An Acid Promoted, Domino Approach for the Selective Synthesis of Spirocyclic Systems^#

Design and development of an acid-catalyzed domino strategy for the rapid and selective generation of spiro-polycyclic systems from propargylic alcohols is reported. Isolation of the intermediate olefins and the control experiments suggested and supported the proposed mechanism. The key features of this strategy are the selective access to spiro-polycyclic systems, broad substrate scope (yields ranging between 50–95%), high atom economy, and operationally simple reaction procedure. We have extended this approach for the synthesis of spiro-tetracyclic and spiro-pentacyclic frameworks of dalesconols, and chamaecydin natural products respectively. (Figure presented.).