Diels-Alder routes to angularly halogenated cis-fused bicyclic ketones: Readily accessible cyclynone intermediates.

We have developed an efficient Lewis acid-catalyzed Diels-Alder route to a series of cis-fused bicyclic ketones bearing quaternary halogenation at the angular position. We have also developed a Diels-Alder based one-flask method for the regioselective preparation of TBS-protected 6-hydroxy tetralone and 5-hydroxy indanone derivatives.