3-(2-(tert-Butyldimethylsilyloxy)ethyl)-2-fluorobenzaldehyde [Aromatic Intermediate 5] (4.07 g) was added to (2-isopropylthiazol-4-yl)(1-oxa-4,9-diazaspiro[5.5]undecan-4-yl)methanone trifluoroacetate [Example 1, step b] (6.10 g) in a mixture of N-methyl-2-pyrrolidinone (50 mL) and acetic acid (0.83 mL) and stirred for 30 min. Sodium triacetoxyborohydride (4.58 g) was then added and the mixture stirred overnight. The reaction mixture was poured into water (100 mL), the pH was adjusted to 8 using saturated sodium bicarbonate solution, and the mixture was extracted with ethyl acetate (3×100 mL). The combined organic phases were washed with water (3×100 mL) and brine (100 mL), dried over sodium sulphate, filtered and evaporated. The residue was purified by flash silica chromatography using 77.5:17.5:5 isohexane:ethyl acetate:triethylamine as solvent to give the subtitled compound as a clear oil. Yield 5.35 g.
