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Steiner L, Achazi AJ, Kelterer AM, Paulus B, Reissig HU. Diastereoselective Dearomatizing Cyclizations of 5-Arylpentan-2-ones by Samarium Diiodide - A Computational Analysis. Chemistry 2024; 30:e202401120. [PMID: 38512639 DOI: 10.1002/chem.202401120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2024] [Accepted: 03/21/2024] [Indexed: 03/23/2024]
Abstract
This study analyzes the samarium diiodide-promoted cyclizations of 5-arylpentan-2-ones to dearomatized bicyclic products utilizing density functional theory. The reaction involves a single electron transfer to the carbonyl group, which occurs synchronously with the rate determining cyclization event, and a second subsequent proton-coupled electron transfer. These redox reactions are accurately computed employing small core pseudo potentials explicitly involving all f-electrons of samarium. Comparison of the energies of the possible final products rules out thermodynamic control of the observed regio- and diastereoselectivities. Kinetic control via appropriate transition states is correctly predicted, but to obtain reasonable energy levels the influence of the co-solvent hexamethylphosphortriamide has to be estimated by using a correction term. The steric effect of the bulky samarium ligands is decisive for the observed stereoselectivity. Carbonyl groups in para-position of the aryl group change the regioselectivity of the cyclization and lead to spiro compounds. The computations suggest again kinetic control of this deviating outcome. However, the standard mechanism has to be modified and the involvement of a complex activated by two SmI2 moieties is proposed in which two electrons are transferred simultaneously to form the new C-C bond. Computation of model intermediates show the feasibility of this alternative+ mechanism.
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Affiliation(s)
- Luca Steiner
- Institut für Chemie und Biochemie, Freie Universität Berlin, Arnimallee 22, 14195, Berlin, Germany
- Institut für Physikalische und Theoretischen Chemie, Technische Universität Graz, Stremayrgasse 9, 8010, Graz, Austria
| | - Andreas J Achazi
- Physikalisch-Chemisches Institut, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 17, 35392, Gießen, Germany
- Zentrum für Materialforschung, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 16, 35392, Gießen, Germany
| | - Anne-Marie Kelterer
- Institut für Physikalische und Theoretischen Chemie, Technische Universität Graz, Stremayrgasse 9, 8010, Graz, Austria
| | - Beate Paulus
- Institut für Chemie und Biochemie, Freie Universität Berlin, Arnimallee 22, 14195, Berlin, Germany
| | - Hans-Ulrich Reissig
- Institut für Chemie und Biochemie, Freie Universität Berlin, Arnimallee 22, 14195, Berlin, Germany
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Schwans CL, Clark TD, O’Neil GW. Hydroxyl-Directed Regio- and Diastereoselective Allylic Sulfone Reductions with [Sm(H 2O) n]I 2. J Org Chem 2024; 89:692-700. [PMID: 38091512 PMCID: PMC10777405 DOI: 10.1021/acs.joc.3c01647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 11/19/2023] [Accepted: 11/21/2023] [Indexed: 01/06/2024]
Abstract
Allylic 1,2- and 1,3-hydroxy phenyl sulfones undergo regioselective and diastereoselective desulfonylation with double bond migration upon treatment with [Sm(H2O)n]I2. Selectivity in these reactions is thought to arise from the formation of a chelated organosamarium intermediate followed by intramolecular protonation by samarium-bound water, which is supported by observed diastereoselectivity and stereospecificity trends along with deuterium labeling experiments. The reaction was then featured in the synthesis of the phenolic fragment of the thailandamide natural products.
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Affiliation(s)
- Cody L. Schwans
- Department of Chemistry, Western Washington University, Bellingham, Washington 98225, United States
| | - Trevor D. Clark
- Department of Chemistry, Western Washington University, Bellingham, Washington 98225, United States
| | - Gregory W. O’Neil
- Department of Chemistry, Western Washington University, Bellingham, Washington 98225, United States
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