کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5219174 | 1383350 | 2012 | 6 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Solvent-free asymmetric aldol reaction organocatalyzed by (S)-proline-containing thiodipeptides under ball-milling conditions Solvent-free asymmetric aldol reaction organocatalyzed by (S)-proline-containing thiodipeptides under ball-milling conditions](/preview/png/5219174.png)
An efficient, solvent-free ball-milling protocol for the asymmetric aldol reaction between cyclohexanone and cyclopentanone with various aromatic aldehydes using a novel series of (S)-proline-containing dipeptides and thiodipeptides 1a-f as organocatalysts is reported. In general, (S)-proline-containing thiodipeptides proved to be better organocatalysts relative to their analogous amides. In particular, thiodipeptide (S,S)-1d catalyzed the stereoselective formation of the expected aldol products with excellent diastereo- and enantioselectivity (up to 98:2 anti/syn dr and up to 96% ee). This observation may be ascribed to the increased N-H acidity of the thioamide segment that leads to stronger H-bonding interaction with the aldehyde carbonyl at the transition state and thus higher stereoinduction. Furthermore, thiodipeptide 1f proved to be an efficient organocatalyst for the aldol reaction of acetone with isatin and isatin derivatives (ee 56-86%).
Journal: Tetrahedron - Volume 68, Issue 1, 7 January 2012, Pages 92-97