目的:在有机化学中建立绿色和可持续的Knoevenagel缩合反应仍然至关重要。这项工作旨在提供一种新的无金属和无卤素催化方法,用于在实验室和工业规模上合成CS和(het-ero-)亚芳基丙二腈。在乙醇中研究了各种羰基与丙二腈的Knoevenagel缩合反应,一种环保的媒介,在七种氮基有机催化剂的存在下。
方法:在Knoevenagel缩合反应中使用两种获得的和四种市售的基于氮的有机催化剂进行了比较研究。基于效率和绿色的方法,优化了使用封闭催化系统合成CS气体(2-氯亚苄基丙二腈)的方法。
结果:在短时间内获得了100%的转化率和优异的收率。产物可以直接从反应混合物中结晶。分离纯产品后,应溶液直接用于下一次运行,没有任何浓度,激活,净化,或分离。此外,使用咪唑作为选定的氮基催化剂,在五次连续运行中以95±2%的产率提供晶体产物。
结论:能源效率,节约成本,更环保的条件,仅使用5摩尔%的有机催化剂,催化剂的高可回收性,防止浪费,通过旋转蒸发器回收萃取剂,用于非结晶产品,证明了使用乙醇中的咪唑作为有效且高度可回收的催化系统的CS的潜在商业生产。
OBJECTIVE: The establishment of a green and sustainable Knoevenagel condensation reaction in organic chemistry is still crucial. This work aimed to provide a newly developed metal-free and halogen-free catalytic methodology for the synthesis of CS and (hetero-) arylidene malononitriles in the laboratory and industrial scale. The Knoevenagel condensation reaction of various carbonyl groups with malononitrile was investigated in ethanol, an ecofriendly medium, in the presence of seven nitrogen-based organocatalysts.
METHODS: A comparative study was conducted using two as-obtained and four commercially available nitrogen-based organocatalysts in Knoevenagel condensation reactions. The synthesis of CS gas (2-chlorobenzylidene malononitrile) using a closed catalytic system was optimized based on their efficiency and greener approach.
RESULTS: The conversion of 100% and excellent yields were obtained in a short time. The products could be crystallized directly from the reaction mixture. After separating pure products, the residue solution was employed directly in the next run without any concentration, activation, purification, or separation. Furthermore, the synthesis of 2-chlorobenzylidenemahmonitrile (CS) was carried out on a large scale using imidazole as a selected nitrogen-based catalyst, afforded crystalline products with 95 ± 2% yield in five consecutive runs.
CONCLUSIONS: Energy efficiency, cost saving, greener conditions, using only 5 mol% of organocatalyst, high recyclability of catalyst, prevention of waste, recycling extractant by a rotary evaporator for non-crystallized products, demonstrated the potential commercial production of CS using imidazole in ethanol as an efficient and highly recyclable catalytic system.