[C:1]([NH:5][CH2:6][Si:7]([CH3:10])([CH3:9])[CH3:8])([CH3:4])([CH3:3])[CH3:2].[CH2:11]=O.CO.[C:15](=[O:18])([O-])[O-].[K+].[K+]>O>[C:1]([N:5]([CH2:11][O:18][CH3:15])[CH2:6][Si:7]([CH3:10])([CH3:9])[CH3:8])([CH3:4])([CH3:3])[CH3:2]N-tert-Butyl-N-(trimethylsilylmethyl)amine 77 (8.47 g, 53.1 mmol) was added dropwise, over approximately 30 min, via a pressure equalizing addition funnel to a stirred solution of aqueous formaldehyde (5.98 mL of a 37 wt. % solution in water, 79.7 mmol) at 0° C. After 45 min, methanol (6.45 mL, 159.3 mmol) was added and the resulting solution was saturated with potassium carbonate. After stirring vigorously for approximately 5 h, the aqueous phase was removed. The organic phase was saturated with potassium carbonate and stirred overnight. The reaction mixture was poured into water and extracted three times with diethyl ether. The combined organic extracts were washed with brine, dried (MgSO4) and the volatiles evaporated in vacuo. Distillation (high vacuum; ˜70° C.) of the residual liquid afforded the title compound 78 as a colorless liquid.
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