Tiefel, Anna F. and Grenda, Daniel J. and Allacher, Carina and Harrer, Elias and Nagel, Carolin H. and Kutta, Roger J. and Hernandez-Castillo, David and Narasimhamurthy, Poorva R. and Zeitler, Kirsten and Gonzalez, Leticia and Rehbein, Julia and Nuernberger, Patrick and Breder, Alexander (2024) Unimolecular net heterolysis of symmetric and homopolar σ-bonds. NATURE, 632 (8025). 550-+. ISSN 0028-0836, 1476-4687
Full text not available from this repository. (Request a copy)Abstract
The unimolecular heterolysis of covalent sigma-bonds is integral to many chemical transformations, including S(N)1-, E1- and 1,2-migration reactions. To a first approximation, the unequal redistribution of electron density during bond heterolysis is governed by the difference in polarity of the two departing bonding partners(1-3). This means that if a sigma-bond consists of two identical groups (that is, symmetric sigma-bonds), its unimolecular fission from the S-0, S-1, or T-1 states only occurs homolytically after thermal or photochemical activation(1-7). To force symmetric sigma-bonds into heterolytic manifolds, co-activation by bimolecular noncovalent interactions is necessary(4). These tactics are only applicable to sigma-bond constituents susceptible to such polarizing effects, and often suffer from inefficient chemoselectivity in polyfunctional molecules. Here we report the net heterolysis of symmetric and homopolar sigma-bonds (that is, those with similar electronegativity and equal leaving group ability(3)) by means of stimulated doublet-doublet electron transfer (SDET). As exemplified by Se-Se and C-Se sigma-bonds, symmetric and homopolar bonds initially undergo thermal homolysis, followed by photochemically SDET, eventually leading to net heterolysis. Two key factors make this process feasible and synthetically valuable: (1) photoexcitation probably occurs in only one of the incipient radical pair members, thus leading to coincidental symmetry breaking(8) and consequently net heterolysis even of symmetric sigma-bonds. (2) If non-identical radicals are formed, each radical may be excited at different wavelengths, thus rendering the net heterolysis highly chemospecific and orthogonal to conventional heterolyses. This feature is demonstrated in a series of atypical S(N)1 reactions, in which selenides show SDET-induced nucleofugalities(3) rivalling those of more electronegative halides or diazoniums.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | S(N)1 IONIC DISSOCIATION; THEORETICAL-MODEL; ABSORPTION; ACTIVATION; SPECTRA; |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Organische Chemie Chemistry and Pharmacy > Institut für Organische Chemie > Arbeitskreis Prof. Dr. Alexander Breder Chemistry and Pharmacy > Institut für Physikalische und Theoretische Chemie |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 17 Jul 2025 10:29 |
| Last Modified: | 17 Jul 2025 10:29 |
| URI: | https://pred.uni-regensburg.de/id/eprint/63559 |
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