Optical Resolution ofα-Bromo-2-Chlorophenacetic Acid by Way of Coordination with Copper(II) and O,O’-Dibenzoyltartaric Acid

Optically active molecules play important roles in medicinal chemistry and materials science in both industrial and academic sectors. Resolution is one of the most efficient ways to obtain enantiopure substances. For a long period, racemic carboxylic acids are generally resolved by optically active bases, however, these bases are often extremely toxic and expensive.1] Recently, A. Mravik Group applied optically active O, O’-dibenzoyltartaric acid (DBTA), which is usually used for the res…

Optical Resolution of α-Bromo-2-Chlorophenacetic Acid by Way of Coordination with Copper(Ⅱ) and O,O'-Dibenzoyltartaric Acid

Optically active molecules play important roles in medicinal chemistry and materials science in both industrial and academic sectors. Resolution is one of the most efficient ways to obtain enantiopure substances. For a long period, racemic carboxylic acids are generally resolved by optically active bases, however, these bases are often extremely toxic and expensive.1] Recently, A.Mravik Group applied optically active O, O'-dibenzoyltartaric acid (DBTA), which is usually used for the resolution of bases, as a new resolving reagent for the racemic carboxylic acids. Some new metal co-complexes of DBTA can form with the racemic acids and then optically active acids can be obtained by decomposition of the resulting salts. 2] In contrast, optically pure DBTA is relatively cheap, nontoxic reagent. Therefore, this method will be a promising one for the resolution of acids.In many traditional resolutions, the theoretic maximum yield for each of the two pure enantiomers cannot exceed 50%. So scientists were interested in the resolution in which there is an epimerization process owing to the fact that the theoretic yield of one of the two pure enantiomers may be greater than 50%. Asymmetric transformation is one of such cases.Herein, we report a resolution procedure in which α-bromo-2-chlorophenacetic acid was resolved efficiently by way of coordination with copper(Ⅱ) salt and commercially available optically active DBTA. Asymmetric transformation of α -bromo-2-chlorophenacetic acid was found in this resolution procedure, in which 84% yield based on the racemic acid was obtained with 94%enantiomeric excess of the acid (See Scheme 1).