| Summary: | Catalysts based on (<i>R</i>, <i>R</i>)-1,2-diphenylethylenediamine are, as chiral organic catalysts, applied to the asymmetric Michael addition to <i>α</i>, <i>β</i>-unsaturated nitroalkenes under neutral conditions. The role of an aqueous medium for organic catalytic activity can be reversed concerning hydrophilic-hydrophobic function depending on the reaction conditions. In this study, to provide an environmentally friendly system, the thiourea-based catalyst substituted with 3,5-(CF<sub>3</sub>)<sub>2</sub>-Ph was used in water solvents. The hydrophobic effect of the substituent provided fast reaction, high chemical yield, and mirror-image selectivity. This reaction allowed the preparation of GABA<sub>B</sub> agonists in an optically pure manner. Additionally, GABA (<i>γ</i>-aminobutyric acid) analogs such as baclofen and phenibut were synthesized as <i>R</i>-type <i>S</i>-type with high optical purity.
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