Heterocyclic [c]‐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 [c]‐fused coumarins, e. g. isoxazoles, pyrazoles and 1,5‐diazepines, under mild conditions. In these reactions, 2a–d are – despite of their thermolability — superior to the corresponding 4‐chloro‐3‐coumarincarbaldehydes 1a–d, from which they were prepared. An improved method for the preparation of 1a–d from 4‐hydroxy‐coumarins is described.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.