B.CSC.[CH3:5][O:6][C:7]1[CH:8]=[C:9]([CH:23]=[CH:24][C:25]=1[O:26][CH3:27])[O:10][CH:11]([C:15]1[CH:22]=[CH:21][C:18]([C:19]#[N:20])=[CH:17][CH:16]=1)[CH2:12][CH:13]=[CH2:14].O.B1([O-])O[O:30]1.O.O.O.O.[Na+]>C1COCC1>[CH3:5][O:6][C:7]1[CH:8]=[C:9]([CH:23]=[CH:24][C:25]=1[O:26][CH3:27])[O:10][CH:11]([C:15]1[CH:22]=[CH:21][C:18]([C:19]#[N:20])=[CH:17][CH:16]=1)[CH2:12][CH2:13][CH2:14][OH:30]Borane-methyl sulfide complex (2 M in ether, 11 mL, 22 mmol) was added dropwise to a cooled (−5° C.) solution of 4-[1-(3,4-dimethoxy-phenoxy)-3-butenyl]benzonitrile (from step (a) above; 17.6 g, 56.8 mmol) in dry THF (15 mL) over a period of 15 minutes (during which time the reaction temperature rose to 0° C.). The resulting mixture was stirred at between 0 and 10° C. for 1.5 h, before being allowed to warm to rt. Stirring was continued for a further 3.5 h at this temperature before water (22 mL) and sodium perborate tetrahydrate (11 g, 66 mmol) were added. The biphasic mixture was stirred for 2 h at rt before the water layer was separated and extracted with ether. The combined organic layers were washed with brine, dried and concentrated in vacuo. The resulting residue was purified by chromatography on silica gel, eluting with IPA:ethyl acetate:heptane (5:25:76) to yield 14.5 g (77%) of the sub-title compound.
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