Gold(I)-catalyzed synthesis of dihydrodibenzoquinolizinium salts

A gold-catalyzed cyclization of 1-alkynyl-2-aryl tetrahydroisoquinolines is described for the synthesis of novel dihydrodibenzoquinolizinium salts. The reaction mechanism is likely to involve a 6-endo-dig cyclization and subsequent oxidation by air to give a relatively stable arylgold intermediate. This gold species undergoes protodeauration under acidic conditions to afford the title compounds. An NMR study was performed to gain further evidence and insight on the presence of the arylgold intermediate and the reaction mechanism. (Figure presented.).