Iron-catalyzed deconstructive alkylation through chlorine radical induced C–C single bond cleavage under visible light

Abstract

Selective C-C single bond cleavage of simple compounds is a highly challenging and desired process. Herein, a chlorine radical-induced deconstructive C-C bond alkylation with alcohols and alkenes catalyzed by iron...

Deconstructive Cyanomethylation Enabled by Radical Cross‐Coupling through Multiple C−C Bond and C−H Bond Cleavage

“…Thus, as a reasonable result, when stoichiometric base (collidine) was applied, the elimination procedure was sharply locked and the ring‐opening product 3 a’’’ was observed (entries 5–7 ). The formation of 3 a’’’ was strong evidence for the formation of chlorine radicals from FeCl 3 under irradiation, consistent with our former studies [11b,d] . Furthermore, these experiments illustrated a reversible process between 1 a and 6 e in the presence of the photo‐induced Fe(III)Cl n system, which was involved in pathway 2 .…”

“…When an ether substrate 1 a‐Me was subjected to the standard conditions, the ring‐opening product could not be obtained, indicating that the RO−H bond was crucial for the formation of the alkoxyl radical (Scheme 5g). According to our and other's [20] prior studies of chlorine radical, we proposed that a quick formation of an adduct of Cl⋅ with the oxygen atom of the alcohol happened after irradiation of the iron chloride complex, then an alkoxy radical was formed with the assistance of collidine [11b,d] . A base was essential for the procedure due to a stronger BDE of O−H than H−Cl [21] .…”

“…With the scope of tertiary cyclohexanols, we envisaged that other kinds of tertiary alcohols could also act as precursors of carbon radicals in selective radical cross‐coupling processes with the loss of an acetone [11b,d,14] . As shown in Scheme 3, a range of tertiary alcohols proved to be viable coupling partners upon β ‐C−C bond fragmentation, providing the corresponding alkylated product successfully, including readily available α‐arylketo ( 5 a – 5 f ) and α‐aryl substituted ( 5 g – 5 p ) tertiary alcohols.…”

Iron‐Catalyzed Oxidative C−C Bond Cleavage of Unstrained Tertiary Alkyl Aromatics to Arylketones

“…The hydroxyl radical generated from a Fenton process [11] would abstract a hydrogen atom of tertiary alkyl aromatic to provide the tertiary benzyl radical II , followed by trapping with a hydroperoxide radical [11] to produce the tertiary benzyl hydroperoxide III that would give rise to the tertiary benzyloxy radical IV [7–8] by iron‐mediated homolysis. Thereafter, C α –C β bond fragmentation of the tertiary benzyloxy radical IV [1b,3a,r–t] affords the corresponding aryl ketone V with a methyl radical.…”

Divergent Construction of Azaheterocycles via Alkoxyl Radical-Triggered C–C Bond Cleavage/Cyclization of N-Functionalized Acrylamides

“…10 Thanks to the diverse generation of alkoxy radicals, a variety of C−C and C−heteroatom bonds could be constructed successfully under different catalytic systems. Among them, radical-mediated additions are one of the commonly used bond-forming patterns (Scheme 1c); therein, various unsaturated compounds such as electron-deficient heteroaromatics 11 and alkenes 12 were investigated. In this regard, our group disclosed several cheap metal-catalyzed three-component difunctionalization reactions of styrenes initiated by alkoxy-radical-triggered radical C−C bond cleavage.…”