Dual Catalysis in Rhodium (II) Carbenoid Chemistry

Rh(II)/Pd(0) Dual Catalysis: Interception of Ammonium Ylide with Allyl Palladium to Construct 2,2-Disubstituted Tetrahydroquinoline Derivatives

New synthetic methods to construct 2,2-disubstituted tetrahydroquinoline derivatives are of significant value in pharmaceutical chemistry. Herein, a Rh(II)/Pd(0) dual-catalyzed diazo α-aminoallylation reaction has been developed between allylpalladium(II) and ammonium ylides derived from the Rh₂(OAc)₄-mediated intramolecular N-H bond insertion reaction of diazo compounds, affording various 2,2-disubstituted tetrahydroquinoline derivatives in good yields up to 93% with high chemoselectivities under mild reaction conditions. A substrate scope investigation reveals broad ester substituent tolerance, and control experiments provide the basis for a proposed reaction mechanism.

CuX Dual Catalysis: Construction of Oxazolo[2,3-b][1,3]oxazines via a Tandem CuAAC/Ring Cleavage/[4+2+3] Annulation Reaction

CuX as a simple dual catalyst strategy that promotes the tandem transformations of fused oxazolo[2,3-b][1,3]oxazines has been developed. Copper catalyzed terminal ynones, sulfonyl azides, and nitriles for the CuAAC/ring cleavage/[4+2] annulation reaction, while the halogen catalyzed ring cleavage and [2+3] annulation of oxiranes to form the final fused products. This study provides a four-component, one-pot strategy for synthesizing complex fused heterocycles from simple ingredients and expands the application of CuAAC in organic synthesis.