Asymmetric Direct Aldol Reaction Catalyzed by (1R, 2R)-(+)-1, 2- Diammonium Cyclohexane-L-tartrate in Water

Abstract

Background: A cheap and commercially available organocatalyst, (1R, 2R)-(+)-1, 2- diammonium cyclohexane-L-tartrate 1 was applied in direct aldol reaction in water. The organocatalyst 1 afforded aldol products from cyclohexanone and substituted aromatic aldehydes with high yield (up to 90%) and good stereoselectivity (up to 99% ee and up to 11.5:1 dr) in large volume of water (10 ml). Methods: The same aldol reaction when carried out in the presence of more expensive organocatalyst e.g. (1R, 2R)-(+)-1,2-diaminocyclohexane and 1,6-hexanediaoic acid as acid additive furnished the aldol products with only 20% yield, 2:1 anti/syn ratio and 92% ee. Results and Conclusion: In summary, we have applied a reasonably cheap and commercially available organocatalyst 1 for highly enantioselective direct aldol reaction in water at room temperature.