Friedel-Crafts 3-(2-Bromobenzoylation) of Indoles and Intramolecular Direct Arylation: An Efficient Route to Indenoindolones

An efficient two-step approach, comprising the Friedel-Crafts reaction of 2-bromobenzoyl chlorides with indoles to give 3-(2-bromobenzoyl) indoles and their palladium-catalyzed intramolecular direct arylation to give indenoindolones, has been developed. 3-(2-Bromobenzoyl) indoles were crucial intermediates; the method was successful with N-unprotected or N-protected indoles. This approach affords a convenient preparation of diverse substituted and functionalized indenoindolones in good to high yields from easily accessible starting materials. Several moieties, which are commonly integrated into bioactive compounds, can be incorporated with ease by this synthesis.