Microwave Enhanced Synthesis of Acridines. A New Aspect in Bernthsen Reaction.

Acridines are a well kown group of compounds [1] with a wide variety of biological properties [2]: DNA intercalating agents, anticarcinogenic, bactericidal, antimalarial, insecticides and antifungic. There are several aproaches to their synthesis. Bernthsen reaction is one of the classical methods. It is mainly the heating of diphenylamine in the presence of zinc chloride and a carboxylic acid, temperature of reaction is 200-210ºC and reaction times are several hours. But usually the yield are low. In our group we are interested in the application of microwave heating to organic synthesis [3], usually this reactions employ a domestic microwave oven and reaction vessels are just test tubes or beakers opened to the air. Bernthsen reaction seemed to be an ideal candidate to substitute conventional heating by microwave heating.