Photoexcited Pd(ii) auxiliaries enable light-induced control in C(sp³)–H bond functionalisation

Abstract

Visible light irradiation of 8-aminoquinoline Pd(ii) complexes initiates photoinduced electron transfer with alkyl halides, affording C–H halogenation over C–C bond adducts. A method for inert C(sp3)–H bond halogenation (Br, Cl and I) is reported.

Transition-Metal-Catalyzed, Coordination-Assisted Functionalization of Nonactivated C(sp3)–H Bonds

“…In 2020, the Polyzos group reported a creative method for the halogenation of β-C(sp 3 )−H bonds with alkyl halides (Scheme 133). 364 By visible light excitation of the palladacycle, an electron transfer to the alkyl halide produces a palladium(III) intermediate, which can either undergo disproportionation or be oxidized by Oxone to generate a palladium(IV) complex. Reductive elimination from the palladium(IV) complex affords the halogenation product in moderate to good yields.…”

Modeling Metal-Catalyzed Polyethylene Depolymerization: [(Phen)Pd(X)]+ (X = H and CH3) Catalyze the Decomposition of Hexane into a Mixture of Alkenes via a Complex Reaction Network

“…As part of a program at better understanding the mechanisms of metal-catalyzed C−H functionalization reactions, we have been using mass spectrometry-based methods to either interrogate solution-phase reaction mixtures 5,6 or probe fundamental gas-phase reactivity. 7,8 Recent work has demonstrated that group 10 cationic complexes [(phen)M(R)] + can catalyze deoxygenation reactions of fatty acids 9 and the acceptorless dehydrogenation of ethane (eq 1 and Scheme 1A; M = Ni, Pd, and Pt, R = H and CH 3 CH 2 ).…”

“…As part of a program at better understanding the mechanisms of metal-catalyzed C–H functionalization reactions, we have been using mass spectrometry-based methods to either interrogate solution-phase reaction mixtures , or probe fundamental gas-phase reactivity. , Recent work has demonstrated that group 10 cationic complexes [(phen)­M­(R)] + can catalyze deoxygenation reactions of fatty acids and the acceptorless dehydrogenation of ethane (eq and Scheme A; M = Ni, Pd, and Pt, R = H and CH 3 CH 2 ) . The fact that such complexes not only lead to cracking of the fatty acid backbone, as exemplified by the sequential reactions shown for the stearate complex (eqs and ), but can also activate the C–H bonds of ethane (eq ) suggested that they could be used as depolymerization catalysts. , …”

Mechanism of 8-Aminoquinoline-Directed Ni-Catalyzed C(sp3)–H Functionalization: Paramagnetic Ni(II) Species and the Deleterious Effect of Carbonate as a Base

“…Multinuclear NMR spectroscopy showed that other coordinating solvents such as MeCN or DMSO also gave adducts tentatively assigned as 7·NCMe and 7·DMSO , but these could not be isolated as crystalline solids. Diamagnetic Pd analogues are known. − As shown in Scheme a), the C–H activation of 3 liberates 1 equiv of [AQ piv ]H ( 1a ), which was observed by 1 H NMR spectroscopy. The C–H activation 5 in the absence of added base also produced 1a , presumably because the t BuCO 2 H produced by deprotonation of the C–H bond protonates unreacted 5 , generating [AQ piv ]H ( 1a ), which lowers the yield.…”