Study of the Mechanism of Optical Resolutions Via Diastereoisomeric Salt Formation Part 4. The Role of the Crystallization Temperature in Optical Resolution of Pipecolic Acid Xylidides

The role of the crystallization temperature was investigated during the optical resolutions of some pipecolic acid xylides by 2R,3R-tartaric acid and O,O-dibenzoyl-2R/3R-tartaric acid. In 4 cases from 5 the temperature optimum of the crystallization was found between 45-50 degrees C, which is much higher than the usual crystallization temperature. A few trial resolutions may be enough to determine the temperature optimum of the crystallization graphically.