1836-47-1Relevant academic research and scientific papers
Revisiting the Ullmann-ether reaction: A concise and amenable synthesis of novel dibenzoxepino[4,5-d]pyrazoles by intramolecular etheration of 4,5-(o,o′-halohydroxy)arylpyrazoles
Olivera, Roberto,SanMartin, Raul,Churruca, Fatima,Dominguez, Esther
, p. 7215 - 7225 (2007/10/03)
A concise synthesis of a series of novel dibenzoxepino[4,5-d]pyrazoles was accomplished by implementation of an intramolecular Ullmann-ether reaction on o,o'-halohydroxy-4,5-diarylpyrazoles mediated by CuBr·DMS. An alternative useful approach based on the palladium-catalyzed biarylether 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)-1,2-diarylpropenones with phenylhydrazine followed by basic hydrolysis for deprotection. The enamino ketone precursors were conveniently prepared from the corresponding O-sulfonyloxy and O-benzoyloxy ortho-substituted 1,2-diarylethanones, starting from inexpensive salicylaldehyde or phenylacetic derivatives. Preliminary binding affinity experiments against peripheral and central nervous system receptors have been done with negative results.
