One-Pot (3 + 2) Cycloaddition–Isomerization–Oxidation of 2,2,2-Trifluorodiazoethane and Styryl Derivatives

Abstract

A facile access to 5-aryl-3-trifluoromethylpyrazoles has been developed by a one-pot (3 + 2) cycloaddition–isomerization–oxidation sequence employing 2,2,2-trifluorodiazoethane and styryl derivatives. A broad variety of functional groups and good yields are achieved under mild conditions. Additionally, the functionalization of 3-trifluoromethylpyrazoles was studied. DFT calculations of the cycloaddition transition state energies are consistent with the experimentally observed reactivity.

Iodobenzene-Catalyzed Synthesis of Fully Functionalized NH-Pyrazoles and Isoxazoles from α,β-Unsaturated Hydrazones and Oximes via 1,2-Aryl Shift

“…The groups of Zhu and Tanimori accessed pyrazoles (suitable for 4-Me/H only) and indazole, respectively, from hydrazones through C–H amination in the presence of I­(III) reagents (Scheme a) . Very recently, Carreras and co-workers reported PIDA-mediated synthesis of 5-aryl-3-CF 3 -pyrazoles (disubstituted products) from trifluorodiazoethane and styrynes . Iodine­(III) reagents have also been used for the preparation of 4-unsubstituted or 4,5-carbocycle-fused isoxazoles from ynes/enes and oximes via in situ generated nitrile oxides (Scheme b) .…”