1040729-14-3Relevant articles and documents
An effective heterogeneous l-proline catalyst for the direct asymmetric aldol reaction using graphene oxide as support
Tan, Rong,Li, Chengyong,Luo, Jianqing,Kong, Yu,Zheng, Weiguo,Yin, Donghong
, p. 138 - 147 (2013/03/29)
Pristine l-proline was non-covalently loaded on the graphene oxide (GO) sheet in a simple route by mixing them in aqueous solution. Technologies of characterization well suggested that l-proline was efficiently loaded on the two sides and edge of the GO sheet through hydrogen-bonding or/and ionic interaction, giving the excellent l-proline/GO hybrid catalyst for the direct asymmetric aldol reaction. The unique multilayered structure of the GO carrier with sufficient interlayer space favored reagents' diffusion toward l-proline chiral moiety and therefore resulted in the high catalytic efficiency of the heterogeneous l-proline. Excellent yield (96%) with high enantiomeric excess (79% ee) was obtained in the direct aldol reaction of 2-nitrobenzaldehyde with acetone catalyzed by l-proline/GO hybrid, which was comparable to that observed in the reactions promoted by l-proline itself. Furthermore, the l-proline/GO hybrid used as a heterogeneous catalyst could be easily recovered and recycled for seven times without significant loss of the reactivity.
2,4-Dinitrophenol as an effective cocatalyst: Greatly improving the activities and enantioselectivities of primary amine organocatalysts for asymmetric aldol reactions
Da, Chao-Shan,Che, Li-Ping,Guo, Qi-Peng,Wu, Feng-Chun,Xiao, Ma.,Jia, Ya-Ning
experimental part, p. 2541 - 2546 (2009/08/07)
Seven primary amine organocatalysts 1a-g were readily prepared from natural primary amino acids via two steps and then were used to catalyze the direct asymmetric aldol reaction, but they showed very poor enantioselectivities and activities. As an effective cocatalyst, 2,4-dinitrophenol (DNP) dramatically elevated the activities and enantioselectivities of these very inefficient primary amine organocatalysts. This remedial course to the very inefficient organocatalysts by selection and employment of the optimal cocatalyst was particularly cost-effective and environment-beneficial compared with de novo development of catalysts. The highest efficient organocatalytic system that was composed of If and DNP showed high enantioselectivities and good to high diastereoselectivities with a broad spectrum of seven ketones. The linear ketones and cyclopentanone got predominant syn products whereas cyclohexanone mainly gave anti products.
Enamine-metal lewis acid bifunctional catalysis: Application to direct asymmetrie aldol reaction of ketones
Xu, Zhenghu,Daka, Philias,Budik, Ilya,Wang, Hong,Bai, Fu-Quan,Zhang, Hong-Xing
supporting information; experimental part, p. 4581 - 4585 (2009/12/06)
Unprecedented bifunctional enamine-metal Lewis acid, catalysts have been developed. In this bifunctional catalytic system, a tridentate ligand tethered with a chiral secondary amine was designed to solve the acid-base self-quenching problem leading to cat
Rational combination of two privileged chiral backbones: Highly efficient organocatalysts for asymmetric direct aldol reactions between aromatic aldehydes and acylic ketones
Chen, Jia-Rong,An, Xiao-Lei,Zhu, Xiao-Yu,Wang, Xu-Fan,Xiao, Wen-Jing
, p. 6006 - 6009 (2008/12/21)
(Figure Presented) A new class of organocatalysts has been designed by rational combination of proline with cinchona alkaloids. The chiral amine 3a, prepared from L-proline and cinchonidine, has been found to be an efficient catalyst for the direct aldol reactions of acetone or 2-butanone with a wide range of aldehydes (up to 98% ee). The cinchonidine backbone is essential to the reaction efficiency and enantioselectivity.
