Sulfur-Mediated ipso -Cyclization of 4-(p -Methoxyaryl)alk-1-ynes Leading to 3-Thiospiro[4.5]deca-1,6,9-trien-8-ones.

A new method for the intramolecular electrophilic ipso -cyclization of alkynes with triflic anhydride-activated sulfoxides, followed by demethylation with triethylamine in one pot, is described for the synthesis of 3-thiospiro[4.5]-decatrienones in moderate to good yields. This method provides a facile strategy for assembling the sulfur-substituted spirocyclic compounds. [ABSTRACT FROM AUTHOR]