PHOTOREACTIONS OF 4- AND 3-AZIDOCOUMARINS IN THE PRESENCE OF NUCLEOPHILES
The photoreactions of 4-azidocoumarins (1) and 3-azidocoumarin (2) in the presence of nucleophiles such as alcohols, thiol or amines generally gave 4-substituted 3-amino- and/or 3-substituted 4-aminocoumarins, while pyrone ring fission with incorporation of two moles of nucleophile was observed in the reaction of 1 in the presence of primary or secondary aliphatic amine as a nucleophile.Plausible mechanisms for these reactions are suggested.