The present communication describes the use of titania (TiO2) nanomaterials of different sizes (16 nm, 35 nm, 70 nm, 200 nm, and 1000 nm) as heterogeneous catalysts for the preparation of a series of medicinally significant poly-substituted quinoline derivatives via Friedlander hetero-annulation. These TiO2 nanomaterials exhibited remarkable catalytic activity with a high substrate to catalyst molar ratio (20 : 1) to achieve the synthetic targets in excellent yields ranging from 81–94%. The effect of catalyst particle size on the yield of the quinolines was also investigated. Yields of product were found to decrease when the TiO2 particle size increased from 16 nm to 1000 nm. GC-MS data indicated that TiO2 nanoparticles having 16 nm and 35 nm size of anatase phase provided better yields of the target compound, followed by particles of 70 nm in size, whereas 200 nm and 1000 nm size of anatase phase did not show the formation of the product under the same reaction conditions. The use of catalyst in solvent-free reaction conditions and its reusability up to five-cycles with similar catalytic response are the unique features of this heterogeneous catalysis. Furthermore, greater selectivity, cost-efficiency, clean reaction profiles, simple work-up procedure and high yield are the noteworthy features of this eco-friendly green protocol.
本文介绍了利用不同尺寸(16 nm、35 nm、70 nm、200 nm和1000 nm)的
二氧化钛(TiO2)纳米材料作为非均相催化剂,通过Friedlander杂环化反应制备一系列具有药用价值的多元取代
喹啉衍
生物。这些TiO2纳米材料显示出显著的催化活性,高底物与催化剂的摩尔比(20:1)可以在优异的产率(81-94%)内实现合成目标。还研究了催化剂粒径对
喹啉产率的影响。随着TiO2粒径从16 nm增加到1000 nm,发现产物产率下降。GC-MS数据显示,具有16 nm和35 nm尺寸的
金红石相TiO2纳米粒子提供了更好的目标化合物产率,其次是70 nm尺寸的粒子,而200 nm和1000 nm尺寸的
金红石相在相同反应条件下没有显示出产物的形成。在无溶剂反应条件下使用催化剂及其在五个循环内的可重复使用性与类似的催化响应是非均相催化的独特特点。此外,高选择性、成本效益、清洁反应过程、简单的后处理程序和高产率是这种环保绿色方案的显著特点。