Quantitative evaluation of the chloride template effect in the formation of dicationic [14]imidazoliophanes

Article abstract of DOI:10.1021/jo0262311

The formation of macrocycles containing two imidazolium rings such as 1·2X and 2·2X is anion-directed through hydrogen bonding. The template effect exerted by the chloride anion in the ring-closure reaction of the monocationic model intermediate 9⁺ to yield the [1₄]imidazoliophane 2²⁺ has been evaluated. This effect was quantified following the kinetics of the macrocyclization by using a UV-vis technique. The rate of the ring closure of monocation 9⁺ is increased up to 10 times, in the presence of Bu₄NCl 0.04 M. This finding confirms that the template effect is operative in the macrocyclization leading to dicationic [1₄]imidazoliophanes.