Separation of the Thorpe−Ingold and Reactive Rotamer Effect by Using the Formation of Bicyclic Aziridinium Ions

Abstract The geminal dialkyl effect is widely used in organic synthesis to promote cyclization reactions, although the exact origin of its rate enhancement remains unclear. In present study, we demonstrate applicability this for intramolecular formation bicyclic aziridinium ions and assign it angle contractions provided by introduction sterically demanding substituents. Due cyclic structure examined 3‐chloropiperidines acceleration ring closure cannot be explained an increased population reactive gauche rotamers therefore agrees with original Thorpe‐Ingold theory. Furthermore, strained aliphatic rings resulted internal expansions were accompanied a preliminary decrease constants investigated ion formation. These results lead linear correlation between relative reaction rate, supported computational X‐ray crystallographic structural data.