4-Bromobenzaldehyde: Benzaldehyde, 4-bromo

The crude product (Note 2) is transferred to a 2-I. flask and mixed thoroughly with 200 g. of powdered calcium carbonate. About 300 cc. of water is added and the mixture is heated cautiously (Note 3) and then refluxed for fifteen hours to effect hydrolysis. The product is then distilled in a rapid current of steam (Note 4), and the distillate is collected in soo-cc. portions, cooled, and the />-bromobenzaldehyde is collected and dried in a desiccator. From the first liter of distillate 50-60 g. of -bromo-benzaldehyde melting at 55-57° is obtained. An additional... 

Benzaldehyde, 3-bromo- Benzaldehyde, m-bromo- 3-Bromobenzaldehyde m-Bromobenzaldehyde EINECS 221-526-9 NSC 66828. Liquid bp = 234° Xm = 245, 291 nm (s = 6500, 790, MeOH) insoluble in H2O, slightly soluble in CCI4, very soluble in EtOH, Et20. 

The enzymes benzaldehyde lyase (BAL) and benzoylformate decarboxylase (BFD) have also been shown to catalyze enantioselective cross-benzoin reactions. Aryl-aryl as well as aryl-alkyl products are produced in high yield and enantiomeric purity. In the case of aryl-aryl products, the success of the reaction depends on the empirical identification of suitable donor/acceptor pairs. Aldehydes containing or/Ao-substituents were found to be ideal acceptors in BAL and BFD-catalyzed cross-benzoin reactions. The preparation of (/ )-l-(4-bromophenyl)-2-(2-chlorophenyl)-2-hydroxyethanone (25) from 4-bromobenzaldehyde (23) and 2-chlorobenzaldehyde (24) highlights the high conversion and selectivity possible in this transformation. As with rac-benzoin, rac-l-(4-bromo-phenyl)-2-(2-chlorophenyl)-2-hydroxyethanone is easily resolved by BAL to give the (5)-enantiomer with high enantiomeric purity. 

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