Isoamyl Nitrite → Ethyl thiazole-5-carboxylate
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N[C:2]1[S:3][C:4]([C:7]([O:9][CH2:10][CH3:11])=[O:8])=[CH:5][N:6]=1.N(OCCC(C)C)=O>CN(C=O)C.C1COCC1>[CH2:10]([O:9][C:7]([C:4]1[S:3][CH:2]=[N:6][CH:5]=1)=[O:8])[CH3:11]N[C:2]1[S:3][C:4]([C:7]([O:9][CH2:10][CH3:11])=[O:8])=[CH:5][N:6]=1.N(OCCC(C)C)=O>CN(C=O)C.C1COCC1>[CH2:10]([O:9][C:7]([C:4]1[S:3][CH:2]=[N:6][CH:5]=1)=[O:8])[CH3:11]A solution of 2-amino-5-(ethoxycarbonyl)thiazole (50 g, 0.29 mmol) in a mixture of DMF (83 mL) and THF (31 7 mL) was added dropwise over 87 minutes to a stirred 41° C. solution of isoamyl nitrite (59 mL, 0.44 mol) in DMF (130 mL). A maximum temperature of 60° C. was observed during the exothermic addition. After another 40 minutes the THF was removed under vacuum at 45° C. The concentrated DMF solution was cooled to 25° C. and diluted with toluene (420 mL) and water (440 mL). The toluene layer was extracted with 3×120 mL water, then dried with Na2SO4 (50 g) for 1 hour. After filtration the toluene layer was stripped on a rotary evaporator at 50° C. bath temperature, then on a vacuum pump at 21° C. The crude residue containing the title compound weighed 65.6 g. This material was used directly in the next step. A sample of similarly prepared material was purified by column chromatography to give a yellow oil. 1H NMR (CDCl3) δ8.95 (s, 1H), 8.51 (s, 1H), 4.39 (q, 2H), 1.40 (t, 3H). 13C NMR (CDCl3) δ161.0, 157.9, 148.6, 129.8, 61.6, 14.1.
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