“…Our proof-of-principle VCD studies on asymmetric catalysts have taken advantage of this conformational sensitivity and provided new insights into a variety of catalyst systems. 4 Besides examples from asymmetric counterion directed catalysis (ACDC), 9 thiourea-based hydrogen bonding organocatalysis 10 and iodane catalysis, 11 we have particularly focussed on representative examples from enamine and iminium ion catalysis: 12 In a case study on Jørgensen-Hayashi-type prolinol ether organocatalysts, 12b,13 we demonstrated that VCD spectroscopy can be used to characterize the conformational preferences of the corresponding in situ generated enamines by direct comparison of experimental and computed spectra. Likewise, for MacMillan's imidazolidinone catalyst, 14 the major conformer of the corresponding iminium ion 15 could be determined.…”