The present invention relates to a process for preparation of amino substituted benzothiazole derivatives of formula I ##STR00001## wherein R.sup.1, R.sup.2 and R.sup.3 are independently from each other hydrogen, lower alkyl, lower alkoxy or halogen; R.sup.4 is hydrogen, lower alkyl, lower alkyloxy, halogen, or is a five or six membered non aromatic heterocyclyl group, unsubstituted or substituted by lower alkyl or an oxo-group, or is --NR.sup.5R.sup.6, wherein R.sup.5 and R.sup.5 are independently from each other hydrogen, lower alkyl, --C(O)-lower alkyl, --(CH.sub.2).sub.nO-lower alkyl or benzyl, opionally substituted by lower alkyl, or is an five or six membered heteroaryl group; R.sup.1 and R.sup.2 or R.sup.2 and R.sup.3 may form together with the corresponding carbon atoms a ring containing --O--CH.sub.2--O-- or --CH.dbd.CH--CH.dbd.CH--; R is hydrogen or --C(O)R'; R' is a five or six membered non aromatic heterocyclyl group, five or six membered heteroaryl group or is aryl, which rings may be substituted by the groups, selected from lower alkyl, halogen-lower alkyl, lower alkoxy, cyano, nitro, --C(O)H, --C(O)OH or by pyrrolidin-1-yl-methyl; n is 1 to 4; or a pharmaceutically acceptable salt thereof, wherein the cyclization is carried out by the treatment of a compound of formula ##STR00002## with sulphoxide/HBr/solvent to give the desired products of formula I for R is hydrogen (formula IA) or for R is --C(O)R' (formula IB) ##STR00003##