Lewis Acid Catalyzed Tandem Polycyclization of Internal Alkynols and Vinyl Azides

A novel Lewis acid catalyzed tandem cyclization reaction of internal alkynols and vinyl azides has been achieved to afford a series of products containing a pyran-based indeno­[1,2-c]­isochromene scaffold in moderate to high yields. This tandem polycyclization protocol provides a straightforward entry to construct the complex polycyclic skeleton through cycloisomerization, formal [4 + 2] cycloaddition, and an elimination process.