Pd‐catalyzed Oxidative Cross‐coupling of Alkyl Chromium(0) Fischer Carbene Complexes with Organoboronic Acids

Abstract

Alkyl chromium(0) carbene complexes have been explored as the cross-coupling partners in the palladium-catalyzed reaction with aryl or alkenyl boronic acids. This coupling reaction displays the versatile reactivities of alkyl chromium(0) carbenes under palladium catalysis. Mechanistically, this transformation is proposed to involve deprotonation of the alkyl chromium carbene substrate to generate a vinyl chromium anion intermediate that undergoes transmetalation to organopalladium species and reductive elimination.

Sesquicarbene Complexes: Bonding at the Interface Between M–C Single Bonds and M═C Double Bonds

“…It is now beyond controversy that the double-bond character of gold carbene complexes is low. − For this reason, for possible further applications − and for their synthetic connection to late transition metal complexes by transmetalation of the carbenes, we chose chromium­(−I) in our study. It forms carbene complexes with stronger π-backbonds and thus broadens the perspective on the electronic structures of [M 2 C­(vinyl)] + species beyond what we have experimentally detected before. − …”

Electron‐Rich Oxycarbenes: New Synthetic and Catalytic Applications beyond Group 6 Fischer Carbene Complexes

“…[30] More recently, the same group reported a Pdcatalyzed oxidative cross-coupling of alkyl chromium(0) Fischer carbene complexes 4.1 with organoboronic acids 4.9 (Scheme 4B). [31]…”

Transition metal-catalyzed reactivity of carbenes with boronic acid derivatives for arylation (alkylation) and beyond

“…To find effective coupling partners, the Wang group, in 2018, reported the coupling of alkyl chromium(0) Fischer carbenes 136 with organoboronic acids 91 to yield ketones and α,β-unsaturated ketones 137 (Scheme 19). 35 Based on the observed product, two pathways were proposed. Initially, the formation of 138 took place through path A, which includes alkyl carbene transfer to palladium to form intermediate 143 (Scheme 19c), and then migratory insertion followed by β-hydride elimination and subsequent hydrolysis resulted in ketone 148 (Scheme 19c).…”