Development of a Large-Scale Stereoselective Process for (1R,4S)-4-(3,4-Dichlorophenyl)-1,2,3,4-tetrahydronaphthalen-1-amine Hydrochloride

A convenient, multikilogram-scale, stereoselective process for the synthesis of (1R,4S)-4-(3,4-dichlorophenyl)-1,2,3,4-tetrahydronaphthalen-1-amine hydrochloride 1 is described. The key steps involve synthesis of sulfinyl imine (R_s,4S)-5 from (S)-tetralone (4S)-3 and (R)-tert-butylsulfinamide (R_s)-4, and its stereoselective reduction with 9-BBN to produce the (1R)-amine center of 1. The process has been scaled up to multikilogram scale and gives 1 in an overall yield of >50% with a chemical purity of 99.7 A% by HPLC and stereochemical purity of >99.9% by chiral HPLC.