Synthesis
The general procedure for the synthesis of 4-(4-nitrophenyl)oxazole from 4-phenyloxazole was as follows: referring to the method of Example 13, 4-phenyloxazole (1 g, 6.89 mmol) was dissolved in concentrated sulfuric acid (5 mL) at 0°C. Subsequently, a cold solution of a pre-prepared nitration mixture (which was prepared from 3 mL of concentrated hydrochloric acid and nitric acid in 5 mL of ice-cold concentrated sulfuric acid) was slowly added over a period of 10 minutes. The reaction mixture was gradually warmed up to room temperature with continuous stirring. Upon completion of the reaction, the resulting solution was slowly poured into ice water to produce a white precipitate, which was collected by filtration and washed well with water. The solid product was dissolved in dichloromethane (DCM) and the organic phase was washed sequentially with water and brine. Finally, the organic phase was dried with anhydrous sodium sulfate and concentrated to give the target product 4-(4-nitrophenyl)oxazole (550 mg, 42% yield) as a white solid.
References
[1] Patent: WO2008/62182, 2008, A1. Location in patent: Page/Page column 113
[2] Journal of Organic Chemistry, 1990, vol. 55, # 3, p. 929 - 935
