5-ethoxy-2-phenyl-4- oxazole

Methyl-2-phenyl-oxazol-4-yl)ethoxy]benzo[2]thiophen-7-yl]methyl]-thiazolidine-2,4-dione. 

Preparation of 5-(3-(2-(5-methyl-2-phenyl-oxazol-4-yl)ethoxy)benzyl)-2-phenyl-4-A-phenylamido-l, 2,3-triazole... 

Oxazol 5-(4-Brom-phenyl)-4-ethoxy-5-methyl-4,5-dihydro-E19d, 682 (R-NC + Keton)... 

Imidazol 5-Ethoxy-t-hydroxy-2-(2-hydroxy-phenyl)-4-methyl- E8c, 52 [HO — N = C(CH3) — COOC2H5 + Ar—CH = N —OH] Malonaldehydsaure [a-(Hydroxy-methyl)-4-methoxy-benzyliden]- -amid E15/1, 682 (aus 4,5-H2-1,2-oxazol)... 

The authors adapted this methodology to prepare 3,3,3-trifluoroalanine 220. Benzamide was first converted to 217 (Ar = CgHs) followed by reductive cyclization to 5-fluoro-2-phenyl-4-(trifluoromethyl)oxazole 218 (Ar = C6H5). Displacement of fluoride in 218 gave 5-ethoxy-2-phenyl-4-(trifluoromethyl)oxazole 219, which was converted to 220 with iodotrimethylsilane (Scheme 1.61). 

Turchi and Cullen described the first examples of pyrazoles prepared from oxazoles (Scheme 1.231). Treatment of 5-ethoxy-p-oxo-2-phenyl-4-oxazolepropa-noic acid ethyl ester 857 with hydrazine did not afford the expected pyrazolone 858. Instead, the authors isolated ethyl-4-(benzoylamino)-5-ethoxy-l//-pyrazole-3-acet-ate 860 (R = H) in good yield. Similarly, reaction of 857 with methyUiydrazine produced 860 (R = CH3) in comparable yield. 

An oxazole-alkene Diels-Alder reaction has also been used to synthesize a tri-fluoromethylated pyridine related to pyridoxol. 5-Ethoxy-4-(trifluoromethyl)-2-oxazolecarboxylic acid 41 decarboxylated and then reacted with acrylic acid to give the expected 3-hydroxy-2-(trifluoromethyl)pyridine-4-carboxylic acid 42 in 63% yield (Fig. 3.13)." The electron-withdrawing trifluoromethyl group of 41 strongly modulates its reactivity, however, and it does not react with ethyl acrylate or A-phenyl maleimide. 

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