Improved cyclization conditions to prepare 6-substituted pyrazolo[1,5- a ]pyridines and pyrazolo[1,5- a ]pyrazines using catalytic Ag(I) and Au(III) salts

Tandem Aza Michael Addition-Vinylogous Nitroaldol Condensation: Construction of Highly Substituted N-Fused 3-Nitropyrazolopyridines

A base-mediated tandem aza-Michael addition-vinylogous nitroaldol condensation has been described between 3,5-dialkyl 4-nitropyrazoles and alkynyl ketones/aldehydes. This transition metal-free atom economical transformation occurred via C-N and C═C bond formations in one step with the elimination of water. The construction of a variety of highly substituted N-fused 3-nitropyrazolopyridine derivatives has been demonstrated with good yields. Good to excellent regioselectivities have been achieved with unsymmetrically substituted 4-nitropyrazoles.