Deoxygenation of Hydroquinones as a General Route to Norbornane-Fused Aromatic Systems: An Entry into Substituted and Functionalized Dimethano- and Methanoanthracenes

A high-yielding route to substituted and functionalized
dimethanoanthracenes
by the Pd-catalyzed deoxyenation of the corresponding hydroquinone
precursors is described. Attempts were made to deoxygenate the 9,10-dimesylate,
ditosylate, and ditriflate derivatives of anti-dimethanoanthracene 1a, and it was found that under the studied conditions only
the ditriflate 8a gave the corresponding deoxygenated
aromatic scaffold. Optimization of the reaction conditions identified
the Pd­(OAc)2/dppf tandem as a suitable catalytic system
for this transformation. The presented strategy was further extended
to a novel and efficient synthetic route to methanoanthracenes employing
a one-pot Pd-catalyzed deoxygenation/hydrogenation sequence.