Studies of photoinduced addition of water and alcohols to substituted dihydroquinolines

Steady-state photolysis products of 6- and 8-substituted 2,2,4-trimethyl-1,2-dihydroquinolines in water and lower alcohols were identified by ¹H NMR. In the case of electron-donor substituents, the solvent molecule is added to the double bond of the heterocycle affording the corresponding 4-hydroxy- or 4-alkoxytetrahydroquinolines. Nitro-substituted dihydroquinolines are photostable. The addition of EtOH and PrⁿOH occurs only in the presence of water to give a mixture of alkoxy- and hydroxy-adducts. A reaction scheme is suggested.