Asymmetric Henry reaction of aldehydes catalyzed by recyclable an MCM-41 supported copper(II) salen complex

Ba/ZrO2 nanoparticles as efficient heterogeneous base catalyst for the synthesis of β-nitro alcohols and 2-amino 2-chromenes

“…18,19 Various homogeneous and heterogeneous catalytic systems studied for this reaction include amine-MCM-41 hybrids, MCM-41-Cu(salen) complex, I 2 /K 2 CO 3 , polyamine functionalized mesoporous zirconia, silica-supported amine catalysts, and CsF/[bmim][BF 4 ] ionic liquids. [20][21][22][23] Many of the reported method employ homogeneous catalyst, supported reagents or covalently grafted organic bases which suffer from various issues such as catalyst stability, recyclability, regeneration and harsh reaction condition. It is therefore highly desirable to develop novel catalytic protocols using heterogeneous base catalysts which are stable, inexpensive, and recyclable, which can catalyze the β-nitro alcohol formation reaction under mild conditions.…”

Nanostructured Catalysts for the Aldol, Knoevenagel, and Henry Reactions

“…Hence, an asymmetric Henry reaction with impressive enantioselectivities can be realized by developing catalysts with efficient enantioselective catalytic properties. Recently, Dhahagani et al 62 synthesized a chiral mesoporous MCM-41-catalyst modified with Cu(salen) complex that catalyzed the asymmetric nitroaldol reaction between benzaldehyde and nitroalkane in the presence of morpholine as an additive ( while morpholine acted as a base to activate nitromethane. Other metal-salen complexes were also tested for the same reaction, but copper-salen was the one that gave the best yield and enantiomeric excess (ee) ( Table 7.1).…”

“…62 By using the material as a heterogeneous catalyst, the authors then demonstrated the Knoevenagel condensation reaction between an aldehyde or a ketone and ethyl cyanoacetate, which yielded the corresponding olefins (or the condensation products) without any alcohol or other side products. In the catalytic reaction, whereas the aromatic aldehydes were found to be more readily reactive under milder reaction condition (303 K) giving higher conversions, the aromatic ketones reacted well enough only at higher temperatures (e.g., 353 K) and also gave only lower reactant conversions even at such higher temperature.…”

Synthesis of chiral salalen ligands and their in‐situ generated Cu‐complexes for asymmetric Henry reaction

“…[53][54][55][56][57][58][59][60][61] Salen ligands are one of the most privileged ligands for the asymmetric catalysis, and Cu (II) complexes of salen and salan ligands were largely used for nitro-aldol reaction and efficiently active at mild reaction conditions. [62][63][64][65][66][67][68][69][70][71][72] (S)-Proline-based single chiral center salalen and salan ligands were first reported by Katsuki and co-workers for the asymmetric epoxidation of non-functionalised alkenes. 73 These ligands were also used by Kol and co-workers for polymerisation of α-olefins and stereoselective polymerization of lactide.…”