Selenide Ions as Catalysts for Homo- and Crossed-Tishchenko Reactions of Expanded Scope

Curran, Simon P.; Connon, Stephen J.

doi:10.1021/ol203439g

Cited by 57 publications

(28 citation statements)

References 50 publications

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“…7 Due to the propensity of nonchelating aldehydes to engage in decarbonylation, 8−10 Tishchenko dimerizations, 5 and aldol condensations, inter molecular hydroacylations are considerably more challenging. 11−13 Herein, we report the design and development of the first enantioselective intermolecular ketone hydroacylation.…”

Section: Introductionmentioning

confidence: 99%

Rh(I)-Catalyzed Intermolecular Hydroacylation: Enantioselective Cross-Coupling of Aldehydes and Ketoamides

Kou

Dong

2014

J. Am. Chem. Soc.

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Under Rh(I) catalysis, α-ketoamides undergo intermolecular hydroacylation with aliphatic aldehydes. A newly designed Josiphos ligand enables access to α-acyloxyamides with high atom-economy and enantioselectivity. On the basis of mechanistic and kinetic studies, we propose a pathway in which rhodium plays a dual role in activating the aldehyde for cross-coupling. A stereochemical model is provided to rationalize the sense of enantioinduction observed.

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Section: Introductionmentioning

confidence: 99%

Rh(I)-Catalyzed Intermolecular Hydroacylation: Enantioselective Cross-Coupling of Aldehydes and Ketoamides

Kou

Dong

2014

J. Am. Chem. Soc.

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“…[19] On the basis of these initial studies and literature reports, we propose the mechanism shown in Scheme 6. [20] Ketone 3 d binds to nickel to form complex 8 a, which can coordinate to an aldehyde (1) to give intermediate 8 b. Oxidative addition to the aldehyde CÀH bond generates 8 c, which reduces the hydrogen acceptor 3 d to yield acyl nickel alkoxide 8 d. [21] Ligand exchange with the nucleophile affords 8 e, and reductive elimination provides the final product. Coordination of ketone 3 d may occur prior to [22] or immediately after reductive elimination.…”

mentioning

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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“…This reaction exemplifies an atom-efficient synthesis of esters and it is industrially viable. A large number of compounds containing main group [28] [19a]. To the best of our knowledge, there have been no reports on bis(guanidinate) magnesium and calcium compounds use as catalysts for the Tishchenko reaction.…”

Section: Catalytic Activitymentioning

confidence: 99%

Bulky guanidinate stabilized homoleptic magnesium, calcium and zinc complexes and their catalytic activity in the Tishchenko reaction

Barman

Baishya

Nembenna

2015

Journal of Organometallic Chemistry

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Selenide Ions as Catalysts for Homo- and Crossed-Tishchenko Reactions of Expanded Scope

Cited by 57 publications

References 50 publications

Rh(I)-Catalyzed Intermolecular Hydroacylation: Enantioselective Cross-Coupling of Aldehydes and Ketoamides

Rh(I)-Catalyzed Intermolecular Hydroacylation: Enantioselective Cross-Coupling of Aldehydes and Ketoamides

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

Bulky guanidinate stabilized homoleptic magnesium, calcium and zinc complexes and their catalytic activity in the Tishchenko reaction

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