Hydrogen‐Bonding Thiourea Organocatalysts: The Privileged 3,5‐Bis(trifluoromethyl)phenyl Group

We present evidence that the privileged use of the 3,5‐bis(trifluoromethyl)phenyl group in thiourea organocatalysis is due to the involvement of the ortho ‐CH bond in the binding event with Lewis‐basic sites. We utilized a combination of low‐temperature IR spectroscopy, 2D NMR spectroscopy, nano‐MS (ESI) investigations, as well as density functional theory computations [M06/6‐31+G( d , p ), including solvent corrections as well as natural bond orbital and atoms‐in‐molecules analyses] to support our conclusions that bear implications for catalyst design.