Effect of basic and acidic additives on the (S)-proline and Pd mediated kinetic resolution of 3,5,5-trimethyl cyclohexanone and asymmetric hydrogenation of isophorone

The kinetic resolution of 3,5,5-trimethyl cyclohexanone (TMCH) and the asymmetric hydrogenation of isophorone (IP) were investigated both in the presence of (S)-proline (Pro) and of basic and acidic additives. The aim was to find out how the bidirectional shift from the zwitterionic form of proline can influence the reaction rates and stereoselectivities of these reactions.

Graphical abstractThe kinetic resolution of 3,5,5-trimethyl cyclohexanone (TMCH) and the asymmetric hydrogenation of isophorone (IP) were investigated both in the presence of (S)-proline (Pr) and of basic and acidic additives.Figure optionsDownload full-size imageDownload high-quality image (63 K)Download as PowerPoint slideResearch highlights▶ Acids increased reaction rate but decreased selectivity in kinetic resolution. ▶ Triethyl amine increased rate and selectivity as well. ▶ Both acids and bases decreased enantioselectivity in isophorone hydrogenation. ▶ The neutral medium was necessary for the direct asymmetric CC hydrogenation.