Advances in [1,2]-Sigmatropic Rearrangements of Onium Ylides via Carbene Transfer Reactions

This review article summarizes progress made in [1,2]-sigmatropic rearrangements using carbenes in the ylide formation step. While other rearrangements, such as the [2,3]-sigmatropic, Doyle-Kirmse, or Sommelet-Hauser rearrangements, have been studied in detail over the past decades, studies on [1,2]-sigmatropic rearrangements are still limited. Based on the application of diazoalkanes as carbene precursors, research on diazoalkanes in ylide formation reactions started flourishing in the 1990s. This review covers milestones from the beginning of [1,2]-sigmatropic rearrangements using carbenes to generate ammonium, oxonium and other ylide species and should serve as an overview to further promote research in this area.

Melding of Experiment and Theory Illuminates Mechanisms of Metal-Catalyzed Rearrangements: Computational Approaches and Caveats

This review summarizes approaches and caveats in computational modeling of transition-metal-catalyzed sigmatropic rearrangements involving carbene transfer. We highlight contemporary examples of combined synthetic and theoretical investigations that showcase the synergy achievable by integrating experiment and theory.1 Introduction2 Mechanistic Models3 Theoretical Approaches and Caveats3.1 Recommended Computational Tools3.2 Choice of Functional and Basis Set3.3 Conformations and Ligand-Binding Modes3.4 Solvation4 Synergy of Experiment and Theory – Case Studies4.1 Metal-Bound or Free Ylides?4.2 Conformations and Ligand-Binding Modes of Paddlewheel Complexes4.3 No Metal, Just Light4.4 How To ‘Cope’ with Nonstatistical Dynamic Effects5 Outlook

Synthesis and [3,3]-sigmatropic rearrangements of 5-(pentafluorosulfanyl)-pent-3-en-2-ol, its homologues, and trifluoromethyl analogues

The synthesis of aliphatic (pentafluoro-λ6-sulfanyl)(SF5)-substituted compounds is more challenging than that of the related CF3-substituted analogues. Previous investigations of [3,3]-sigmatropic rearrangements of γ-SF5-substituted allylic alcohols failed to yield 3-SF5-substituted carboxylic...

Metal-Bound or Free Ylides as Reaction Intermediates in Metal-Catalyzed [2,3]-Sigmatropic Rearrangements? It Depends.

<p>Density functional theory calculations were applied to study four previously published metal-catalyzed [2,3]-rearrangements from onium ylide intermediates, in pursuit of generalizations about when, during these types of reactions, catalysts dissociate. Our results corroborate past studies where free ylide mechanisms were proposed to be operative. Calculations on case studies predict that the origin of metal-catalyst ‘falling off’ (dissociation) can be attributed primarily to the steric bulkiness of functional groups adjacent to the carbene carbon. </p>

Metal-Bound or Free Ylides as Reaction Intermediates in Metal-Catalyzed [2,3]-Sigmatropic Rearrangements? It Depends.

<p>Density functional theory calculations were applied to study four previously published metal-catalyzed [2,3]-rearrangements from onium ylide intermediates, in pursuit of generalizations about when, during these types of reactions, catalysts dissociate. Our results corroborate past studies where free ylide mechanisms were proposed to be operative. Calculations on case studies predict that the origin of metal-catalyst ‘falling off’ (dissociation) can be attributed primarily to the steric bulkiness of functional groups adjacent to the carbene carbon. </p>

Tertiary Enamides as Versatile and Valuable Substrates to Reach Chemical Diversity

Tertiary enamides display versatile reactivity and great stability compared to their enamine congeners. This review covers progress made in the development of new methods involving the enaminic reactivity of tertiary enamides with respect to the synthesis of complex nitrogen-containing compounds. A focus on the preparation of biologically active molecules is also presented. The syntheses reported herein are classified based on their reaction type. In addition, mechanistic insights are given for most of the new transformations.1 Introduction2 [2+2] Cycloadditions3 [4+2] Cycloadditions4 Electrocyclizations and Cycloisomerizations5 Sigmatropic Rearrangements6 Nucleophilic Additions7 Tertiary Enamides as Electrophiles8 Cross-Coupling Reactions9 Tertiary-Enamide-Assisted Reactions10 Conclusion and Perspectives