2.14 Other Condensation Reactions (Knoevenagel, Perkin, Darzens)

Room-Temperature Coupling/Decarboxylation Reaction of α-Oxocarboxylates with α-Bromoketones: Solvent-Controlled Regioselectivity for 1,2- and 1,3-Diketones

“…Following the coupling reaction process in NMP with TLC revealed the emergence of two new spots rather than the diketone products before addition of KOH. The major spot was determined by the X-ray diffraction analysis to be trans -methyl 3-benzoyl-2-phenyloxirane-2-carboxylate ( trans - 5aa ), a Darzens-type product (eq a and Figure S2, left). The minor spot was found to be cis - 5aa by using 1 H NMR and HRMS in comparison with trans - 5aa .…”

Room Temperature, Reductive Alkylation of Activated Methylene Compounds: Carbon–Carbon Bond Formation Driven by the Rhodium-Catalyzed Water–Gas Shift Reaction

“…With over 120 years worth of history and applications in synthetic endeavors, the Knoevenagel condensation reaction represents an indispensible tool in organic synthesis . The reaction entails the addition of an active methylene compound to an aldehyde or ketone followed by the elimination of water (Scheme a).…”

“…Because of its operational simplicity and expedited access to α,β-unsaturated motifs, the Knoevenagel condensation has found multiple applications in organic synthesis, including in industrial settings . One of its key features is the possibility to engage the resulting alkene in tandem processes, such as Michael, Diels–Alder, or sigmatropic reactions . In this context, the reductive variant of the Knoevenagel reaction, in which the alkene is hydrogenated immediately following the condensation (Scheme b), has also received significant attention.…”

Isocyanide-based three component reaction for synthesis of highly cyano substituted furan derivatives

“…15 This pioneering work of Knoevenagel have made impressive advances in the synthesis of ve and six membered homo and hetero-cyclic compounds. 16,17 Recently, Takahashi 18 and Nair 19 have subsequently reported the formation of dicynocyclopentene derivatives from intermolecular coupling of arylidenemalononitriles, alkynes and isocyanates or isocyanides, respectively. Later, dicyano-2,3-dihydro-1H-indene derivatives were synthesized via three-component reaction of 2-alkynylbenzaldehyde, malononitrile, and indole.…”