Thermal and photochemical Wallach rearrangement of azoxybenzene in zeolitecages

Acidic zeolites HY and CaY catalyse the Wallach rearrangement of azoxybenze ne (I) leading mainly to the formation of para-hydroxyazobenzene (II) and o rtho-hydroxyazobenzene (III). In this transformation, increasing the loadin g level of I results in the formation of a larger amount of para-isomer. As observed in isotropic media, photochemical Wallach rearrangement in the pr esence of various cation-exchanged faujasites results in the predominant fo rmation of the ortho-isomer from the S-1 state and this rules out any appre ciable heavy atom effect. (C) 2000 Elsevier Science B.V. All rights reserve d.