Synthesis
2-Amino-4-bromophenol (2 g, 10.64 mmol) was mixed with 30 ml of triethyl orthoformate under the protection of nitrogen atmosphere and the reaction was heated to reflux for 8 hours. The reaction progress was monitored by thin layer chromatography (TLC). After completion of the reaction, the reaction mixture was cooled to room temperature. The solvent was removed by distillation to obtain the crude product. The residual triethyl orthoformate was subsequently removed under reduced pressure. Finally, purification by column chromatography gave 1.89 g of white solid product 5-bromobenzoxazole in 89.5% yield.
References
[1] Journal of Medicinal Chemistry, 2017, vol. 60, # 14, p. 6337 - 6352
[2] Patent: CN108503634, 2018, A. Location in patent: Paragraph 0316; 0317; 0318; 0319
[3] Organic Letters, 2011, vol. 13, # 3, p. 522 - 525
[4] Patent: WO2015/162538, 2015, A1. Location in patent: Page/Page column 47
[5] Tetrahedron Letters, 2015, vol. 56, # 3, p. 511 - 513
