A three-component one-pot condensation of 2-[2-(4-chlorophenyl)-2-oxoethyl)]isoquinolinium bromide with benzo[1,3]dioxol-5-ol and an arylglyoxal in the presence of catalytic amounts of 1,4-diaza-bicyclo[2.2.2]octane in refluxing water gave a series of seven trans-(4-chlorophenyl)-7-aryl-6,7-dihydro[1,3]dioxolo[4,5- f][1]benzofuran-6-yl)methanones in excellent yield and in a short time.