Fe/S-Catalyzed synthesis of 2-benzoylbenzoxazoles and 2-quinolylbenzoxazoles <i>via</i> redox condensation of <i>o</i>-nitrophenols with acetophenones and methylquinolines
作者:Le Anh Nguyen、Thi Thu Tram Nguyen、Quoc Anh Ngo、Thanh Binh Nguyen
DOI:10.1039/d1ob00976a
日期:——
An Fe/S catalyst generated in situ from FeCl2·4H2O and elemental sulfur S8 in the presence of a tertiary amine as a base was found to catalyze efficiently a 6e− redox condensation of o-nitrophenols with acetophenones and methylquinolines. The condensed products 2-benzoylbenzoxazoles and 2-quinolylbenzoxazoles were obtained in reasonable yields with water as the only byproduct at a temperature as low
发现在叔胺作为碱存在下由 FeCl 2 ·4H 2 O 和元素硫 S 8原位生成的 Fe/S 催化剂可有效催化邻硝基苯酚与苯乙酮和甲基喹啉的 6e -氧化还原缩合反应。缩合产物 2-苯甲酰基苯并恶唑和 2-喹啉基苯并恶唑在低至 80 °C 的温度下以合理的收率获得,水作为唯一的副产物。
Palladium-catalyzed direct heteroarylation of chloropyridines and chloroquinolines
PdCl(dppb)(C3H5) as a catalyst, a range of heteroaryl derivatives undergoes coupling via C–Hbondactivation/functionalization reaction with chloropyridines or chloroquinolines in low to high yields. This air-stable catalyst can be used with a wide variety of substrates. The position of the chloro substituent on pyridines has a minor influence on the yields. On the other hand, the nature on the heteroaryl derivative
芳基氯化物与杂芳烃的直接偶联将具有可持续发展的巨大优势,因为它们的成本更低,质量更轻,可用化合物的多样性更大,并且还因为仅形成了与副产物碱有关的HCl和减少制备这些化合物的步骤数。我们观察到通过使用PdCl(dppb)(C 3 H 5)作为催化剂,一系列杂芳基衍生物通过C–H键活化/官能化反应与氯吡啶或氯喹啉进行低至高收率的偶联。这种空气稳定的催化剂可与多种基材一起使用。吡啶上氯取代基的位置对收率影响很小。另一方面,杂芳基衍生物的性质具有很大的影响。使用苯并恶唑,噻吩或噻唑衍生物可获得最高的收率。氯吡啶与呋喃的偶联也得到了预期的产物,但是产率低至中等。
Organocatalytic functionalization of heteroaromatic N-oxides with C-nucleophiles using in situ generated onium amide bases
Organocatalytic functionalization of heteroaromatic N-oxides was investigated using in situ generated onium amide bases, and C-nucleophiles were efficiently introduced by the sequential addition–elimination reaction under metal-free conditions, affording 2-substituted nitrogen heteroaromatics generally in good to high yields.
Benzoxazoles, benzothiazoles and benzimidazoles having substituents on the azole and benzene nuclei were synthesized evaluated for antifungal, insecticidal and herbicidal activities. It was found that benzimidazoles tended to exhibit antifungal activity while benzothiazoles tended to show herbicidal activity. Chloro, trifluoromethyl, methoxy and ethoxy groups at the 5 position were potent substituents, and the 2-pyridyl group at the 2 position is a common structural unit. Among several active derivatives, 7-chloro-2-(2-pyridyl) benzimidazole and 2-(2-pyridyl)-5-trifluoromethylbenzothiazole exhibited significant activity against Panonycus citri.