Photocyclization of 2,6-dichlorodiphenylamines in solution

The reactions of diclofenac, meclofenamic acid and 2,6-dichlorodiphenylamine were studied by pulsed and steady-state photolysis. The primary photoprocess of diclofenac is ring closure, the quantum yield of cyclization in dichloromethane and aqueous solution is Φcyc = 0.03 and 0.2, respectively. The results of the two related dichlorodiphenylamines are similar in the respect that the products are the corresponding 1-chlorocarbazoles and Φcyc is small in organic solvents and largest in aqueous solution.