Disclosing Cyclic(Alkyl)(Amino)Carbenes as One-Electron Reductants: Synthesis of Acyclic(Amino)(Aryl)Carbene-Based Kekulé Diradicaloids

Avijit Maiti; Benedict J Elvers; Sachinath Bera; Felix Lindl; Ivo Krummenacher; Prasanta Ghosh; Holger Braunschweig; Cem B Yildiz; Carola Schulzke; Anukul Jana

doi:10.1002/chem.202104567

Disclosing Cyclic(Alkyl)(Amino)Carbenes as One-Electron Reductants: Synthesis of Acyclic(Amino)(Aryl)Carbene-Based Kekulé Diradicaloids

Chemistry. 2022 May 16;28(28):e202104567. doi: 10.1002/chem.202104567. Epub 2022 Apr 19.

Authors

Affiliations

¹ Tata Institute of Fundamental Research Hyderabad Gopanpally, Hyderabad, 500046, Telangana, India.
² Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Straße 4, 17489, Greifswald, Germany.
³ Department of Chemistry, Ramakrishna Mission Residential College Narendrapur, Kolkata, 700103, India.
⁴ Shahid Matangini Hazra Govt General Degree College for Women Tamluk, Purba Medinipur, 721649, India.
⁵ Institute of Inorganic Chemistry and Institute for Sustainable Chemistry & Catalysis with Boron (ICB), Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany.
⁶ Department of Aromatic and Medicinal Plants, Aksaray University, Aksaray, 68100, Turkey.

Abstract

Herein, we disclose cyclic(alkyl)(amino)carbenes (CAACs) to be one-electron reductants under the formation of a transient radical cation as indicated by EPR spectroscopy. The disclosed CAAC reducing reactivity was used to synthesize acyclic(amino)(aryl)carbene-based Thiele and Chichibabin hydrocarbons, a new class of Kekulé diradicaloids. The results demonstrate CAACs to be potent organic reductants. Notably, the acyclic(amino)(aryl)carbene-based Chichibabin's hydrocarbon shows an appreciable population of the triplet state at room temperature, as evidenced by both variable-temperature NMR and EPR spectroscopy.

Keywords: EPR spectroscopy; carbene; electrochemistry; radical cation; reductant.