The reactivity of the ITL heterocycle was studied via calculations and model reactions. The ESP mapped electron density surface of 3a and 3b are presented in Figure . Calculated at DFT/B3LYP/6-311++G(2d,p) optimization level, the electron densities of 3a and 3b clearly reflect the chemical composition of the heterocycle. The iminium carbon is particularly affected by the neighboring iminium =NH + 2 , which exhibits the lowest electron density, thus, making the carbon an ideal electrophile. This is in contrast with the corresponding thiolactone surrogates, where the areas of low electron density concentrate on the α-, β-and γcarbons of the thiolactone ring (Figure ). Depictions of the lowest unoccupied molecular orbitals (LUMO) of 3a and 3b reveal significant electron accepting properties centered around the iminium carbon (Figure ). Additionally, the molecular orbitals are largely localized around the C-S bond and show an anti-bonding character. Looking at the orbital energy levels of 3a and 3b, both LUMOs are around 1.34 eV lower than the LUMO energy levels of their respective thiolactone surrogates (Figure ). Overall, this suggests a superior electron-accepting character of ITLs, enhancing their reactivity towards nucleophiles.