[CH3:1][C:2]([CH3:16])([CH2:7][O:8][Si:9]([C:12]([CH3:15])([CH3:14])[CH3:13])([CH3:11])[CH3:10])[CH2:3][CH2:4][C:5]#N.[H-].C([Al+]CC(C)C)C(C)C.C([O:29]CC)C.Cl>C(Cl)Cl>[CH3:1][C:2]([CH3:16])([CH2:7][O:8][Si:9]([C:12]([CH3:15])([CH3:14])[CH3:13])([CH3:11])[CH3:10])[CH2:3][CH2:4][CH:5]=[O:29]
To a cooled (-78° C.) solution of 4.5 g (18.6 mmol) of 4,4-dimethyl-5-t-butyldimethylsilyloxyvaleronitrile in 36 mL of dry CH2Cl2 was added dropwise, over 30 min., 20.4 mL (20.4 mmol;1.1 eq) of a 1.0M solution of diisobutyl-aluminum hydride in CH2Cl2. After stirring for 2 h at -78° C., the cooling bath was removed and the solution allowed to warm to 0° C. To the crude (0° C.) reaction mixture was added 50-60 mL of ethyl ether, followed by the cautious addition of 10% HCl, until the mixture became strongly acidic (pH=1-2). Separation of the layers and three extractions of the aqueous phase with 100 mL ether, drying over MgSO4 and concentrating the combined organic layers gave 3.6 g (79%) of the title compound as a faint yellow oil, sufficiently pure to be used in the next step. TLC: (Silica) Rf 0.28 (CH2Cl2 /pentane 3:7), detection with Purpald.
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