Catalytic procedures for multicomponent synthesis of imidazoles: selectivity control during the competitive formation of tri- and tetrasubstituted imidazoles
作者:Dinesh Kumar、Damodara N. Kommi、Narendra Bollineni、Alpesh R. Patel、Asit K. Chakraborti
DOI:10.1039/c2gc35277j
日期:——
based ionic liquids (organic salts) were investigated for the three component reaction (3-MCR) of 1,2-diketone, aldehyde, and ammonium salts to form 2,4,5-trisubstituted imidazoles and the four component reaction (4-MCR) involving 1,2-diketone, aldehyde, amine and ammonium acetate to form 1,2,4,5-tetrasubstituted imidazoles. The HBF4–SiO2 was found to be the stand out catalyst for both the 3-MCR and
不同的氟硼酸衍生的催化剂体系的催化潜力,即。研究了HBF 4水溶液,固体负载的HBF 4,金属四氟硼酸盐(无机盐),固体负载的金属四氟硼酸盐和基于四氟硼酸盐的离子液体(有机盐)对1,2-二酮,醛的三组分反应(3-MCR)和铵盐形成2,4,5-三取代的咪唑,然后进行涉及1,2-二酮,醛,胺和乙酸铵的四组分反应(4-MCR),形成1,2,4,5-四取代的咪唑。发现HBF 4 -SiO 2是3-MCR和4-MCR工艺的杰出催化剂。其次最有效的催化剂是LiBF 4和Zn(BF 4)2分别通过3-MCR和4-MCR形成2,4,5-三取代和1,2,4,5-四取代的咪唑。这是有关4-MCR过程中涉及1,2-二酮,醛,胺和乙酸铵的2,4,5-三取代咪唑竞争形成的未解决问题的第一份报告,并着重指出了催化剂体系在控制催化剂中的影响。选择性形成四取代的咪唑。弱质子酸的金属盐以四氟硼酸盐>高氯酸盐>三氟甲磺酸酯的