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Understanding the Nonlinear Hammett Relationship in Osmylation of Olefins with OsO 4 -Amine Ligands: Importance of Singlet-Diradical Character.
- Source :
-
The Journal of organic chemistry [J Org Chem] 2024 Aug 16; Vol. 89 (16), pp. 11173-11182. Date of Electronic Publication: 2024 Jul 29. - Publication Year :
- 2024
-
Abstract
- Although the concerted [3 + 2] mechanism of osmium-catalyzed asymmetric dihydroxylation has been generally accepted, the unusual nonlinear Hammett relationship induced by amine-type ligands remains unexplained. To understand this, we carried out a density functional theory (DFT) study for the osmylation of substituted styrenes by the following: OsO <subscript>4</subscript> , OsO <subscript>4</subscript> -pyridine, OsO <subscript>4</subscript> -4-cyanopyridine, OsO <subscript>4</subscript> -4-pyrrolidinopyridine, and OsO <subscript>4</subscript> -quinuclidine. Calculations using the M06 functional successfully reproduce the experimentally observed nonlinear relationships. The transition states exhibit considerable singlet-diradical character, which causes the nonlinear Hammett relationship. Regardless of the presence or absence of an amine-type ligand, an electron donation from styrene to OsO <subscript>4</subscript> is observed, indicating no mechanistic change. Calculations indicate that the electronic interaction between the amine-type ligand and styrene also influences the reaction rate.
Details
- Language :
- English
- ISSN :
- 1520-6904
- Volume :
- 89
- Issue :
- 16
- Database :
- MEDLINE
- Journal :
- The Journal of organic chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 39072554
- Full Text :
- https://doi.org/10.1021/acs.joc.4c00693