Studies on solid state photoreaction of acetylcoumarin and its derivatives with indole

The photochemical reaction of 3-acetylcoumarin and its 7-acetyloxy, 7-benzoyloxy, 6-bromo.and 5,6-benzo derivatives with indole in solid state gave only condensation products, while 3-acetyl-6-nitrocoumarin with indole gave ring-cleavage decarbonyl addition product in the solid state. 3-Acetylcoumarin and its derivatives with indole can not undergo photochemical reaction in solution. The solid-state photochemical reaction shows a high selectivity. The effect of the nature of substituent and the position of substitution were also investigated, the withdrawing substituent facilitate the photoreaction and there is a higher reactivity of acetyl at position 3 than at position 6 and 8. The structures of six new products were identified by IR, MS, ¹H NMR and elemental analysis.