Recycling organocatalysts

Gruttadauria, M., Giacalone, F. and Noto, R. (2008) Supported proline and proline-derivatives as recyclable organocatalysts. Chemical Society Reviews, 37 (8), 1666-1688. 

Ni, B., Zhang, Q. and Headley, A.D. (2007) Functionalized chiral ionic liquid as recyclable organocatalyst for asymmetric Michael addition to nitrostyrenes. Green Chem., 9 (7), 737-739. 

Fig. 2.6 Recyclable organocatalysts for the conjugate addition of aldehydes to nitroolefins...

Roy SR, Jadhavar PS, Seth K, Sharma KK, Chakraborti AK (2011) Organocatalytic application of ionic liquids [bmim][MeSOJ as a recyclable organocatalyst in the multi-component reaction for the preparation of dihydropyrimidinones and thiones. Synthesis 2011 2261-2267... 

Keywords Pyruvates, aromatic amines, aldehydes, fluorous imine-l,2-b/s(carbothioate) (I), recyclable organocatalyst, acetonitrile, room temperature, one-pot three-component condensation reaction, pyrrole-2-ones, l,5-dihydro-2//-pyrrole-2-ones... 

Khan, S. S. J. Shah and J. Liebscher (2011). "Ionic-liquid tagged prolines as recyclable organocatalysts for enantioselectiive a-aminoxylations of carbonyl compounds." Tetrahedron Vol.67, 0an 15, 2011), pp. 1812-1820 ISSN 0040-4020... 

Li, P.H., Wang, L., Zhang, Y.C., and Wang, G.W. (2008) Sihca gel supported pyrrohdine-based chiral ionic liquid as recyclable organocatalyst for asymmetric... 

A. Ueno, Y. Kayaki, T. Ikariya, Cycloaddition of tertiary aziridines and carbon dioxide using a recyclable organocatalyst, 1,3-dl-tert-butylimidazolium-2-carboxylate a straightforward access to 3-subsfituted 2-oxazoKdones, Green Chem. 15 (2013) 425-430. 

Zhou, L. and Wang, L. (2007) Chiral ionic liquid containing L-proline unit as a highly efficient and recyclable asymmetric organocatalyst for aldol reaction. Chem. Lett., 36 (5), 628-629. 

Several organocatalysts have been recycled efficiently (selected examples are shown in Scheme 14.2). For example, the Jacobsen group has reported results from an impressive study of the recycling of the immobilized urea derivative 6, a highly efficient organocatalyst for asymmetric hydrocyanation of imines (Scheme 14.2) [11]. It was discovered that the catalyst can be recycled and re-used very efficiently - over ten reaction cycles the product was obtained with similar yield and enantioselectivity (96-98% yield, 92-93% ee). 

In addition, minor variation of the catalyst in combination with immobilization on a resin support gave an analogous recyclable solid-supported organocatalyst. Varying the derivatization method by trapping the a-amino nitrile intermediate with formic acid and acetic anhydride gives the crystalline formamides 19 in excellent yield and with high enantioselectivity. These features of this catalytic process have been demonstrated by results from the synthesis of r-tert-leucine (Scheme 14.8) [49]. 

Bensa, D., Constantieux, T. and Rodriguez, J. (2004) P-BEMP a new efficient and commercially available user-friendly and recyclable heterogeneous organocatalyst for the Michael addition of 1,3-dicarbonyl compounds. Synthesis, 923-927. 

Wang and coworkers synthesised recyclable and reusable pyrrolidine-fluorosulfonamide organocatalysts 3b,c. The fluorous sulfonamide organocatalyst 3b was used for the Michael addition of ketones and aldehydes to nitro-olefins in water, and the reaction gave products with high enantio- and diastereomeric purity. Robust organocatalyst 3b was easily separated from... 

Scheme 9.22 Recyclable and reusable pyrrolidine fluorous sulfonamide organocatalysts.

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