CCOC(=O)c1cnc(N)o1.O=[N+]([O-])c1ccc(Cl)nc1>C1COCCO1.CC1(C)c2cccc(P(c3ccccc3)c3ccccc3)c2Oc2c(P(c3ccccc3)c3ccccc3)cccc21.O=C(/C=C/c1ccccc1)/C=C/c1ccccc1.O=C(/C=C/c1ccccc1)/C=C/c1ccccc1.O=C(/C=C/c1ccccc1)/C=C/c1ccccc1.O=C([O-])[O-].[Cs+].[Cs+].[Pd].[Pd]>CCOC(=O)c1cnc(Nc2ccc([N+](=O)[O-])cn2)o1Objective: Test of substrate scope in couple of ester substituted aminooxazole To an oven-dried microwave vial 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) 2-chloro-5-nitropyridine (158 mg, 1.00 mmol) and (9,9-dimethyl-9H-xanthene-4,5-diyl)bis(diphenylphosphine) (43.4 mg, 0.07 mmol) and the vial was capped and purged with nitrogen. dioxane (4 mL) (degassed) was added and the reaction mixture was heated to 160 °C for 1 h under microwave irradiation. LCMS of the crude reaction mixture indicated that the desired product had been formed while only a trace of the amine starting material remained. DCM (20 mL) was added to the crude reaction mixture together with silica (2 g) and the solvent was removed under reduced pressure. The resulting residue was then placed in a dry-load tube prior to chromatography. The crude product was purified by flash silica chromatography, elution gradient 0 to 2.5% methanolic ammonia in DCM. Pure fractions were evaporated to dryness to afford ethyl 2-(5-nitropyridin-2-ylamino)oxazole-5-carboxylate (238 mg, 86 %) as a orange solid.
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