Thermal and photochemical Wallach rearrangement of azoxybenzene in zeolite cages

Acidic zeolites HY and CaY catalyse the Wallach rearrangement of azoxybenzene (I) leading mainly to the formation of para-hydroxyazobenzene (II) and ortho-hydroxyazobenzene (III). In this transformation, increasing the loading level of I results in the formation of a larger amount of para-isomer. As observed in isotropic media, photochemical Wallach rearrangement in the presence of various cation-exchanged faujasites results in the predominant formation of the ortho-isomer from the S-1 state and this rules out any appreciable heavy atom effect. (C) 2000 Elsevier Science B.V. All rights reserved.