Nickeladihydrofuran. Key intermediate for nickel-catalyzed reaction of alkyne and aldehyde

Ogoshi, Sensuke; Arai, T.; Kurosawa, Hideo

doi:10.1039/b717261c

Cited by 94 publications

(79 citation statements)

References 38 publications

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“…[25] This coordination also inhibits the formation of the Tishchenko side product by disrupting the formation of a cycloisomerization intermediate between two aldehydes. [26] We have described a novel nickel-catalyzed dehydrogenative cross-coupling of aldehydes. Our method generates hindered esters and provides a needed complement to NHCcatalyzed oxidative esterification.…”

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confidence: 99%

Nickel‐Catalyzed Dehydrogenative Cross‐Coupling: Direct Transformation of Aldehydes into Esters and Amides

Whittaker

Dong

2014

Angewandte Chemie

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By exploring a new mode of nickel-catalyzed crosscoupling, a method to directly transform both aromatic and aliphatic aldehydes into either esters or amides has been developed. The success of this oxidative coupling depends on the appropriate choice of catalyst and organic oxidant, including the use of either a,a,a-trifluoroacetophenone or excess aldehyde. Mechanistic data that supports a catalytic cycle involving oxidative addition into the aldehyde C À H bond is also presented.Developing nickel catalysts for the selective oxidation of CÀH bonds is an emerging strategy that overcomes the need for precious metals and enables new transformations.[1] Our laboratory has previously focused on the oxidation of aldehydes under Rh, Ru, and Co catalysis.[2] Inspired by the promise of base metals, we considered that Ni-catalyzed cross-couplings of aldehydes could be classified into three general types: redox-neutral, reductive, and oxidative ( Figure 1). For example, Ogoshis cross-coupling between two aldehydes is a redox-neutral method that generates ester bonds.[3] In comparison, reductive coupling reactions generate carbon-carbon bonds in the presence of an external reductant (e.g., Et 2 Zn).[4] A complementary Ni-catalyzed cross-coupling in the presence of an external oxidant, however, represents an undeveloped mode of reactivity that warrants study.[5] Herein, we showcase a unified approach for transforming aldehyde CÀH bonds into both CÀO and CÀN bonds using Ni-catalyzed dehydrogenative cross-couplings. [6] The transformation of aldehydes into esters and amides in one step is an attractive goal that has been pursued using precious-metal catalysts, [7] base-metal catalysts with strong oxidants, [8] and N-heterocyclic carbene (NHC) catalysis.[9]Whereas these methods are promising, a method that couples aromatic and aliphatic aldehydes with alcohols, anilines, and amines has yet to be achieved. Towards addressing this challenge, we chose to examine carbonyl compounds as mild oxidants by hydrogen transfer.[10]Our initial studies focused on cross-coupling benzaldehyde (1 a) and 2-propanol (2 a) in the presence of various hydrogen acceptors. We discovered that NHC ligands in 1,4-dioxane produced the most promising results (Scheme 1). [11] In the absence of any Ni salts, we observed no reactivity. However, in the presence of [Ni(cod) 2 ] with benzaldehyde as both the substrate and hydrogen acceptor, we observed the formation of the desired ester 4 a and Tishchenko homodimer 5 a in a 5.9:1 ratio. To suppress the Tishchenko pathway, we sought an acceptor that undergoes reduction faster than benzaldehyde (1 a). Whereas the addition of acetone (3 a) and cyclobutanone (3 b) decreased the rate of the desired crosscoupling, both benzophenone (3 c) and a,a,a-trifluoroacetophenone (3 d) showed a remarkable enhancement in rate and selectivity for 4 a. As a result, we were able to use equimolar quantities of the coupling partners and 1

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confidence: 99%

Nickel‐Catalyzed Dehydrogenative Cross‐Coupling: Direct Transformation of Aldehydes into Esters and Amides

Whittaker

Dong

2014

Angewandte Chemie

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“…[25] This coordination also inhibits the Tishchenko byproduct by disrupting the formation of a cycloisomerization intermediate between two aldehydes. [26] …”

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confidence: 99%

Nickel‐Catalyzed Dehydrogenative Cross‐Coupling: Direct Transformation of Aldehydes into Esters and Amides

2014

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By exploring a new mode of Ni-catalyzed cross-coupling, we have developed a protocol to transform both aromatic and aliphatic aldehydes into either esters or amides directly. The success of this oxidative coupling depends on the appropriate choice of catalyst and organic oxidant, including the use of either α,α,α-trifluoroacetophenone or excess aldehyde. We present mechanistic data that supports a catalytic cycle involving oxidative addition into the aldehyde C–H bond.

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“…They concluded that the former was more plausible because of the formation of decarbonylated olefinic products in the reaction with benzaldehyde. On the other hand, during the course of our research on heteronickelacycles, [7] we demonstrated that an oxanickelacycle prepared by oxidative cyclization of an alkyne and an aldehyde with Ni 0 slowly decomposed to furnish an a,b-enone and no decarbonylated product. [7b] This result indicated that the oxanickelacycle can act as a potential intermediate in Ni 0 -catalyzed alkyne hydroacylation (Scheme 1, path b).…”

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Synthesis of Five‐ and Six‐Membered Benzocyclic Ketones through Intramolecular Alkene Hydroacylation Catalyzed by Nickel(0)/N‐Heterocyclic Carbenes

et al. 2012

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Transition-metal-catalyzed hydroacylation has been accepted as a promising synthetic method to form carbon-carbon bonds between an aldehyde and unsaturated compounds, such as alkenes, alkynes, and ketones. A number of catalyst systems have been developed, and high enatio-, regio-, and chemo-selectivity has been achieved.[1] Despite these extensive efforts and praiseworthy results, an inevitable side reaction persists: decarbonylation from an acyl metal intermediate, which causes a decrease in atom-efficiency and a deactivation of the catalyst through the coordination of carbon monoxide (Scheme

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Nickeladihydrofuran. Key intermediate for nickel-catalyzed reaction of alkyne and aldehyde

Cited by 94 publications

References 38 publications

Nickel‐Catalyzed Dehydrogenative Cross‐Coupling: Direct Transformation of Aldehydes into Esters and Amides

Nickel‐Catalyzed Dehydrogenative Cross‐Coupling: Direct Transformation of Aldehydes into Esters and Amides

Nickel‐Catalyzed Dehydrogenative Cross‐Coupling: Direct Transformation of Aldehydes into Esters and Amides

Synthesis of Five‐ and Six‐Membered Benzocyclic Ketones through Intramolecular Alkene Hydroacylation Catalyzed by Nickel(0)/N‐Heterocyclic Carbenes

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