A joint experimental, in silico and NMR studies towards the rational design of iminium-based organocatalyst derived from renewable sources

Abstract

An efficient organocatalyst for iminium-ionbased asymmetric Diels−Alder (DA) reactions has beenrationally designed. The most influential structure−activityrelationships were determined experimentally, while DFTcalculations and NMR studies provided further mechanisticinsight. This knowledge guided an in silico screening of 62different catalysts using an ONIOM(B3LYP/6-31G*:AM1)transition-state modeling, which showed good correlationbetween theory and experiment. The top-scored compoundwas easily synthesized from levoglucosenone, a biomass-derived chiral enone, and evaluated in the DA reaction between (E)-cinnamaldehyde and cyclopentadiene. In line with the computational finding, excellent results (up to 97% ee) were obtained. Inaddition, the catalyst could be easily recovered and reused with no loss in its catalytic activity.