| 摘要 |
A process for the preparation of a compound of formula I, wherein R1 and R2 are ortho or para substituents, independently selected from the group consisting of hydrogen, hydroxyl, C1-C6 alkyl, C1-C6 alkoxy, C7-C9 aralkoxy, C2-C7 alkanoyloxy, C1-C6 alkylmercapto, halo and trifluoromethyl; R3 is hydrogen or C1-C6 alkyl ; R4 is hydrogen, C1-C6 alkyl, formyl or C2-C7 alkanoyl; n is one of the integers 0, 1, 2, 3 or 4; and the dotted line represents optional olefinic unsaturation; comprising hydrogenating a compound of formula III, in the presence of a nickel or cobalt catalyst at a temperature of about 5° C. to 25° C.
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