Abstract:
A novel cycloisomerization strategy for coumarins and quinolinones is described. Addition of ethoxyacetylide to 2-hydroxyacetophenones directly resulted in 4-substituted coumarins via 6-endo-dig-cycloisomerization of the intermediates 2-(hydroxyphenyl)-3-ethoxy-2-yn-1-ols. In the similar conditions2-aminoacetophenone produced 2-ethoxyquinoline, a masked quinolinone, which was converted to latter with an acid treatment. N-protected intermediate 8 was isolated and was converted to quinolinone (In(OTf)3 or H2SO4) and 3-iodo-2-quinolinone (I2/H+).
