Asymmetric Synthesis of Isochromanone Derivatives via Trapping Carboxylic Oxonium Ylides and Aldol Cascade

An efficient asymmetric synthesis of isochromanone derivatives was realized through Z-selective-1,3-OH insertion/aldol cyclization reaction involving acyclic carboxylic oxonium ylides. The combination of achiral dirhodium salts and chiral N,N’-dioxide-metal complexes, along...

One-pot Synthesis of Multi-substituted Conjugated Dienones by Trapping Allene Carbocation with Active Ylides

An Rh (II)/boron reagents co-catalyzed unprecedent transformation was established for a rapid construction of multi-substituted conjugated dienones under a mild condition by trapping allene carbocations with oxonium ylides from simple...

Catalyst-Controlled Regiodivergence in Rearrangements of Indole-Based Onium Ylides

We have developed catalyst-controlled regiodivergent rearrangements of onium-ylides derived from indole substrates. Oxonium ylides formed <i>in situ</i> from substituted indoles selectively undergo [2,3]- and [1,2]-rearrangements in the presence of a rhodium and copper catalyst, respectively. The combined experimental and density functional theory (DFT) computational studies indicate divergent mechanistic pathways involving a metal-free ylide in the rhodium catalyzed reaction favoring [2,3]-rearrangement, and a metal-coordinated ion-pair in the copper catalyzed [1,2]-rearrangement that recombines in the solvent-cage. The application<br>of our methodology was demonstrated in the first total synthesis of the indole alkaloid (±)-sorazolon B, which enabled the stereochemical reassignment of the natural product. Further functional group transformations of the rearrangement products to generate valuable synthetic intermediates were also demonstrated.

Catalyst-Controlled Regiodivergence in Rearrangements of Indole-Based Onium Ylides

We have developed catalyst-controlled regiodivergent rearrangements of onium-ylides derived from indole substrates. Oxonium ylides formed <i>in situ</i> from substituted indoles selectively undergo [2,3]- and [1,2]-rearrangements in the presence of a rhodium and copper catalyst, respectively. The combined experimental and density functional theory (DFT) computational studies indicate divergent mechanistic pathways involving a metal-free ylide in the rhodium catalyzed reaction favoring [2,3]-rearrangement, and a metal-coordinated ion-pair in the copper catalyzed [1,2]-rearrangement that recombines in the solvent-cage. The application<br>of our methodology was demonstrated in the first total synthesis of the indole alkaloid (±)-sorazolon B, which enabled the stereochemical reassignment of the natural product. Further functional group transformations of the rearrangement products to generate valuable synthetic intermediates were also demonstrated.

Diazocarbonyl Compounds in Organofluorine Chemistry

Diazocarbonyl compounds are useful substrates in di- and trifunctionalization reactions based on F/CF3/SCF3 introduction. In the presented reactions, various electrophilic F/CF3/SCF3-transfer reagents were used. The majority of the reactions were based on rhodium catalysis and the application of various oxygen nucleophiles, such as alcohols, cyclic/acyclic ethers, and carboxylic acids. The oxyfluorination reactions were further developed to provide a new fluorine-18 labeling method. Density functional theory (DFT) modeling studies were performed to get a deeper mechanistic understanding of these reactions. These DFT modeling studies indicated that the catalytic reactions proceed through formation of rhodium carbene and oxonium ylide intermediates. The oxonium ylides undergo tautomerization to enol ether type species that subsequently react with the electrophilic F/CF3/SCF3-transfer reagents. We also present an arylation–trifluoromethylthiolation reaction for simultaneous introduction of C–SCF3 and C–C bonds into diazocarbonyl compounds. This reaction does not proceed by rhodium catalysis, but follows a Hooz-type mechanism.1 Introduction2 Diazocarbonyl Compounds: Versatile Substrates in Organic ­Synthesis3 Fluorination, Trifluoromethylation, and Trifluoromethylthiolation of Diazo Substrates3.1 Metal-Free Reactions3.2 Metal-Catalyzed Reactions with Nucleophilic Reagents3.3 Metal-Catalyzed Reactions with Electrophilic Reagents4 Oxyfluorination Reactions4.1 Fluorobenziodoxole as a Fluorine Source4.2 [18F]Fluorobenziodoxole as a Fluorine Source for Radiolabeling4.3 Oxyfluorination with NFSI5 Oxytrifluoromethylation6 Oxytrifluoromethylthiolation7 Arylation–Trifluoromethylthiolation Reaction8 Conclusions and Outlook