Preparation, Isolation,\nand Structural Characterization\nof Lewis Base Iminium Salts of 1,8-Diazabicyclo[5.4.0]undec-7-ene\nand Their Application as Green Reagents in an Aqueous Medium

We report a state-of-the-art synthesis and isolation\nprocedure\nfor 13 Lewis base iminium salts (LBI) of 1,8-diazabicyclo[5.4.0]undec-7-ene\n(DBU), confirming their structures meticulously by different spectral\ndata. The LBIs are distinct from their parent compound (DBU), which\nprovides emphatic support in favor of LBI formation in various DBU-catalyzed\nreactions. Density functional theory studies of N-sulfonyl LBI of\nDBU have given new insight into alternate iminium salts, offering\na new opportunity for further investigation. We describe the applications\nof three LBIs as direct reagents for base-free functionalization,\nbroadening their scope as eco-friendly reagents in aquatic media.\nThe Lewis base is recoverable and reusable to prepare the LBI after\nthe reaction. We also document the influence of the N substituent\non the chemical shift of these iminium salts.