Реакция #452
ord-345c2935b6ec4f748049eeb832f405b7
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Objective: Comparison of the reactivity of 2-aminooxazole and ester substituted 2-aminooxazole under identical reaction conditions. To an oven-dried round bottomed flask was added ethyl 2-aminooxazole-5-carboxylate (156 mg, 1.00 mmol), cesium carbonate (651 mg, 2.00 mmol), TRIS(DIBENZYLIDENEACETONE)DIPALLADIUM(0) (22.87 mg, 0.02 mmol), (9,9-dimethyl-9H-xanthene-4,5-diyl)bis(diphenylphosphine) (43.4 mg, 0.07 mmol) and 2,4-dichloropyridine (0.108 mL, 1.00 mmol). A reflux condenser was fitted and the vessel was purged with nitrogen. dioxane (2 mL)/DMSO (2 mL) (degassed) was added and the reaction mixture was heated to 100 °C for 16 h. The crude product was purified by ion exchange chromatography, using an SCX column. The desired product was eluted from the column using 7M NH3/MeOH and pure fractions were evaporated to dryness to afford the crude product. The crude product was purified by flash silica chromatography, elution gradient 1 to 3% methanolic ammonia (7 M) in DCM. Pure fractions were evaporated to dryness to afford ethyl 2-(4-chloropyridin-2-ylamino)oxazole-5-carboxylate (128 mg, 47.9 %) as a pale yellow solid. Conclusion: The desired product was formed in moderate yield. Normal-phase column DCM:methanolic ammonia