Tetramethoxysilane → 6-Benzyloxy-3-(2-methoxy-5-nitrobenzylidene)-2,2-dimethylchroman-4-one

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Reaction Conditions

Reaction Steps

A mixture of 5.0 g (17.7 mmole) of the product of Example 100, 1.1 g (19 mmol) potassium fluoride, 3.5 g (19.5 mmole) 2-methoxy-5-nitrobenzaldehyde and 2.9 mL (2.97 g, 19.5 mmole) tetramethylortho-silicate in 15 mL dimethylformamide was heated at 80° C. for 7 hours. The mixture was poured into water and extracted with ethyl acetate. The ethyl acetate extract was and washed successively with 1N HCl, 5% NaHCO3, water and brine and then dried (MgSO4) and concentrated to give an oil. Flash chromatography on silica gel eluting with 30% ethyl acetate in hexanes gave 6.23 g (79%) of a foam. Recrystallization from ethyl acetate in hexanes yielded the title product as a solid m.p. 110°-112° C. NMR (CDCl3): δ1.70 (s, 6H); 3.82 (s, 3H); 5.02 (s, 2H). Analysis calculated for C20H23NO6 : C, 70.10; H, 5.20; N, 3.14. Found: C, 70.19; H, 5.21; N, 3.14.

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