A catalyst-free synthetic approach is described for the synthesis of 4-quinolone derivatives through a tandem amination/conjugated Michael addition sequence of 1-(2-fluorophenyl)prop-2-yn-1-one derivatives. The [5+1]-cyclization proceeds efficiently at a high temperature under an inert atmosphere with lithium carbonate as a base, and it provides a practical route to a diverse range of 4-quinolones. The mechanism was studied in details and several of the intermediates were isolated.
Key words
quinones - ketones - domino reactions - aminations - Michael additions - heterocycles