Imidazole → (S)-tert-butyl 1-(tert-butyldimethylsilyloxy)-3-cyclopropylbut-3-en-2-ylcarbamate

Participants

Reaction Conditions

Reaction Steps

To a solution of (S)-tert-butyl 4-(1-cyclopropylvinyl)-2,2-dimethyloxazolidine-3-carboxylate (Intermediate 232, 8.25 g, 30.86 mmol) in methanol (100 mL) at room temperature was added p-toluenesulfonic acid monohydrate (1.174 g, 6.17 mmol). The reaction mixture was heated to 80° C. overnight. Another 0.2 eq of p-toluenesulfonic acid monohydrate was added. Continue heating at 80° C. for 2 hours. The reaction mixture was cooled to room temperature. Triethylamine (4.29 mL, 30.86 mmol) and di-tert-butyl dicarbonate (3.37 g, 15.43 mmol) were added. The reaction mixture was stirred over the weekend then concentrated. The residue was dissolved in ethyl acetate and washed once with saturated sodium bicarbonate. The combined organic extracts were dried over magnesium sulfate, filtered and concentrated. The resulting oil was dissolved in DCM (100 mL). Imidazole (2.73 g, 40.11 mmol), 4-dimethylaminopyridine (0.754 g, 6.17 mmol) and tert-butyldimethylsilyl chloride (4.65 g, 30.86 mmol) were added and the reaction mixture was stirred overnight at room temperature. The reaction mixture was filtered to remove solids and washed with brine twice. The organic layer was dried over magnesium sulfate, filtered and concentrated. Silica gel chromatography (0%-10% ethyl acetate/hexanes) afforded the title compound as a colorless oil (6.77 g, 64%).

Provenance & Evidence