A combination of tandem amine-exchange/heterocyclization and biaryl coupling reactions for the straightforward preparation of phenanthro[9,10-d]pyrazoles.
The tandem amine-exchange/heterocyclization of enaminoketones is successfully applied to the regioselective preparation of a series of new 4,5-diarylpyrazoles by reaction of phenylhydrazine and several 3-N,N-(dimethylamino)-1,2-diarylpropenones. The comparison of a vast array of biaryl coupling procedures provides general, complementary approaches to new phenanthro[9,10-d]pyrazoles. The most efficient procedures for this final step in the construction of the tetracyclic system are based on a Stille-type tandem stannylation-biaryl coupling of o,o'-dihalogenated diarylpyrazoles and an hypervalent iodine-mediated nonphenolic oxidative coupling of nonhalogenated precursors.
Olivera
R
R
Kimika Organikoa Saila, Zientzi Fakultatea, Euskal Herriko Unibertsitatea, P.O. Box 644, 48080 Bilbao, Spain.
SanMartin
R
R
Domínguez
E
E
D003500:Cyclization; D007202:Indicators and Reagents; D007364:Intercalating Agents / Q000138:chemical synthesis*; D010084:Oxidation-Reduction; D011720:Pyrazoles / Q000138:chemical synthesis*
D007202:Indicators and Reagents; D007364:Intercalating Agents; D011720:Pyrazoles