Synthesis of functionalised β-keto amides by aminoacylation/domino fragmentation of β-enamino amides

Synthetic approach to 2-alkyl-4-quinolones and 2-alkyl-4-quinolone-3-carboxamides based on common β-keto amide precursors

β-Keto amides were used as convenient precursors to both 2-alkyl-4-quinolones and 2-alkyl-4-quinolone-3-carboxamides. The utility of this approach is demonstrated with the synthesis of fourteen novel and four known quinolone derivatives, including natural products of microbial origin such as HHQ and its C5-congener. Two compounds with high activity against S. aureus have been identified among the newly obtained quinolones, with MICs ≤ 3.12 and ≤ 6.25 µg/mL, respectively.

3-Carbamoylmethyl-Indole-1-Carboxylic Acid Ethyl Ester

3-Carbamoylmethyl-Indole-1-Carboxylic Acid Ethyl Ester (an ethoxycarbonyl derivative of indole-3-acetamide) is obtained by Friedel–Crafts type cyclocondensation of γ-functionalized acetoacetamide in neat polyphosphoric acid.

4-Aminoalkyl Quinolin-2-one Derivatives via Knorr Cyclisation of ω-Amino-β-Keto Anilides

In a high-yielding and solvent-free procedure N-ethoxycarbonyl protected ω-amino-β-keto anilides undergo Knorr cyclisation in neat polyphosphoric acid to provide straightforward route to 4-aminoalkyl quinolin-2-one derivatives with variable length of the alkyl chain.