Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Silica-supported organocatalysts

The preparation of immobilized catalysts related to the imidazolidinone-type organocatalyst 13 and their application in the asymmetric Diels-Alder reaction was reported by Pihko and co-workers [9]. The reactivity of the immobilized catalysts depended on the type of solid support. The silica-supported imidazolidinone 24, which was prepared starting from N-Fmoc-protected L-phenylalanine, was found to be a highly active organocatalyst. Several dienes and a,/i-un saturated aldehydes have been successfully used in the presence of only 3.3 to 20 mol% 24, usually... [Pg.260]

Monge-Marcet, A., Cattoen, X., Alonso, D.A., Najera, C, Man, M.W.C., and Pleixats, R. (2012) Recyclable silica-supported prolinamide organocatalysts for direct asymmetric aldol reaction in water. Green Chem, 14 (6), 1601-1610. [Pg.984]

The use of supported organocatalysts in flow chemistry is not new. A pioneering work using an organic base catalyst was reported by Venturello. Knoevenagel condensations of aromatic aldehydes, cyclohexanone, and acetophenone with acetoa-cetate, cyanoacetate, or malonate were catalyzed by aminopropyl-functionalized silica gel (56), which was packed in a gravity-fed column, under continuous-flow conditions (Scheme 7.40) [149]. A flowcell microreactor, whose wall surfaces were coated with aminopropylsilica, was utilized in Knoevenagel and Michael reactions [150]. [Pg.184]

Since the discovery of proline-catalyzed enantioselective aldol reactions, an extensive research program to explore chiral secondary amine catalysts has been pursued. Several polymer-supported chiral amines have been synthesized for aldol, Mannich, and related reactions. Polystyrene is a popular solid phase for use in place of silica gel in the proline-based organocatalysis. In contrast, silica gel displays a slightly acidic character and has a hydrogen-bond donor or acceptor, which may change the catalytic activity and chiral space of the organocatalyst. Flow enantioselective aldol [158-161], Mannich [162], Michael [163], and related reactions... [Pg.185]

Organocatalysts are often nonionic liquid modified-silica, polyelectrolytes, montmorillonite, or P-cyclodextrin. Although bond strength in non-covalently supported catalyst is weak, the catalyst itself is directly used for immobihzation without the need for modification or synthetic steps required for covalent attachment to support [113],... [Pg.832]


See other pages where Silica-supported organocatalysts is mentioned: [Pg.290]    [Pg.45]    [Pg.44]    [Pg.626]    [Pg.1431]    [Pg.626]    [Pg.265]    [Pg.76]    [Pg.499]    [Pg.249]    [Pg.256]    [Pg.276]    [Pg.318]    [Pg.185]    [Pg.195]    [Pg.379]    [Pg.626]    [Pg.664]    [Pg.664]    [Pg.665]    [Pg.667]    [Pg.831]    [Pg.962]    [Pg.626]    [Pg.646]    [Pg.664]    [Pg.664]    [Pg.665]    [Pg.667]    [Pg.831]    [Pg.962]    [Pg.90]   
See also in sourсe #XX -- [ Pg.626 ]




SEARCH



Silica support

Supported organocatalysts

© 2024 chempedia.info