novel efficient tandem reaction of hydrazones and α-bromo ketones is reported for the preparation of 1,3,5-trisubstituted pyrazoles by visible light catalysis. In this system, the monosubstituted hydrazones show wonderful reaction activity with alkyl radicals, generated from α-bromo ketones. A radical addition followed by intramolecular cyclization affords the important pyrazole skeleton in good to
Transition-Metal-Free<i>N</i>-Arylation of Pyrazoles with Diaryliodonium Salts
作者:Zsombor Gonda、Zoltán Novák
DOI:10.1002/chem.201502995
日期:2015.11.16
developed for the N‐arylation of pyrazoles using diaryliodoniumsalts. The transformation does not require any transition‐metal catalyst and provides the desired N‐arylpyrazoles rapidly under mild reaction condition in the presence of aqueous ammonia solution as a mild base without the use of inert atmosphere. The chemoselectivity of unsymmetric diaryliodoniumsalts was also explored with large number
A copper-catalyzed efficient method for the synthesis of a diverse variety of substituted N-aryl pyrazoles from readily available α,β-alkynic N-tosyl hydrazones and diaryliodonium triflates is realized. This one-pot multi-step methodology features a broad scope with good yields, scalability, and appreciable functional group tolerance. Detailed control experiments reveal that the reaction proceeds through