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 4 via a Pummerer rearrangement product 23. Treatment of 1 with p-toluenesulfonic acid gave a mixture of 2,3,6-trisubstituted naphthalenes (7–10), whose composition was dependent on the reaction conditions
Pteridines. I. .beta.-Ketosulfoxides and .alpha.-ketoaldehyde hemithioacetals as pteridine precursors. New selective synthesis of 6- and 7-substituted pteridines