The invention discloses a method for preparing (S)-1-(4-methoxy benzyl)-1, 2, 3, 4, 5, 6, 7, 8-octahydro
isoquinoline which is a
dextromethorphan intermediate. The method includes selectively hydrogenating 1-(4-methoxy benzyl)-3, 4, 5, 6, 7, 8-octahydro
isoquinoline (II) under the condition of (R)-N-(5-
fluorine-2-hydroxyl benzyl)-2-methylpropane-2-
sulfinamide and
trichlorosilane to obtain the (S)-1-(4-methoxy benzyl)-1, 2, 3, 4, 5, 6, 7, 8-octahydro
isoquinoline (I). The 1-(4-methoxy benzyl)-3, 4, 5, 6, 7, 8-octahydro isoquinoline (II) is used as a
raw material, and the (R)-N-(5-
fluorine-2-hydroxyl benzyl)-2-methylpropane-2-
sulfinamide is used as an organic
chiral ligand. The method has the advantages that the organic
chiral ligand is used, and the
raw material is inexpensive, safe, simpleand easily available; the reaction temperatures range from -20 DEG C to -15 DEG C, and accordingly the method can be implemented in industrial production; an ee (
enantiomeric excess) value of the (S)-1-(4-methoxy benzyl)-1, 2, 3, 4, 5, 6, 7, 8-octahydro isoquinoline which is a product can reach 63%.