Synthesis of Spiro[4.5]trienones by Intramolecular ipso-Halocyclization of 4-(p-Methoxyaryl)-1-alkynes

A wide variety of 3-halospiro[4.5]trienones are readily prepared in good to excellent yields by the intramolecular ipso-halocyclization of 4-(p-methoxyaryl)-1-alkynes under mild reaction conditions. ICl, I₂, and Br₂ are all effective electrophiles for this process under carefully optimized reaction conditions.