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

Hoshimoto, Yoichi; Hayashi, Yasumasa; Suzuki, Haruka; Ohashi, Masato; Ogoshi, Sensuke

doi:10.1002/ange.201206186

Cited by 18 publications

(5 citation statements)

References 53 publications

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“…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.…”

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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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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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“…Furthermore, acid sensitive carbamate group (4f) or aldehydes and formamides (4g-h), known substrates in Ni(0)-catalyzed C-H functionalizations were tolerated. [42][43][44] Once again, all products were obtained with stereoselectivities higher than 20:1 in favor of E isomers.…”

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confidence: 83%

Nickel-Catalyzed Double Bond Transposition under Kinetic Control

Carvalho-Junior

Oliveira

2022

Preprint

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Taming the reactivity of nickel catalysts is a never-ending inspiration to discover new complexes, ligands, and reaction protocols. Here, we report that a simple combination of Ni(COD)2 and Lewis acids allows activation of allylic CH bonds. Their synergism eases oxidative addition and 1,3-hydrogen atom relocation to yield unprecedented double bond monotransposition. Unique features of this work include polar inner-sphere mechanism, kinetically favored double bond transposition, ligand-controlled stereoselective E or Z isomer distribution, mechanistic insights by control experiments and NMR monitoring.

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

Cited by 18 publications

References 53 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

Nickel-Catalyzed Double Bond Transposition under Kinetic Control

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