Nickel Catalysis Enables Hetero [2+2+1] Cycloaddition between Yne‐Isothiocyanates and Isonitriles with Low Catalyst Loading

Liu, Ruijuan; Wang, Pengfei; Yuan, Wen‐Kui; Wen, Li‐Rong; Li, Ming

doi:10.1002/adsc.201601271

“…Gu and co-workers reported as imilar transformation, employing t-BuOOH as an alternative oxidant (Scheme 12). [36] Their conditions tolerate functionalized acrylamides 51 in addition to benzamides (45), although also only in combination with tertiary aliphatic and xylyl isocyanides.T he chemoselectivity is sufficiently high to simultaneously tolerate the presence of other directing groups on substrate 51 (e.g., (di)azine,p yrazole), selectively affording quite ar ange of functionalized iminophthalimides 52 in moderate to excellent yields.T he authors proposed similar intermediates for this reaction towards 52 as were postulated for the imidoylative CÀHf unctionalization reaction of benzamides 45 described in Scheme 10.…”

Section: Methodsmentioning

confidence: 99%

“…[35] Interestingly,under these conditions,another iminoindolinone isomer 49 was predominantly obtained. The key step in this reaction is most likely the oxidative alkoxyimidoylation of 45 to eventually form imidate 50.T his involves an initial directing group assisted C À Hactivation via CMD and a1 ,1-migratory insertion of the precoordinated isocyanide to afford intermediate 48 [36] Their conditions tolerate functionalized acrylamides 51 in addition to benzamides (45), although also only in combination with tertiary aliphatic and xylyl isocyanides.T he chemoselectivity is sufficiently high to simultaneously tolerate the presence of other directing groups on substrate 51 (e.g., (di)azine,p yrazole), selectively affording quite ar ange of functionalized iminophthalimides 52 in moderate to excellent yields.T he authors proposed similar intermediates for this reaction towards 52 as were postulated for the imidoylative CÀHf unctionalization reaction of benzamides 45 described in Scheme 10.…”

Section: Angewandte Chemiementioning

confidence: 99%

“…Thec yclonickelate intermediate 70 is formed by oxidative cycloaddition. [45] Control experiments indicated that the active catalyst is indeed aNi 0 species,w hich is generated in situ from the Ni II precursor without addition of an external reducing agent. Notably,t he catalyst loading is low,but the reaction still tolerates arather broad range of aliphatic,a romatic,a nd a-acidic isocyanides.…”

Section: Imidoylations Initiated By Cyclometalationmentioning

confidence: 99%

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Base Metal Catalyzed Isocyanide Insertions

Collet

¹

,

Roose

²

,

Ruijter

³

et al. 2019

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Isocyanides are diverse C1 building blocks considering their potential to react with nucleophiles, electrophiles, and radicals. Therefore, perhaps not surprisingly, isocyanides are highly valuable as inputs for multicomponent reactions (MCRs) and other one‐pot cascade processes. In the field of organometallic chemistry, isocyanides typically serve as ligands for transition metals. The coordination of isocyanides to metal centers alters the electronic distribution of the isocyano moiety, and reaction pathways can therefore be accessed that are not possible in the absence of the metal. The tunable reactivity of the isocyanide functional group by transition metals has evolved into numerous useful applications. Especially palladium‐catalyzed isocyanide insertion processes have emerged as powerful reactions in the past decade. However, reports on the use of earth‐abundant and cheap base metals in these types of transformations are scarce and have received far less attention. In this Minireview, we focus on these emerging base metal catalyzed reactions and highlight their potential in synthetic organic chemistry. Although mechanistic studies are still scarce, we discuss distinct proposed catalytic cycles and categorize the literature according to 1) the (hetero)atom bound to and 2) the type of bonding with the transition metal in which the (formal) insertion occurs.

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“…A hetero‐[2+2+1] Pauson–Khand‐type cycloaddition of 2‐alkynylaryl isothiocyanates 68 and isocyanides yields thieno[2,3‐ b ]indoles 69 (Scheme ). The cyclonickelate intermediate 70 is formed by oxidative cycloaddition . Control experiments indicated that the active catalyst is indeed a Ni 0 species, which is generated in situ from the Ni II precursor without addition of an external reducing agent.…”

Section: Insertions Of Isocyanides Into Carbon–metal Speciesmentioning

confidence: 99%

Base Metal Catalyzed Isocyanide Insertions

Collet

¹

,

Roose

²

,

Ruijter

³

et al. 2019

View full text Add to dashboard Cite

Isocyanides are diverse C1 building blocks considering their potential to react with nucleophiles, electrophiles, and radicals. Therefore, perhaps not surprisingly, isocyanides are highly valuable as inputs for multicomponent reactions (MCRs) and other one‐pot cascade processes. In the field of organometallic chemistry, isocyanides typically serve as ligands for transition metals. The coordination of isocyanides to metal centers alters the electronic distribution of the isocyano moiety, and reaction pathways can therefore be accessed that are not possible in the absence of the metal. The tunable reactivity of the isocyanide functional group by transition metals has evolved into numerous useful applications. Especially palladium‐catalyzed isocyanide insertion processes have emerged as powerful reactions in the past decade. However, reports on the use of earth‐abundant and cheap base metals in these types of transformations are scarce and have received far less attention. In this Minireview, we focus on these emerging base metal catalyzed reactions and highlight their potential in synthetic organic chemistry. Although mechanistic studies are still scarce, we discuss distinct proposed catalytic cycles and categorize the literature according to 1) the (hetero)atom bound to and 2) the type of bonding with the transition metal in which the (formal) insertion occurs.

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“…Recently, transition-metal-catalyzed cascade bicyclization of o-alkynylphenyl isothiocyanates with various nucleophiles provides a new and powerful synthetic strategy to construct different heterocycles such as indoles, [8] quinoline, [9] thiazine [10] and so on. For example, Saito group [8c] developed an Rh-mediated Pauson-Khand (PK) reaction to construct a 3-substituted-2H-thieno [2,3-b]indol-2-ones by using o-alkynylphenyl isothiocyanates and CO as the substrates (Scheme 1, a).…”

Section: Introductionmentioning

confidence: 99%