A Decade Update on Benzoxazoles, a Privileged Scaffold in ­Synthetic Organic Chemistry

Abstract

In 2014, more than 80% of the marketed drugs in the US contained heterocyclic compounds, which play a major role in the drugdiscovery process, as one of the primary components. Benzoxazole, consisting of an oxazole ring fused with a benzene ring, has shown profound impact in drug discovery research owing to its important bioactivity. This moiety has also shown important properties in material science. The synthesis of this privileged scaffold from readily available chemicals remains a primary focus for the synthetic chemistry community. In this review, efforts have been made to focus on the latest information available on the different synthetic strategies such as solution phase, multicomponent, green and solid phase chemistry and applications of different benzoxazole derivatives. Furthermore, the updated synthetic information incorporated in this review article will help to improve future synthesis of this scaffold. Conclusion and Outlook

A New Method for the Synthesis of 2-Substituted Benzoxazoles from 2-Nitrophenol Derivatives and Aldehydes

“…Các dẫn xuất của axit carboxylic cũng được sử dụng như acid chloride, nitrile, imidate, orthoester, anhydride, lactone... [4]. Mặt khác, aldehyde có thể được sử dụng cùng các chất oxy hóa khác nhau, chẳng hạn như nitrobenzene, benzoquinone, sodium metabisulfite, oxit thủy ngân, chì tetraacetate, iốt, đồng(II) acetate, và không khí được sử dụng cho mục đích này [4] xúc tác và chất oxy hoá đắt tiền, có cấu trúc phức tạp, đòi hỏi áp suất cao, nhiệt độ cao và dưới điều kiện chiếu xạ vi ba [5]. Mặt khác, tổng hợp các dẫn xuất của benzoxazole thường đi theo con đường truyền thống không trải qua quá trình oxi hóa khử (sơ đồ 1).…”

Phosphonium acidic ionic liquid: an efficient and recyclable homogeneous catalyst for the synthesis of 2-arylbenzoxazoles, 2-arylbenzimidazoles, and 2-arylbenzothiazoles

“…11-14 Its structure was then authenticated by 1 H-NMR, 13 C-NMR, FT-IR and TGA. An equimolar mixture of triphenylphosphine and 1,4-butane sultone in toluene solvent (10 mL) was stirred and heated at reux for 12 h to obtain the zwitterion as a white solid.…”

“…The nal product was obtained aer solvent removal by a rotary evaporator followed by the purication on a silica gel column chromatography using acetone/petroleum ether (1/19) as an eluent solvent. The structural characterization was performed using 1 H, 13 C-NMR, and GC-MS. The recovered catalyst was reactivated by heating under reduced vacuum at 80 C for 30 min and reused for next cycles.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12] To date, there have been two pathways for the preparation of these compounds. 13 The rst one relying on the metal-catalyzed crosscoupling is more competent.…”

Synthesis and evaluation of new benzoxazole derivatives as potential antiglioma agents

“…Benzoxazoles represent an important class of chemical entities in medicinal chemistry as building blocks for modulating a ligand's affinity and/or selectivity towards a particular target and therefore benzoxazole scaffold is often found in ligands targeting a plethora of receptors and enzymes. Benzoxazole derivatives have been reported to show a wide range of biological activities such as antibacterial, antifungal, antiviral, anticancer, and antioxidant activities [4][5][6]. In particular, recent studies have indicated that benzoxazole derivatives show potent antitumor activity against different cancer cell lines [7][8][9][10][11][12] through the inhibition of Aurora B kinase [8], cyclooxygenase-2 (COX-2) [9,10], topoisomerase II [11] and the induction of Caspase-3 dependent apoptosis [12].…”