Heterocyclic -Condensed Coumarins from 4-Azido-3-coumarincarbaldehydes
4-Azido-3-coumarincarbaldehydes 2a-d are useful starting materials for syntheses of a variety of 3,4-disubstituted coumarins as well as heterocyclic -fused coumarins, e. g. isoxazoles, pyrazoles and 1,5-diazepines, under mild conditions.In these reacti