Catalytic properties of 4,5-bridged proline methano- and ethanologues in the Hajos-Parrish intramolecular aldol reaction

The catalysis of the Hajos-Parrish reaction by cis- and trans-4,5-ethano-proline was explored experimentally and computationally with DFT (omega B97X-D and MN15) and DLPNO-CCSD(T). Both of the new catalysts are as active as proline or cis- and trans-4,5-methano-proline, with the trans-ethano-proline being as enantioselective as proline. A thorough theoretical analysis of the electronic factors influencing catalysis is reported.

Automated summary

Experimental and computational studies have shown that the new catalysts cis- and trans-4,5-ethano-proline are as active as proline or other common catalysts, with the trans-ethano-proline exhibiting high enantioselectivity. A thorough theoretical analysis of the electronic factors influencing catalysis has been reported.