Bánhegyi, D.F.; Fogassy, E.; Pálovics, E. Possibilities of Exploiting Kinetic Control in the Continuous Fractional Crystallization of Diastereomeric Mixtures. Symmetry 2021*, 13, 1516.*

We dissolved 5 g of the racemic compound (2-phenyl-1methyl)-ethylamine in a mixture of 12 cm3 of IPA and 1.53 cm3 of aqueous hydrochloric acid (37%), which was heated to boiling. Then, 2.81 g (—)-tartaric acid was added to the hot mixture. The obtained diastereomeric salt was filtrated quickly* and washed with 2 x 4 cm3 of IPA. The obtained salt was suspended with 10 cm3 of hexane, filtrated, and then dried on air. The weight of the obtained salt was 4.62 g (87.5%), [a]20D = -25.3 (c = 1, water), and ee: 83.5%. The diastereomeric salt obtained was suspended in a solution of 11 cm3 of IPA and 0.3 cm3 of diluted hydrochloride acid (37%) while stirring and heating to boil twice (the diastereomeric salt remained in suspension). The mixture was cooled to 30C in 10 min. The obtained salt was suspended with 10 cm3 of hexane, filtrated, and dried on air. The weight of the obtained salt was 3.7 g (70.0%), [a]20D = —28.8 (c = 1, water), and ee: 95%.

See also Rapid deracemization through solvent cycling: proof-of-concept using a racemizable conglomerate clopidogrel precursor" Chemical Communications 2023, 59, 3838.