1,6-Conjugated Addition-Mediated [2+1] Annulation: Approach to Spiro[2.5]octa-4,7-dien-6-one

A formal 1,6-conjugated addition-mediated [2+1] annulation to synthesize spiro[2.5]­octa-4,7-dien-6-one with <i>p</i>-quinone methides and sulfur ylides has been described. This domino-type process was highly diastereoselective and exhibited good functional group tolerance and scalability without the use of metals and bases.