmethyl ketone (1) cyclized to 2, 3-dimethoxy-5-methylthio-6-oxo-5, 6, 7, 8- tetrahydronaphthalene (2) through an intramolecular nucleophilic substitution of a sulfonium ion intermediate (20b), while a β-ketosulfoxide having naphthalene nucleus (3) cyclized to a tetrahydrophenanthrene 4via a Pummerer rearrangement product 23. Treatment of 1 with ...
