Lewis acid-catalyzed Friedel-Crafts alkylations of 3-hydroxy-2-oxindole: an efficient approach to the core structure of azonazine.

A Lewis acid catalyzed Friedel-Crafts reaction of electron rich aromatics with 3-alkyl-3-hydroxy-2-oxindole (5) has been developed. The methodology provides a straightforward access to the core of azonazine (2) sharing an all-carbon quaternary stereocenter at the tetracyclic ring junction.