2,4-Dinitrophenol as an Effective Cocatalyst: Greatly Improving the Activities and Enantioselectivities of Primary Amine Organocatalysts for Asymmetric Aldol Reactions

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) dramat...

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Bibliographic Details
Published in:Journal of organic chemistry 2009-03, Vol.74 (6), p.2541-2546
Main Authors: Da, Chao-Shan, Che, Li-Ping, Guo, Qi-Peng, Wu, Feng-Chun, Xiao Ma, Jia, Ya-Ning
Format: Article
Language:English
Subjects:
2,4-Dinitrophenol - chemistry
Alcohols - chemistry
Aldehydes - chemistry
Alicyclic compounds
Alicyclic compounds, terpenoids, prostaglandins, steroids
Amines - chemistry
Catalysis
Catalysts: preparations and properties
Chemistry
Cyclohexanones
Cyclopentanes
Exact sciences and technology
General and physical chemistry
Ketones
Organic chemistry
Preparations and properties
Stereoisomerism
Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
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Summary: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 1f 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.
ISSN:0022-3263
1520-6904
DOI:10.1021/jo802758b