Enantioselective Synthesis of Dihydrofurans Using Dynamic Kinetic Resolution

Significance

The synthesis of dihydrofurans via a dynamic kinetic asymmetric domino oxa-Michael-carbocyclization procedure is reported. The optimization of the reaction parameters (solvent, temperature, metal source, additives, organocatalyst) is described. The requirements for both a metal catalyst and a proline-derived organocatalyst for the transformation were established. Although aryl substitution in the aldehyde component was well tolerated, aliphatic aldehydes were found to give lower yields. The use of secondary and tertiary propargylic alcohols was also shown to afford good enantioselectivity, but poor diastereoselectivity.