Sodium borohydride as a reagent for nucleophilic aromatic substitution by hydrogen: the role of hydride Meisenheimer adducts as reaction intermediates

Gold, Victor; Miri, Adhid Y.; Robinson, Stephen R.

doi:10.1039/p29800000243

Cited by 22 publications

(13 citation statements)

References 2 publications

(2 reference statements)

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“…Such Meisenheimer anions can be stabilized by strongly electron‐withdrawing substituents (e.g. NO 2 ), but generally eliminate a hydride to give an aromatic product . The dibenzyl calcium reagents (DMAT) 2 Ca⋅(THF) 2 and (4‐ t Bu‐benzyl) 2 Ca clearly underperformed (DMAT=2‐Me 2 N‐α‐Me 3 Si‐benzyl).…”

Section: Methodsmentioning

confidence: 99%

Alkene Transfer Hydrogenation with Alkaline‐Earth Metal Catalysts

et al. 2019

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The alkene transfer hydrogenation (TH) of a variety of alkenes has been achieved with simple AeN′′2 catalysts [Ae=Ca, Sr, Ba; N′′=N(SiMe3)2] using 1,4‐cyclohexadiene (1,4‐CHD) as a H source. Reaction of 1,4‐CHD with AeN′′2 gave benzene, N′′H, and the metal hydride species N′′AeH (or aggregates thereof), which is a catalyst for alkene hydrogenation. BaN′′2 is by far the most active catalyst. Hydrogenation of activated C=C bonds (e.g. styrene) proceeded at room temperature without polymer formation. Unactivated (isolated) C=C bonds (e.g. 1‐hexene) needed a higher temperature (120 °C) but proceeded without double‐bond isomerization. The ligands fully control the course of the catalytic reaction, which can be: 1) alkene TH, 2) 1,4‐CHD dehydrogenation, or 3) alkene polymerization. DFT calculations support formation of a metal hydride species by deprotonation of 1,4‐CHD followed by H transfer. Convenient access to larger quantities of BaN′′2, its high activity and selectivity, and the many advantages of TH make this a simple but attractive procedure for alkene hydrogenation.

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Section: Methodsmentioning

confidence: 99%

Alkene Transfer Hydrogenation with Alkaline‐Earth Metal Catalysts

et al. 2019

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“…All these data are in agreement with those reported in the literature. [45] Thus, according to NMR spectroscopic data we are adsorbing into the zeolite a solution of the sodium salt of pure Meisenheimer complex, and no other species, particularly 2,4-dinitroaniline, could be observed during adsorption.…”

Section: Resultsmentioning

confidence: 98%

“…Also the 13 C NMR spectrum agrees completely with the structure of the s complex formed by hydride attack at the 3-position of 2,4-dinitroaniline. [44][45][46] In addition to NMR spectroscopy, the Meisenheimer complex in acetonitrile solution exhibits a characteristic UV/Vis absorption band at 578 nm that can be used to identify unambiguously its presence in mixtures containing neutral 2,4-dinitroaniline (l max = 333 nm). All these data are in agreement with those reported in the literature.…”

Section: Resultsmentioning

confidence: 99%

Anionic Organic Guests Incorporated in Zeolites: Adsorption and Reactivity of a Meisenheimer Complex in Faujasites

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Concepción

Doménech

et al. 2005

Chemistry A European J

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Zeolites are suitable microporous hosts for positively charged organic species, but it is believed that they cannot adsorb organic anions. Pure Meisenheimer complex, derived from reduction of 2,4-dinitroaniline with NaBH4, was adsorbed inside faujasite cavities. Evidence for the internal incorporation of this negatively charged reaction intermediate comes from 1) XPS elemental analysis as a function of the depth of penetration into the particle, 2) the remarkable blue shift in lambda(max) of the Meisenheimer complex adsorbed on zeolite (ca. 470 nm) as compared to that in acetonitrile (580 nm) and 3) from the lack of reactivity with size-excluded hydride-acceptor reagents. Evidence is provided in support of an adsorption mechanism in which a neutral ion pair (alkali metal ion + Meisenheimer anion) is the actual species being adsorbed. In fact it appears that there is remarkable increase in the association constant for the ion-pair complex within the zeolite cavities as compared to DMF solution. Although this mechanism of adsorption as an ion-pair complex has precedents in the adsorption of some inorganic salts, what is novel is the notable increase in the stability and persistence of the Meisenheimer anion (a anionic reaction intermediate) as a result of zeolite inclusion. Adsorbed Meisenheimer complex exhibits much lower reactivity towards electron acceptors, oxygen, and water. Cyclic voltammetry of zeolite-modified electrodes reveals for the Meisenheimer complex adsorbed on LiY a reversible redox peak that is not observed in solution and has been interpreted as arising from site isolation and stabilisation of the electrochemically generated species.

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“…Because the amount of this metabolite from culture was insufficient for thorough spectroscopic analysis, it was necessary to synthesize the complex. From the literature, it was known that hydride complexes of polynitroaromatic compounds can be generated by hydride transfer by using NaBH 4 , Bu 3 SnH, (H 3 C) 4 NBH 4 , or (H 3 C) 4 NB 3 H 8 as donor (2,4,7,9,18,21). However, none of these studies included a strong acid, such as picric acid (with a pK a of 0.38, according to reference 3).…”

Section: Discussionmentioning

confidence: 99%

Hydride-Meisenheimer Complex Formation and Protonation as Key Reactions of 2,4,6-Trinitrophenol Biodegradation by Rhodococcus erythropolis

et al. 1999

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Biodegradation of 2,4,6-trinitrophenol (picric acid) byRhodococcus erythropolis HLPM-1 proceeds via initial hydrogenation of the aromatic ring system. Here we present evidence for the formation of a hydride-Meisenheimer complex (anionic ς-complex) of picric acid and its protonated form under physiological conditions. These complexes are key intermediates of denitration and productive microbial degradation of picric acid. For comparative spectroscopic identification of the hydride complex, it was necessary to synthesize this complex for the first time. Spectroscopic data revealed the initial addition of a hydride ion at position 3 of picric acid. This hydride complex readily picks up a proton at position 2, thus forming a reactive species for the elimination of nitrite. Cell extracts ofR. erythropolis HLPM-1 transform the chemically synthesized hydride complex into 2,4-dinitrophenol. Picric acid is used as the sole carbon, nitrogen, and energy source by R. erythropolisHLPM-1.

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Sodium borohydride as a reagent for nucleophilic aromatic substitution by hydrogen: the role of hydride Meisenheimer adducts as reaction intermediates

Cited by 22 publications

References 2 publications

Alkene Transfer Hydrogenation with Alkaline‐Earth Metal Catalysts

Alkene Transfer Hydrogenation with Alkaline‐Earth Metal Catalysts

Anionic Organic Guests Incorporated in Zeolites: Adsorption and Reactivity of a Meisenheimer Complex in Faujasites

Hydride-Meisenheimer Complex Formation and Protonation as Key Reactions of 2,4,6-Trinitrophenol Biodegradation by Rhodococcus erythropolis

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