3-Formylchromone to Quinoline Interconversion

Significance

On the basis of previous work concerned with the interconversion of 3-formylchromones to pyridine (S. V. Ryabukhin et al. Heterocycles 2008, 75, 583), a facile method for the synthesis of 3-(2-hydroxybenzoyl)quinolines and 7H-chromeno[3,2-c]quinolin-7-ones is reported. The reaction involves a TMSCl-mediated Michael addition-ring opening-recyclization of 3-formylchromone induced by aniline derivatives. Depending on the starting anilines, two different quinoline products (A and B) are formed. To account for these observations, a viable mechanism was proposed based on anilines acting either as N- or C-nucleophiles. As evidence, LCMS analysis detected one of the byproducts from the mechanistic pathway. Yields range from modest to good and the substrate scope was very well studied.