One‐pot green synthesis of benzoxazole derivatives through molecular sieve‐catalyzed oxidative cyclization reaction

Abstract

An one‐pot approach to benzoxazole ring from 2‐aminophenol and aldehydes utilizing molecular sieve as the catalyst have been developed. The new oxidative cyclization reaction excluded the usage of hazardous chemical reagents, transition‐metal catalysts, chemical oxidants, or strong acids, and, therefore, reduced the production of toxic chemical waste. This offers an environmentally friendly pathway for the synthesis of various benzoxazole derivatives.

OMS-2/H2O2/Dimethyl Carbonate: An Environmentally-Friendly Heterogeneous Catalytic System for the Oxidative Synthesis of Benzoxazoles at Room Temperature

“…So, in our catalytic system, H 2 O 2 was a superior and favorable environmentally friendly oxidant. As we known, previously reported oxidative cyclizations of phenolic imines were generally performed in polar and aprotic solvents, such as CH 2 Cl 2 , toluene and EtOAc, or alcohol. − When we used CH 2 Cl 2 as the solvent under the present conditions, the reaction proceeded faster in initial stage and led to full conversion and excellent yield in 6 h (Figure , right). Comparatively, the reaction in DMC proceeded slightly slow in initial stage but eventually showed a very similar kinetic profile like it was run in CH 2 Cl 2 .…”

“…Due to the ease in separation, recovery and recycling of catalysts, heterogeneous catalytic processes based on the aerobic cyclization of phenolic imines have also been realized in recent years. Recyclable Cu-based nanoparticles, Co-based nanocomposite, ZnO nanoparticles, active carbon, molecular sieve and polymer-incarcerated Pt nanoclusters have been found to be efficient heterogeneous catalysts associated with oxygen . However, in the aforementioned cases, base additives, elevated reaction temperatures or toxic catalyst and reaction solvents were employed to achieve satisfied catalytic performance.…”

New Method of 2-Arylbenzoxazole Synthesis from 2-Aminophenol Derivatives and Benzaldehyde Using Sulfur as an Oxidant

“…Các nghiên cứu trước đây để tổng hợp các dẫn xuất của thường bao gồm ngưng tụ 2-aminophenol với axit cacboxylic [3-4] hoặc dẫn xuất [5][6] trong điều kiện không oxy hóa hoặc với ancol [7][8], amin [9][10], ketone [11], aldehydes [12][13][14][15], methylarenes [16] hoặc các hợp chất liên quan [17] với sự có mặt của chất oxy hóa hoặc ở nhiệt độ cao [18][19]. Tuy nhiên, hầu hết các phương pháp tổng hợp truyền thống đều cần điều kiện axit mạnh, nhiệt độ cao và một lượng chất xúc tác đáng kể [14] (bao gồm cả chất xúc tác kim loại chuyển tiếp đắt tiền/độc hại) [5,7,13,[15][16][18][19][20][21] ISSN: 2734-9381 https://doi.org/10.51316/jst.148.etsd.2021.31.1.8 Received: June 23, 2020; accepted: October 16, 2020 cũng như thuốc thử và dung môi độc hại [3,4,8,12,16]. Mặc dù quá trình oxy hóa sử dụng oxi [12,15,[20][21] là phổ biến và thân thiện với môi trường.…”

Nanometric‐Thick Metal‐Free h‐Boron Nitride/Graphene Films as Base Catalyst for the Synthesis of Benzoxazoles

“…Among the few precedents, a study used commercial 5 Å molecular sieve [0.7 CaO:0.3 Na 2 O:1.0 Al 2 O 3 :2.0 SiO 2 :x H 2 O] as presumed a base catalyst. [19] Herein it will be reported that nanometer-thick films of single layer h-BN on few layers defective graphene films (h-BN/ fl-G films) promote the synthesis of benzoxazoles by coupling a 2-aminophenol with p-substituted benzaldehydes. Available CO 2 chemisorption measurements support that the catalytic activity of h-BN/fl-G films most likely derives from the presence of basic sites associated with the presence of atom vacancies in h-BN structure.…”