InBr₃‐Catalyzed Coupling Reaction between Electron‐Deficient Alkenyl Ethers with Silyl Enolates for Stereoselective Synthesis of 1,5‐Dioxo‐alk‐2‐enes

Abstract

A coupling reaction of electron‐deficient alkenyl ethers with silyl enolates catalyzed by InBr3 was achieved. Various silyl enolates and 2‐carbonylalkenyl ethers were applicable, giving the corresponding 1,5‐dioxo‐alk‐2‐enes with perfect stereoselectivity of the alkene moieties. The present coupling reaction proceeds via the 1,4‐addition of silyl enolates to alkenyl ethers followed by elimination of silyl alkoxides, in which moderate‐Lewis acidic InBr3 performs both the activation of alkenyl ethers and the elimination of alkoxy groups regardless of the presence of various coordinative functional groups.

Mechanistic Insight into Rh-Catalyzed C(sp2)–O Bond Cleavage Applied to Cross-Coupling Reaction of Benzofurans with Aryl Grignard Reagents

“…Although the pioneering work by Wenkert et al in 1979 on the Ni-catalyzed Kumada–Tamao–Corriu-type cross-coupling of alkenyl and aryl ethers with Grignard reagents exemplified the C–O bond cleavage of simple ethers, the yields were not always satisfactory . In the last 15 years, cross-coupling reaction of ethereal compounds with organometallic reagents via C­(sp 2 )–O bond cleavage has been developed using Ni, − Cr, Fe, Ru, and Rh as the catalysts, although the use of directing groups for C–O bonds cleavage was necessary in some cases. ,, …”