Temperature and Solvent Effect on the Nucleophilic Addition of n-Butyllithium to the N-(Trimethylsilyl)imine of (2S)-Lactal

✍ Scribed by Prof. Dr. Gianfranco Cainelli; Dr. Daria Giacomini; Dr. Martin Walzl

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 342 KB
• Volume: 34
• Category: Article
• ISSN: 0044-8249
• DOI: 10.1002/anie.199521501

✦ Synopsis

Are the Felkin–Ahn and Cram chelate models reliable? These models predict asymmetric induction without consideration of solvent and temperature. However, the addition of n‐butyllithium to the N‐(trimethylsily)imine of (2__S__)‐lactal leads to syn/anti ratios between 98:2 and 28:72 when performed in different solvents and at different temperatures. The reaction appears to be the first example of nucleophilic addition that follows the isoinversion principle (isoinversion temperature T~i~ = −21 °C). This indicates a stepwise process with at least two diastereoselective steps that are affected differently by temperature and solvent.