Revisiting the Ullmann−Ether Reaction: A Concise and Amenable Synthesis of Novel Dibenzoxepino[4,5-<i>d</i>]pyrazoles by Intramolecular Etheration of 4,5-(<i>o,o</i>‘-Halohydroxy)arylpyrazoles
approach based on the palladium-catalyzed biaryl-ether linkage formation (Buchwald-Hartwig reaction) was also successfully applied, offering limitations with regard to the steric demand of the substituents. The synthesis of the key o,o'-halohydroxy-4,5-diarylpyrazole intermediates proceeds through the construction of the heterocyclic ring by a tandem amine-exchange/heterocyclization sequence of 3-N,N-(dimethylamino)-1