Dimethyl Sulfoxide → 7-Bromo-4-chloro-2,6-dimethyl-5-{[2-(trimethylsilyl)ethoxy]methyl}-5H-pyrrolo[3,2-d]pyrimidine

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Reaction Steps

Sodium hydride (1.82 g; 45.60 mmol; 60% in oil, washed with hexane), is suspended in dry DMF (125 mL) and dry DMSO (25 mL). To the stirring suspension 7-Bromo-4-chloro-2,6-dimethyl-5H-pyrrolo[3,2-d]pyrimidine from example A8 (10.00 g; 38.00 mmol) dissolved in dry DMF (125 mL) is added dropwise within 30 minutes at ambient temperature. After complete addition the reaction mixture is stirred for one hour at ambient temperature. To the resulting solution 2-(trimethylsilyl)ethoxymethylchloride (8.74 mL; 49.40 mmol) is added dropwise and the reaction mixture is stirred for one hour at ambient temperature. After diluting with water/ice and dichloromethane, the organic layer is separated and the aqueous layer is extracted with dichloromethane (2×400 mL). The combined organic layers are dried over MgSO4 and filtered through a plug of neutral alumina (act. 2-3). The solvent is removed under reduced pressure and the residue is purified by column chromatography on silica gel (cyclohexane:ethylacetate/9:1) affording the title compound as a white solid.

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