D1 Antagonists have been reported to be potentially useful in a number of therapeutic areas. Sch-39166 is an example of such a selective D1 antagonist. Three different routes based on (1S,2S)-1-phenyl-1,3-propanediol (19), (+)-L-homophenylalanine (27) or trans-(+)-(1R,2R)-2-hydroxy-1-(methylamino)-1,2,3,4-tetrahydronaphthalene (37) were developed for the commercial preparation of Sch-39166. After analyzing each route for the best combination of cost, yield, throughput and efficiency, the synthesis of Sch-39166 starting from 37, which involves the opening of an aziridinium, was selected for optimization into the commercial route.