An Improved Environmentally Friendly Approach to 4-Nitro-, 4-Sulfonyl-, and 4-Aminoquinolines and 4-Quinolones through Conjugate Addition of Nucleophiles to β-(2-Aminophenyl)-α,β-ynones

Sequential addition/annulation reactions of sulfinate and nitrite anions to beta-(2-aminophenyl)-alpha,beta-ynones led to valuable 4-sulfonylquinolines and 4-nitroquinolines. The latter proved to be versatile precursors of N-unsubstituted 4-aminoquinolines and 4-quinolones. Reaction of beta-(2-aminophenyl)-alpha,beta-ynones with DMF/NaOH resulted in the formation of 4-(dimethylamino)quinolines. The use of an alternative CO-free procedure for the preparation of substrates beta-(2-aminophenyl)-alpha,beta-ynones allowed extension of the methodology to the synthesis of 4-substituted 2-alkylquinolines.