A highly efficient organocatalyst for direct aldol reactions of ketones with aldehydes [corrected].
L-proline amides derived from various chiral beta-amino alcohols that bear substituents with various electron natures at their stereogenic centers are prepared and evaluated for catalyzing the direct Aldol reaction of 4-nitrobenzaldehyde with acetone. Catalysts with strong electron-withdrawing groups are found to exhibit higher catalytic activity and enantioselectivity than their analogues with electron-donating groups. The presence of 2 mol % catalyst 4g significantly catalyzes the direct Aldol reactions of a wide range of aldehydes with acetone and butanone, to give the beta-hydroxy ketones with very high enantioselectivities ranging from 96% to >99% ee. High diastereoselectivity of 95/5 was observed for the anti Aldol product from the reaction of cyclohexanone, and excellent enantioselectivity of 93% ee was provided for anti Aldol product from the reaction of cyclopentanone.
Tang
Zhuo
Z
Key Laboratory for Asymmetric Synthesis and Chirotechnology of Sichuan Province, Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu, 610041, China.
Yang
Zhi-Hua
ZH
Chen
Xiao-Hua
XH
Cun
Lin-Feng
LF
Mi
Ai-Qiao
AQ
Jiang
Yao-Zhong
YZ
Gong
Liu-Zhu
LZ
D000447:Aldehydes / Q000138:chemical synthesis* / Q000737:chemistry; D000577:Amides / Q000737:chemistry*; D002384:Catalysis; D007659:Ketones / Q000138:chemical synthesis* / Q000737:chemistry; D008968:Molecular Conformation; D011392:Proline / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000737:chemistry*; D013237:Stereoisomerism
D000447:Aldehydes; D000577:Amides; D007659:Ketones; D011392:Proline