Rhodium(III)-Catalyzed Redox-Neutral Cascade [3 + 2] Annulation of N-Phenoxyacetamides with Propiolates via C–H Functionalization/Isomerization/Lactonization

Abstract

A Rh(III)-catalyzed cascade [3 + 2] annulation of Nphenoxyacetamides with propiolates under mild conditions using the internal oxidative O−N bond as the directing group has been achieved. This catalytic system provides a regio-and stereoselective access to benzofuran-2(3H)-ones bearing exocyclic enamino motifs with exclusive Z configuration selectivity, acceptable to good yields and good functional group compatibility. Mechanistic investigations by experimental and density functional theory studies suggest that a consecutive process of C−H functionalization/isomerization/lactonization is likely to be involved in the reaction.

Transition Metal Promoted Cascade Heterocycle Synthesis through C−H Functionalization

“…In 2018 Xia, Zhang and co‐workers reported the N ‐aryloxyacetamides directed cascade synthesis of benzofuran‐3‐( 2H )‐ones by using rhodium as the catalyst and propiolates as coupling partners . More recently, in 2019, Zhu and co‐workers applied a similar strategy for the C−H functionalization/cyclization to synthesize a series of benzofuran‐2( 3H )‐ones 90 .…”

Tandem Reactions of Ynones: via Conjugate Addition of Nitrogen‐, Carbon‐, Oxygen‐, Boron‐, Silicon‐, Phosphorus‐, and Sulfur‐Containing Nucleophiles

“…Finally, cyclization and dehydration could afford the desired product. In 2018, the Zhang group described the O−N bond cleavage of N ‐phenoxyacetamide under similar conditions [Eq. (15‐2)] (Scheme ).…”

Rh(III)-Catalyzed C–H Bond Activation for the Construction of Heterocycles with sp3-Carbon Centers

“…In the same year, Zhang's group also employed N-aryloxyacetamides as a starting substrate and coupled with propiolates to furnish the synthesis of benzofuran-2(3H)-ones with good yields via a Rh(III)-catalyzed cascade [3 + 2] annulation, in which NHAc group was used as an internal oxidizing directing group. The result enaminoate motif can be easily converted into heterocycle with sp 3 carbon center by a simple oxidative manipulation (Scheme 5) [48]. Its mechanistic investigations by experimental and density functional theory (DFT) studies suggest that a consecutive process of C−H bond functionalization/isomerization/lactonization is likely to be involved in this transformation.…”