Activation of Chromium Catalysts by Photoexcited Hantzsch Ester for Decarboxylative Allylation of Aldehydes with Butadiene

Lin, Sheng; Chen, Yuqing; Yan, Huaipu; Liu, Yonghong; Sun, Yu‐Chen; Hao, Er‐Jun; Shi, Caizhe; Zhang, Dandan; Zhu, Nan; Shi, Lei

doi:10.1021/acs.orglett.1c03098

Cited by 25 publications

(20 citation statements)

References 37 publications

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“…Complementing this example, Shi and co-workers reported the decarboxylative allylation of aldehydes with butadiene through the photoexcitation of Hantzsch esters, obviating the need for exogenous photocatalysts. 48 Alongside our work, a number of related allylations of carbonyl compounds involving radicals enabled by dual catalysis have also been developed. 49−51 The Shi group devised an excellent three-component allylation of carbonyls with 1,3-butadiene by dual photoredox/Ti catalysis.…”

Section: Catalytic Generation Of Allylic Chromium Intermediatesmentioning

confidence: 99%

Merging Carbonyl Addition with Photocatalysis

Huang

Glorius

2022

Acc. Chem. Res.

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The carbonyl group stands as a fundamental scaffold and plays a ubiquitous role in synthetically important chemical reactions in both academic and industrial contexts. Venerable transformations, including the aldol reaction, Grignard reaction, Wittig reaction, and Nozaki− Hiyama−Kishi reaction, constitute a vast and empowering synthetic arsenal. Notwithstanding, twoelectron mechanisms inherently confine the breadth of accessible reactivity and topological patterns. Fostered by the rapid development of photoredox catalysis, combing well-entrenched carbonyl addition and radicals can harness several unique and increasingly sustainable transformations. In particular, unusual carbon−carbon and carbon−heteroatom disconnections, which are out of reach of two-electron carbonyl chemistry, can be conceived. To meet this end, a novel strategy toward the utilization of simple carbonyl compounds as intermolecular radical acceptors was developed. The reaction is enabled by visible-light photoredox-initiated hole catalysis. In situ Brønsted acid activation of the carbonyl moiety prevents β-scission from occurring. Furthermore, this regioselective alkyl radical addition reaction obviates the use of metals, ligands, or additives, thus offering a high degree of atom economy under mild conditions. On the basis of the same concept and the work of Schindler and co-workers, carbonyl−olefin cross-metathesis, induced by visible light, has also been achieved, leveraging a radical Prins-elimination sequence. Recently, dual chromium and photoredox catalysis has been developed by us and Kanai, offering a complementary approach to the revered Nozaki−Hiyama−Kishi reaction. Leveraging the intertwined synergy between light and metal, several radical-to-polar crossover transformations toward eminent molecular motifs have been developed. Reactions such as the redox-neutral allylation of aldehydes and radical carbonyl alkylation can harvest the power of light and enable the use of catalytic chromium metal. Overall, exquisite levels of diastereoselectivity can be enforced via highly compact transition states. Other examples, such as the dialkylation of 1,3-dienes and radical carbonyl propargylation portray the versatile combination of radicals and carbonyl addition in multicomponent coupling endeavors. Highly valuable motifs, which commonly occur in complex drug and natural product architectures, can now be accessed in a single operational step. Going beyond carbonyl addition, seminal contributions from Fagnoni and MacMillan preconized photocatalytic HAT-based acyl radical formation as a key aldehyde valorization strategy. Our group articulated this concept, leveraging carboxy radicals as hydrogen atom abstractors in high regio-and chemoselective carbonyl alkynylation and aldehyde trifluoromethylthiolation. This Account, in addition to the narrative of our group and others' contributions at the interface between carbonyl addition and radical-based photochemistry, aims to provide core guiding foundations toward novel disruptive synthetic development...

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Section: Catalytic Generation Of Allylic Chromium Intermediatesmentioning

confidence: 99%

Merging Carbonyl Addition with Photocatalysis

Huang

Glorius

2022

Acc. Chem. Res.

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“…Recently, Hao and Shi reported a similar catalytic threecomponent coupling of aldehydes 1, 1,3-diene 24, and NHPI ester 32 (Scheme 10). 44 They utilized Hantzsch ester (HE) as a photoactive reductant for the chromium catalyst. 45 Considering the reduction potential of the excited state of HE [E 1/2 (HE •+ /HE*) = -2.28 V vs SCE], 45 chromium(III) species was reduced by HE* [E 1/2 (Cr(III)/Cr(II)) = -0.41 V vs SCE].…”

Section: Short Review Synthesismentioning

confidence: 99%

Recent Progress in Chromium-Mediated Carbonyl Addition Reactions

Katayama¹,

Mitsunuma²,

Kanai³

2021

Synthesis

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Organochromium(III) species are versatile nucleophiles in complex molecule synthesis due to their high functional group tolerance and chemoselectivity for aldehydes. Traditionally, carbonyl addition reactions of organochromium(III) species were performed through reduction of organohalides either using stoichiometric chromium(II) salts or catalytic chromium salts in the presence of stoichiometric reductants (such as manganese(0)). Recently, alternative methods emerged involving organoradical formation from readily available starting materials (e.g. N-hydroxyphthalimide esters, alkenes, and alkanes), followed by trapping the radical with stoichiometric or catalytic chromium(II) salts. Such methods, especially using catalytic chromium(II) salts, will lead to the development of sustainable chemical processes minimizing salt wastes and number of synthetic steps. In this review, we describe methods for generation of organochromium(III) species for addition reactions to carbonyl compounds, classified by nucleophiles.

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“…29,30 Inspired by these achievements, we hope to harness the reduction potential of HE* for chromium catalysis. 31 Herein, we report the first photochemical NHK coupling of alkenyl triflates and aldehydes enabled by photoexcited HE* (Figure 1c).…”

mentioning

confidence: 92%

“…Very recently, utilization of photoexcited HE* as a potential photoreductant (−2.28 V versus SCE) for metallaphotoredox catalysis appealed to great interests. Melchiorre and Molander respectively reported that photoexcited HE* and its analogs can reduce Ni to low valence catalytically active species for C–C bond coupling. , Inspired by these achievements, we hope to harness the reduction potential of HE* for chromium catalysis . Herein, we report the first photochemical NHK coupling of alkenyl triflates and aldehydes enabled by photoexcited HE* (Figure c).…”

mentioning

confidence: 93%

Photochemical Nozaki–Hiyama–Kishi Coupling Enabled by Excited Hantzsch Ester

et al. 2022

Self Cite

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This work reports the first photochemical Nozaki−Hiyama−Kishi coupling enabled by bioinspired Hantzsch ester. The salient feature of this process is that commercially available and low-cost organic photoactive Hantzsch ester can serve as both an electron and a proton donor to reduce Cr/Ni to lowvalent species and hydrolyze the Cr III -alkoxy bond, thus bypassing the use of stoichiometric metallic reductants and additives such as TMSCl and Cp 2 ZrCl 2 . The mild conditions and operationally easy method showed broad compatibility with various alkenyl triflates and aldehydes, including electron-poor pentafluorobenzaldehyde which failed under previous conditions.

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Activation of Chromium Catalysts by Photoexcited Hantzsch Ester for Decarboxylative Allylation of Aldehydes with Butadiene

Cited by 25 publications

References 37 publications

Merging Carbonyl Addition with Photocatalysis

Merging Carbonyl Addition with Photocatalysis

Recent Progress in Chromium-Mediated Carbonyl Addition Reactions

Photochemical Nozaki–Hiyama–Kishi Coupling Enabled by Excited Hantzsch Ester

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