Encouraged by these results, we set out to synthesize 1, which possesses NHC and CDI components not previously reported in the literature (Figure ). First, we sought to optimize the synthesis of NHC-CDIs based on sterically unencumbered NHCs using the previously reported naphthyl imidazolium salt 2 as a model; 20-21 however, attempts to kinetically trap the NHC by deprotonation of 2 in the presence of excess 18 3 were unsuccessful, yielding only NHC dimer 4. While this kinetic approach failed, we hypothesized that the thermal reversibility of 4 at elevated temperatures, and the anticipated stability of the NHC-CDI adduct, could enable an alternative thermodynamic approach. Indeed, after optimization, exposing NHC dimer 4 to CDI 3 at 120 °C for 4 h cleanly afforded the target NHC-CDI 5 in quantitative yield. Single crystal X-ray diffraction (XRD) confirmed the structure of 5 as the Z/Z isomer in the solid state. With this new synthetic route to NHC-CDI adducts in hand, we turned our attention to the synthesis of the 3,4,5trimethoxy imidazolium salt (6). Due to the ubiquitous use of NHCs as organocatalysts or ancillary ligands in transition-metal catalysis, it was surprising that 6 has not previously been reported. Attempts to follow standard synthetic approaches toward 6 initially proved unsuccessful. After various attempts, we found that the synthesis could be accomplished by adapting an earlier reported procedure by Grubbs and coworkers. The key modification was the addition of DMF as a non-nucleophilic, polar cosolvent in the ring-closing reaction between the formimide intermediate and DCE, as the 3,4,5-trimethoxy formimide proved insoluble in DCE even at 160 °C. With 6 in hand, the corresponding NHC dimer 7 was readily prepared via deprotonation with KHMDS. Gratifyingly, compound 1 was obtained in 94 % yield following an analogous procedure to that used to synthesize 5. Single crystal XRD analysis of 1 validated our structural assignment, but to our surprise, 1 adopted the Z/Z conformation in the solid state. Further calculations identified significant packing effects (for example intermolecular CH-p interactions) that favor the Z/Z conformation in the solid state (SI Table ). To compare these sterically unencumbered NHC-CDIs to their sterically encumbered analogs, two NHC-CDI adducts with NHC containing the N-aryl groups 2,6-Me-6-BrC6H2 ( ) and 2,6-I PrC6H3 (9) were synthesized. Single crystal XRD of 8 and 9 identified that they also form the Z/Z isomers in the solid state.