Radical-type Reactions Controlled by Cobalt: From Carbene Radical Reactivity to the Catalytic Intermediacy of Reactive o-Quinodimethanes

Grotenhuis, Colet te; Bruin, Bas de

doi:10.1055/s-0037-1610204

Cited by 22 publications

(9 citation statements)

References 12 publications

(16 reference statements)

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“…Since our group is focusing on C–H activation using metallocarbenes and metallonitrenes for the catalytic formation of new C–C and C–N bonds, 56−62 we considered that a related acyl nitrene transfer strategy could be useful for the synthesis of N -acyl amidines. However, realizing new strategies to convert acyl nitrenes in a selective manner is rather troublesome.…”

Section: Introductionmentioning

confidence: 99%

Efficient Copper-Catalyzed Multicomponent Synthesis of N-Acyl Amidines via Acyl Nitrenes

Vliet

Polak

Siegler³

et al. 2019

J. Am. Chem. Soc.

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Direct synthetic routes to amidines are desired, as they are widely present in many biologically active compounds and organometallic complexes. N-Acyl amidines in particular can be used as a starting material for the synthesis of heterocycles and have several other applications. Here, we describe a fast and practical copper-catalyzed three-component reaction of aryl acetylenes, amines, and easily accessible 1,4,2-dioxazol-5-ones to N-acyl amidines, generating CO2 as the only byproduct. Transformation of the dioxazolones on the Cu catalyst generates acyl nitrenes that rapidly insert into the copper acetylide Cu–C bond rather than undergoing an undesired Curtius rearrangement. For nonaromatic dioxazolones, [Cu(OAc)(Xantphos)] is a superior catalyst for this transformation, leading to full substrate conversion within 10 min. For the direct synthesis of N-benzoyl amidine derivatives from aromatic dioxazolones, [Cu(OAc)(Xantphos)] proved to be inactive, but moderate to good yields were obtained when using simple copper(I) iodide (CuI) as the catalyst. Mechanistic studies revealed the aerobic instability of one of the intermediates at low catalyst loadings, but the reaction could still be performed in air for most substrates when using catalyst loadings of 5 mol %. The herein reported procedure not only provides a new, practical, and direct route to N-acyl amidines but also represents a new type of C–N bond formation.

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Section: Introductionmentioning

confidence: 99%

Efficient Copper-Catalyzed Multicomponent Synthesis of N-Acyl Amidines via Acyl Nitrenes

Vliet

Polak

Siegler³

et al. 2019

J. Am. Chem. Soc.

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“…Cobalt(II) complexes of porphyrins are unique potent metalloradical catalysts that are found to be useful for a wide variety of cyclization and insertion reactions . The research groups of Zhang, de Bruin, and Chattopadhyay have significantly contributed to Co II metalloradical chemistry for the synthesis of a myriad of carbo- and heterocycles. − The metalloradical catalysis is a promising approach, which has attractive features over traditional Fischer-type carbene chemistry; however, certain aspects of metalloradical catalysis have seldom been explored and need more attention such as (1) the rate of carbene radical generation between two distinct carbene precursors and (2) the reactivity of the carbene radicals in multicomponent reactions.…”

Section: Resultsmentioning

confidence: 99%

Stereoselective gem-Difunctionalization of Diazo Compounds with Vinyl Sulfoxonium Ylides and Thiols via Metalloradical Catalysis

Bhardwaj,

Gopalakrishnan,

Deshwal

et al. 2024

ACS Catal.

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Multicomponent reactions that involve carbenes with nucleophiles and electrophiles have demonstrated broad applications in synthetic chemistry. However, because of the high reactivity of transient carbenes, reactions involving two carbene precursors with the nucleophile in the presence of a metal catalyst remain unexplored. Herein, a three-component stereoselective gem-difunctionalization of diazo compounds with thiols and vinyl sulfoxonium ylide is disclosed via Co(II)-based metalloradical catalysis. The key aspect of the present strategy is to exploit the intrinsic difference in the reactivity of vinyl sulfoxonium ylides and diazo compounds with thiol and metal catalysts. The present Doyle−Kirmse rearrangement of a sulfonium ylide involves a convergent assembly of two in situ-generated intermediates, such as allyl sulfide and αmetalloalkyl radical complex, to provide expeditious access to tertiary sulfide scaffolds. Combined experimental and quantum chemical calculations unveil the intricate mechanism of this three-component reaction. Furthermore, theoretical studies on noncovalent interactions of selectivity-determining transition states explain the origin of the experimentally obtained diastereoselectivity.

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“…Transition metal carbene chemistry has matured over the past few decades into an established field within both inorganic chemistry and homogeneous catalysis. 1 Their applications range from unique electronic, magnetic, and photophysical properties to a wide variety of synthetic methods, such as several C–H and X–H insertion reactions, 2 ring-forming and expansion transformations, 3 alkene metathesis, 4 and C1 polymerization 5 inter alia .…”

Section: Introductionmentioning

confidence: 99%

Carbene Radicals in Transition-Metal-Catalyzed Reactions

et al. 2023

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Discovered as organometallic curiosities in the 1970s, carbene radicals have become a staple in modern-day homogeneous catalysis. Carbene radicals exhibit nucleophilic radical-type reactivity orthogonal to classical electrophilic diamagnetic Fischer carbenes. Their successful catalytic application has led to the synthesis of a myriad of carbo- and heterocycles, ranging from simple cyclopropanes to more challenging eight-membered rings. The field has matured to employ densely functionalized chiral porphyrin-based platforms that exhibit high enantio-, regio-, and stereoselectivity. Thus far the focus has largely been on cobalt-based systems, but interest has been growing for the past few years to expand the application of carbene radicals to other transition metals. This Perspective covers the advances made since 2011 and gives an overview on the coordination chemistry, reactivity, and catalytic application of carbene radical species using transition metal complexes and catalysts.

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Radical-type Reactions Controlled by Cobalt: From Carbene Radical Reactivity to the Catalytic Intermediacy of Reactive o-Quinodimethanes

Cited by 22 publications

References 12 publications

Efficient Copper-Catalyzed Multicomponent Synthesis of N-Acyl Amidines via Acyl Nitrenes

Efficient Copper-Catalyzed Multicomponent Synthesis of N-Acyl Amidines via Acyl Nitrenes

Stereoselective gem-Difunctionalization of Diazo Compounds with Vinyl Sulfoxonium Ylides and Thiols via Metalloradical Catalysis

Carbene Radicals in Transition-Metal-Catalyzed Reactions

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