Organocatalytic transfer hydrogenation of cyclic enones.
The first enantioselective organocatalytic transfer hydrogenation of cyclic enones has been accomplished. The use of iminium catalysis has provided a new organocatalytic strategy for the enantioselective reduction of beta,beta-substituted alpha,beta-unsaturated cycloalkenones, to generate beta-stereogenic cyclic ketones. The use of imidazolidinone 4 as the asymmetric catalyst has been found to mediate the hydrogenation of a large class of enone substrates with tert-butyl Hantzsch ester serving as an inexpensive source of hydrogen. The capacity of catalyst 4 to enable enantioselective transfer hydrogenation of cycloalkenones has been extended to five-, six-, and seven-membered ring systems. The sense of asymmetric induction is in complete accord with the stereochemical model first reported in conjunction with the use of catalyst 4 for enantioselective ketone Diels-Alder reactions.
Tuttle
Jamison B
JB
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
Ouellet
Stéphane G
SG
MacMillan
David W C
DW
D002384:Catalysis; D003516:Cycloparaffins / Q000737:chemistry*; D006844:Hydrocarbons, Cyclic / Q000138:chemical synthesis* / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D007659:Ketones / Q000138:chemical synthesis* / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D013237:Stereoisomerism
D003516:Cycloparaffins; D006844:Hydrocarbons, Cyclic; D007659:Ketones; D006859:Hydrogen