New zeolite-catalyzed ring-closure reaction of benzilic acid

The formation of the reactive carboxydiphenylmethyl cation from benzilic ac id under Bronsted acidic conditions gives rise to a variety of compounds de pending on the reaction conditions. When applying Amberlyst-15 as the catal yst, fluorene-9-carboxylic acid is obtained together with a considerable am ount of side products. With zeolite H-Beta as the catalyst, a new intramole cular rearrangement takes place leading to 3-phenyl-1,2-dihydrobenzofuran-2 -one in high selectivity. In fact, aromatic hydroxylation takes place; acco rdingly 3-phenyl-1,2-dihydrobenzofuran-2-one can be converted into several (2-hydroxyphenyl)-benzeneacetic acid derivatives. Aromatic solvents were fo und to enter the benzilic acid rearrangement and give triphenylderivatives, of which the yields are decreasing in the expected order, namely: toluene > p-chlorotoluene > chlorobenzene > o-dichlorobenzene. (C) 2000 Elsevier Sc ience B.V. All rights reserved.