Photo‐Catalyzed Redox‐Neutral 1,2‐Dialkylation of Alkenes

Abstract

Difunctionalization of alkenes enables construction of complex compounds in one pot. In this report, we presented an intermolecular, redoxneutral three-component dicarbofunctionalization of activated alkenes under mild reaction conditions. The mechanistic studies indicated tertiary alkyl radicals from oxalate salts were first added to alkenes in Giese-type fashion, followed by nucleophilic addition with aldehydes to produce the desired 1,2-dialkylation products. The catalyst system does not require any additives, with good functional group compatibility, regioselectivity, and constructs two tertiary carbon centers simultaneously.

Asymmetric synthesis of unnatural α-amino acids through photoredox-mediated C–O bond activation of aliphatic alcohols

“…Therefore, the primary factor precluding the use of secondary and primary alcohol substrates in the disclosed transformation is the unfavorable oxidative SET. As has been proposed previously, 24 the secondary factor for the decreased reactivity of primary and secondary alcohol substrates is likely the reduced rate constant for decarboxylation of the respective oxyacyl radicals 10 (k dec z 10 5 s −1 and 10 2 s −1 for the oxalates derived from tertiary and secondary/primary alcohols, respectively). 46 Finally, the uorescence quenching experiments with PC4 and N-sulnyl imine 4 displayed no quenching (Fig.…”

Visible-Light-Induced Photoredox 1,2-Dialkylation of Styrenes with α-Carbonyl Alkyl Bromides and Pyridin-1-ium Salts

“…Consequently, the possible mechanism for this alkene dialkylation protocol was proposed (Scheme ). − The alkyl radical intermediate A is formed directly by single-electron transfer between α-carbonyl alkyl bromide 2a and the [Ru­(bpy) 3 ] 2+ * intermediate, which is irradiated of the [Ru­(bpy) 3 ] 2+ species by blue LED light. , Addition of the alkyl radical intermediate A across the CC bond of alkene 1 affords the new alkyl radical intermediate B , followed by addition to pyridin-1-ium salt 3 to form the alkylated pyridin-1-ium radical cation intermediate C . , Finally, single electron oxidation and dealkylation of intermediate C afford the desired product 4 .…”

“…The alkene difunctionalization reaction has been emerged as a powerful and straightforward synthetic methodology that simultaneously introduces two functional groups into the alkene scaffolds for significantly increasing molecular complexity in organic chemistry. − In this content, dialkylation of alkenes presents particularly appealing for prolonging carbon chains through incorporation of two alkyl groups across a C–C double bond. − While transition-metal-catalyzed dialkylation reactions of alkenes with two alkyl electrophiles or a combination of alkyl electrophiles and alkyl organometallics, respectively, merging the classical cross-couplings have been well investigated in the past few decades [Scheme A­(a,b)], − radical-mediated variants remain scarce and turn out to be challenging due to the competing reactivity of the alkyl radicals from the alkyl electrophiles and the resulting alkyl radicals from radical addition across the alkenes [Scheme A­(c)]. , In 2019, our group developed the first three-component dialkylation of alkenes with common alkanes and nucleophilic 1,3-dicarbonyl compounds via synergistic photoredox catalysis and iron oxidative catalysis for producing two functionalized 1,3-dicarbonyl compounds . The reaction is initiated by the sp 3 carbon-centered radical intermediate via abstraction of a hydrogen from an alkane with DTBP and is terminated by single electron oxidation of the resulting alkyl radicals to generate the alkyl cations, followed by reaction with nucleophiles.…”

Cu-catalyzed alkylarylation of alkenes via N-directed remote C(sp3)–H functionalization

“…14 To our knowledge, few examples of three-component dicarbofunctionalization of alkenes using N -centered radicals have been reported. Based on our previous research 15 and continued interest in the nitrogen-radical triggered 1,5-HAT strategy, we herein report a copper-catalyzed alkylarylation of alkenes via N -centered radical initiated remote C–H activation (Scheme 1d), which might offer a new way for synthesizing diverse complex molecules containing 1,1-diaryl motifs.…”