described are compounds of the formula : ## str1 ## wherein y denotes dimethylamino , methylpropynylamino , pyrrolidino , piperidino , or morpholino ; r 1 and r 2 independently of each other denote hydrogen or loweralkyl ; and x denotes loweralkyl , loweralkoxy , or halo ; and n is and integer from 1 to 3 inclusive , or pharmaceutically acceptable salts thereof . the compounds exhibit antiarrhythmic activity without unwanted sympathomimetic effects .