Johari Suzaimi, Johan Mohd Rafie, Khaligh Nader Ghaffari
Nanotechnology and Catalysis Research Center, Institute for Advanced Studies (IAS), University of Malaya, 50603 Kuala Lumpur, Malaysia.
Org Biomol Chem. 2022 Mar 16;20(11):2164-2186. doi: 10.1039/d2ob00135g.
Knoevenagel condensation reaction counts as a vital condensation in organic chemistry due to the synthesis of valuable intermediates, heterocycles, and fine chemicals from commercially available reactants through forming new CC bonds between an aldehyde or ketone and active methylene compounds. Therefore, the catalytic Knoevenagel condensation reaction has continuously received significant interest in different aspects, , investigating the catalytic efficiency of new heterogeneous and homogeneous catalysts. Furthermore, metal-free catalysis has recently attracted considerable attention because of environmental concerns. This review summarizes the most recent studies on utilizing metal-free nitrogen-based catalysts in the Knoevenagel condensation reaction, including organocatalysts, polymers, ionic liquids, and bio- and carbon-based catalysts. The substrate scope, the optimal reaction conditions, selectivity, the desired product yield, merits, and limitations of each method are discussed. In addition, the recyclability, biocompatibility, and biodegradability of catalysts are reported. This review also covers the approaches that influence the selectivity of the Knoevenagel products.
克诺文纳格尔缩合反应在有机化学中是一种重要的缩合反应，因为它能通过醛或酮与活性亚甲基化合物之间形成新的CC键，从市售反应物合成有价值的中间体、杂环化合物和精细化学品。因此，催化克诺文纳格尔缩合反应在不同方面一直备受关注，例如研究新型多相和均相催化剂的催化效率。此外，由于环境问题，无金属催化最近引起了相当大的关注。本综述总结了在克诺文纳格尔缩合反应中使用无金属氮基催化剂的最新研究，包括有机催化剂、聚合物、离子液体以及生物和碳基催化剂。讨论了每种方法的底物范围、最佳反应条件、选择性、目标产物产率、优点和局限性。此外，还报道了催化剂的可回收性、生物相容性和生物降解性。本综述还涵盖了影响克诺文纳格尔产物选择性的方法。
