Synthesis dibenzo pyranones

The palladium catalyzed benzannulation reaction, described by Yamamoto, was successfully extended to the synthesis of condensed pyranone derivatives. The precursor to the cyclization underwent the benzannulation spontaneously under the applied Sonogashira coupling conditions (8.40.) on formation, to give the desired dibenzo />,ri pyranone. The functionalities tolerated in the process include unsaturated bonds and polar functional groups, such as hydroxyl.52... 

A one-pot synthesis of dibenzo[f>,d]pyranones from the aryl propenoate 17 proceeds via sequential Sonogashira coupling and an intramolecular benzannulation. <02JOC5138>. 

Remote metalation of biaryls and m-teraryls provides a general synthesis of substituted and condensed fluorenones (eq47). Similarly, biaryl 0-carbamates undergo remote metalation and anionic Fries rearrangement to 2-hydroxy-2 -carboxamidobiaryls, which are efficiently transformed into dibenzo[fc,i/]pyranones. ... 

Wang, W. (1991) Directed ortho and remote aromatic metalation synthesis of highly substituted biaryls, dibenzo(b,d)pyranones and 3,3 -substituted-l,l -bi-2-naphthols. M.Sc. Thesis. University of Waterloo, Canada. 

---