Prolinamides versus Prolinethioamides as Recyclable Catalysts in the Enantioselective Solvent-Free Inter- and Intramolecular Aldol Reactions

✍ Scribed by Diana Almaşi; Diego A. Alonso; Carmen Nájera

• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 256 KB
• Volume: 350
• Category: Article
• ISSN: 1615-4150
• DOI: 10.1002/adsc.200800430

✦ Synopsis

Abstract

A solvent‐free asymmetric and direct anti‐aldol reaction of aliphatic ketones with aromatic aldehydes catalyzed by recyclable L‐prolineamides and L‐prolinethioamides 3 is studied. The L‐prolinethioamide 3d (5 mol%), derived from L‐Pro and (R)‐1‐aminoindane, is the most efficient catalyst for this process affording the anti‐aldol adducts in high yields with excellent diastereo‐ and enantioselectivities (up to >98/2 dr, up to 98% ee) at 0 °C or room temperature. Prolinethioamide 3d is an effective organocatalyst for the first asymmetric, solvent‐free, intramolecular Hajos–Parrish–Eder–Sauer–Wiechert reaction with comparable or higher levels of enantioselectivity (up to 88% ee) to reported catalysts in organic solvents. Moreover, organocatalyst 3d can be easily recovered and reused by a simple acid/base extraction.