A cascade AgOTf-catalyzed chemoselective approach to 3,5/1,3-disubstitued pyrazoles from propargylic alcohols and para-tolylsulfonohydrazide has been developed. Good chemoselectivity is observed depending on the different substituents in the alkyne moiety of the propargylic alcohols, generating two different kinds of products through different aromatization mechanisms. The pyrazolo[5,1-a]isoquinoline skeleton can also be effectively constructed by this method through a cascade bicyclization process.
Copper on iron promoted one-pot synthesis of β-aminoenones and 3,5-disubstituted pyrazoles
作者:Szabolcs Kovács、Zoltán Novák
DOI:10.1016/j.tet.2013.08.047
日期:2013.10
The reaction of hydroximoyl chlorides with acetylenes in the presence of a copper on iron bimetallic system leads to beta-aminoenones via reductive ring opening of isoxazole intermediates. The valuable beta-aminoenone building blocks can be isolated or transformed into pyrazoles with the addition of hydrazine in a straightforward one-pot procedure. (C) 2013 Elsevier Ltd. All rights reserved.
Glotova, T.E.; Nakhmanovich, A.S.; Yarosh, O.G., Journal of general chemistry of the USSR, 1991, vol. 61, # 9.2, p. 1893 - 1895