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DOI: 10.1055/sos-SD-002-00214

Kündig, E. P.; Pache, S. H.Science of Synthesis, (20032188.

Racemic complexes containing an amine or a carboxylic acid function have been resolved via formation of diastereomeric salts with chiral carboxylic acids such as (+)-camphorsulfonic acid (for ortho- and meta-toluidine complexes), or chiral amines such as brucine (for the meta-methoxybenzoic acid complex) followed by recrystallization.[‌200‌‌203‌] For ortho-substituted benzaldehyde complexes, an early resolution procedure involved formation of diastereomeric semioxamazones, separation by column chromatography, and acid hydrolysis.[‌204‌] Another very efficient procedure uses l-valinol and column chromatography on alumina to separate the diastereomeric imines formed.[‌205‌] Enzymatic kinetic resolution procedures have been used mostly in enantioselective reductions of chiral aryl aldehydes.[‌206‌‌208‌] Other examples include enzymatic ester hydrolysis,[‌209‌] and esterification reactions on benzylic alcohols[‌210‌‌212‌] and oximes.[‌213‌] Many planar chiral complexes are readi­ly resolved on commercial chiral HPLC columns.[‌214‌,‌215‌] Kinetic resolution of racemic tricarbonyl(2-chloroanisole)chromium(0) via palladium-catalyzed asymmetric alkoxycarbonylation was achieved with 30% ee.[‌216‌]

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