Evidence of AlII Radical Addition to Benzene. (17th February 2023)

• Record Type: Journal Article
• Authors: Mandal, Debdeep; Demirer, T. Ilgin; Sergeieva, Tetiana; Morgenstern, Bernd; Wiedemann, Haakon T. A.; Kay, Christopher W. M.; Andrada, Diego M.
• Is Part Of: Angewandte Chemie. Volume 135:Number 13(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-02-17
• Subjects: Aluminum -- EPR Spectroscopy -- Low-Valent Compounds -- Radicals -- Structure Elucidation; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.202217184
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: Electrophilic Al III species have long dominated the aluminum reactivity towards arenes. Recently, nucleophilic low‐valent Al I aluminyl anions have showcased oxidative additions towards arenes C−C and/or C−H bonds. Herein, we communicate compelling evidence of an Al II radical addition reaction to the benzene ring. The electron reduction of a ligand stabilized precursor with KC8 in benzene furnishes a double addition to the benzene ring instead of a C−H bond activation, producing the corresponding cyclohexa‐1, 3(orl, 4)‐dienes as Birch‐type reduction product. X‐ray crystallographic analysis, EPR spectroscopy, and DFT results suggest this reactivity proceeds through a stable Al II radical intermediate, whose stability is a consequence of a rigid scaffold in combination with strong steric protection. Abstract : The electron reduction of diamido‐naphthyl aluminum iodide in benzene produces dialuminyl substituted Birch‐type reduction product. Time dependent EPR experiments in combination with DFT calculations suggest a reaction mechanism where stable Al II radical intermediates play a crucial role for the reaction outcome. The aluminum radical stability is a consequence of a rigid supporting ligand with silyl protective substituents.