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

Swathi Thangalipalli; Siddaramagoud Bandalla; Nagaraju Kerru; Jhansi Rani Vadala; Chandra Sekhar Vasam; Chandra Kiran Neella; Sreekantha B Jonnalagadda

doi:10.1021/acsomega.4c05896

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

ACS Omega. 2024 Nov 21;9(49):48285-48291. doi: 10.1021/acsomega.4c05896. eCollection 2024 Dec 10.

Authors

Swathi Thangalipalli¹, Siddaramagoud Bandalla^{2

3}, Nagaraju Kerru⁴, Jhansi Rani Vadala⁵, Chandra Sekhar Vasam³, Chandra Kiran Neella¹, Sreekantha B Jonnalagadda⁴

Affiliations

¹ Department of Chemistry, Palamuru University, Mahbubnagar, Telangana 509001, India.
² Department of Integrated Chemistry, Palamuru University, Mahbubnagar, Telangana 509001, India.
³ Department of Pharmaceutical Chemistry, Telangana University, Nizamabad 503322, India.
⁴ School of Chemistry & Physics, University of KwaZulu-Natal, Durban 4000, South Africa.
⁵ School of Chemistry, University of Hyderabad, Hyderabad 500046, India.

Abstract

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