Solvent-dependent copper-catalyzed synthesis of pyrazoles under aerobic conditions.
We present a copper-catalyzed oxidative cyclization of β,γ-unsaturated hydrazones, utilizing molecular oxygen as a stoichiometric oxidant. The methodology provides distinct classes of pyrazoles simply by changing the reaction solvent. Tris-substituted pyrazoles, having a ketone functionality at the C-5 position, were obtained as the major product in ethanol, while di-substituted pyrazoles were predominantly formed in 1,1,1,3,3,3-hexafluoro-2-propanol.
Synthetic Organic Chemistry Laboratory, RIKEN, 2-1, Wako, Saitama 351-0198, Japan. sodeoka@riken.jp and RIKEN Center for Sustainable Resource Science, RIKEN, 2-1, Wako, Saitama 351-0198, Japan.
Florian
F
Pünner
Synthetic Organic Chemistry Laboratory, RIKEN, 2-1, Wako, Saitama 351-0198, Japan. sodeoka@riken.jp and RIKEN Center for Sustainable Resource Science, RIKEN, 2-1, Wako, Saitama 351-0198, Japan.
Yoshihiro
Y
Sohtome
Synthetic Organic Chemistry Laboratory, RIKEN, 2-1, Wako, Saitama 351-0198, Japan. sodeoka@riken.jp and RIKEN Center for Sustainable Resource Science, RIKEN, 2-1, Wako, Saitama 351-0198, Japan.
Mikiko
M
Sodeoka
D002384:Catalysis; D003300:Copper / Q000737:chemistry*; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D011720:Pyrazoles / Q000138:chemical synthesis* / Q000737:chemistry; D012997:Solvents / Q000737:chemistry
D011720:Pyrazoles; D012997:Solvents; D003300:Copper; D010100:Oxygen