1,3-DIPOLAR CYCLOADDITION REACTION OF CHROMONES AND COUMARIN WITH PYRIDINIUM YLIDES
1,3-Dipolar cycloaddition reaction of N-iminopyridinium ylide (2) with chromones (1) gave pyrazolopyridines (3) in moderate yields.Similarly coumarin (4) reacted with 2 to give 6H--benzopyranopyrazolopyridin-6-one (5).Furthermore chromone (1) was cyclized with pyridinium phenacylide (6) to afford 1-(2'-hydroxybenzoyl)-3-benzoylindolizine (7).