合成路线1

Nitration of 4-hydroxyacetophenone with KNO3 in cold H2SO4 gave the 3-nitro derivative (II), which was protected as the benzyl ether (III) with benzyl bromide in DMF. Hydrogenation of the nitro group of (III) over PtO2 afforded aniline (IV), and further treatment of (IV) with methanesulfonyl chloride in pyridine provided sulfonamide (V). Subsequent alpha-bromination of the acetophenone (V) was achieved using CuBr2 in a refluxing mixture of EtOAc and CHCl3. Asymmetric reduction of the ketone with borane in the presence of the chiral oxazaborolidine (VII), (prepared in situ from (R)-a,a-diphenyl-2-pyrrolidinemethanol (VIII) and trimethylboroxine (IX) in boiling toluene), provided the (R)-alcohol (X). The bromo group of (X) was then substituted for a iodo group upon treatment with NaI in acetone, and the resulting (IX) was protected as the triethylsilyl ether (XII) with Et3SiCl in the presence of imidazole and dimethylaminopyridine. Reaction of 4,4'-dihydroxybenzophenone (XIII) with chlorodifluoromethane and t-BuOK yielded the bis(difluoromethyl) ether (XIV). The benzhydryl amine (XV) was then obtained by reductive amination with ammonium formate at 160 C, followed by acid hydrolysis of the intermediate formamide. Condensation of iodide (XII) with benzhydryl amine (XV) in the presence of diisopropyl ethylamine in THF at 110 C in a sealed flask provided the secondary amine (XVI). Finally, the target compound was obtained by desilylation with tetrabutylammonium fluoride, followed by hydrogenolysis of the benzyl protecting group.