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) 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.
Da
Chao-Shan
CS
Institute of Biochemistry & Molecular Biology, School of Life Sciences, Lanzhou University, Lanzhou 730000, China. dachaoshan@lzu.edu.cn
Che
Li-Ping
LP
Guo
Qi-Peng
QP
Wu
Feng-Chun
FC
Xiao Ma
Jia
Ya-Ning
YN
D019297:2,4-Dinitrophenol / Q000737:chemistry*; D000438:Alcohols / Q000737:chemistry*; D000447:Aldehydes / Q000737:chemistry*; D000588:Amines / Q000737:chemistry*; D002384:Catalysis; D003512:Cyclohexanones; D003517:Cyclopentanes; D007659:Ketones; D013237:Stereoisomerism
D000438:Alcohols; D000447:Aldehydes; D000588:Amines; D003512:Cyclohexanones; D003517:Cyclopentanes; D007659:Ketones; C007201:cyclopentanone; C036468:cyclohexanone; D019297:2,4-Dinitrophenol