Abstract: A process for the preparation of 4-tert-butyl-N-[6-(2-hydroxy-ethoxy)-5-(2-methoxy-phenoxy)-[2,2?]bipyrimidinyl-4-yl]-benzenesulfonamide, bosentan, comprising the reaction of a compound of formula (II) or a salt thereof, wherein Z is an optionally protected hydroxy group, with a compound of formula (III), in the presence of a base; and, if necessary, the removal of the hydroxy-protecting group, and/or, if desired, the conversion of a compound of formula (I) to a salt thereof, or vice versa; and novel intermediates useful for its synthesis.