The Stereochemistry of Nucleophilic Addition. II. The Reformatsky Reaction of Methyl (+)-α-Bromopropionate, 2-Phenylpropanal, and 3-Phenyl-2-butanone

The Reformatsky reaction of methyl (+)-α-bromopropionate with benzaldehyde was carried out in order to study the reaction mechanism, and two epimeric methyl 3-hydroxy-2-methyl-3-phenylpropionates (IIa and IIb) were obtained in a 59 : 41 ratio. From a comparison of the optical activity of IIb with that of pure (−)-IIb, it was estimated that lib consists only seven percent of an optically-active compound; this results supports the hypothesis of the enolate anion mechanism. Subsequently, the stereochemistry of this reaction with 2-phenyl-propanal (IV) and 3-phenyl-2-butanone (VIII) was studied. The condensation of IV with methyl bromo-acetate gave a mixture of the epimeric methyl 3-hydroxy-4-phenylvalerates (Va and Vb), which were separated in a 26 : 74 ratio by means of column chromatography on silica gel. Similarly, VIII was also condensed with methyl bromoacetate to give the epimeric methyl 3-hydroxy-3-methyl-4-phenylvalerates (IXa and IXb) in a 31 : 69 ratio. The configurations of these esters were assig...