Knoevenagel reaction synthetic applications

Furthermore, the carbanion also may be added to a carbonyl group of another molecule, with formation of a new CC bond. Synthetic applications are the aldol condensation and the diacetonealcohol condensation. The acid strength of CH bonds in alpha position to COO-, COOR, or CN groups is extremely low (p > 20) and condensation reactions of the corresponding anions must be carried out in the absence of water (Claisen, Perkin, and Knoevenagel condensations). 

Early reviews B. Blagoev, D. Ivanov, Synthesis 1970, 615 D. Ivanov etal., ibid. 1975, 83. Synthetic application Y. A. Zhdanov etal, Carbohyd. Res. 29,274 (1973). Kinetic and mechanistic study J. Toullec etal, J. Org. Chem. 50,2563 (1985). Stereoselectivity M. Mladenova etal. Tetrahedron 37,2157 (1981) M. Momtchev etal. Bull Soc. Chim. France 5, 844 (1985). Cf. Aldol Reaction Knoevenagel Condensation. 

In particular, we have described selected examples of the application of monofunctional supported catalysts in reactions of considerable synthetic interest such as aldol, Michael and Knoevenagel condensations. In general. 

Coumarin synthetic routes include Perkin, Knoevenagel, Reformatsky, and Pechmann reactions. Among them Pechmann reaction has been proven to be superior regarding different issues and aspects. Pechmann found that coumarin derivatives are synthesized when the P-ketonic esters are condensed with phenols in the presence of concentrated sulfuric acid. The process and course of this reaction depends on the nature of the phenols, the beta-ketonic esters, and the catalyst. Since then, the use of this superior and practical protocol has become a vibrant area of study, and it has found applications as central strategic choice in the synthesis of an extensive selection of coumarin derivatives. 

---