Abstract The Friedel-Crafts acylation of anisole with acetic anhydride using ytterbium (III) tri [tris (nonafluorobutanesulfonyl) methide] was studied with respect to catalyst loading. A strong inhibitory effect due to the product became apparent from doping experiments and from examination of the kinetic data. This understanding allowed catalyst loadings to be reduced to as little as 0.1 mol% for effective acylation under a suitable temperature and ...