Constrained β-Proline Analogues in Organocatalytic Aldol Reactions: The Influence of Acid Geometry

详细信息    查看全文

• 作者：Alan Armstrong ; Yunas Bhonoah ; Andrew J. P. White
• 刊名：Journal of Organic Chemistry
• 出版年：2009
• 出版时间：July 17, 2009
• 年：2009
• 卷：74
• 期：14
• 页码：5041-5048
• 全文大小：372K
• 年卷期：v.74,no.14(July 17, 2009)
• ISSN：1520-6904

文摘

7-Azabicyclo[2.2.1]heptane-2-carboxylic acid 11 was prepared in enantiopure form, and its catalytic potential in the direct aldol reaction between acetone and 4-nitrobenzaldehyde was assessed. The bicyclic system was found to be more selective than its monocyclic analogue β-proline 5b. A comparative density functional theory study of proline 1, β-proline 5b, and 11 in the latter reaction revealed the origin of the improved enantioselectivity of 11 over 5b. The geometry of the carboxylic acid group in the transition states, which depended critically on pyrrolidine ring conformation, was found to play a key role.