An overview of metal-free sustainable nitrogen-based catalytic knoevenagel condensation reaction
Suzaimi Johari, Mohd Rafie Johan, Nader Ghaffari Khaligh
Abstract
, 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.