Which Hydrogen Atom Is First Transferred in the NAD(P)H Model Hantzsch Ester Mediated Reactions via One-Step and Multistep Hydride Transfer?

Zhu, Xiao‐Qing; Liu, You‐Cheng; Cheng, Jiang

doi:10.1021/jo9905571

Cited by 70 publications

(37 citation statements)

References 16 publications

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“…From computational studies, the N-alkoxylphthalimide 1 first undergoes single electron reduction to generate the radical anion CP1 . After protonation by the Hantzsch ester radical cation, the alkyl radical intermediate CP2 was formed with 5.8 kcal/mol endothermically (black line) (Azizi et al., 2015, McSkimming and Colbran, 2013, Zheng and You, 2012, Turovska et al., 2008, Zhu et al., 1999). The N-O bond was then homolytically cleaved to form the alkoxyl radical CP3 via the transition state TS1 with an activation energy of 18.8 kcal/mol.…”

Section: Resultsmentioning

confidence: 99%

Visible-Light-Induced Alkoxyl Radicals Enable α-C(sp3)-H Bond Allylation

et al. 2020

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SummaryThe alkoxyl radical is an essential reactive intermediate in mechanistic studies and organic synthesis with hydrogen atom transfer (HAT) reactivity. However, compared with intramolecular 1,5-HAT or intermolecular HAT of alkoxyl radicals, the intramolecular 1,2-HAT reactivity has been limited to theoretical studies and rarely synthetically utilized. Here we report the first selective 1,2-HAT of alkoxyl radicals for α-C(sp3)-H bond allylation of α-carbonyl, α-cyano, α-trifluoromethyl, and benzylic N-alkoxylphthalimides. The mechanistic probing experiments, electron paramagnetic resonance (EPR) studies, and density functional theory (DFT) calculations confirmed the 1,2-HAT reactivity of alkoxyl radicals, and the use of protic solvents lowered the activation energy by up to 10.4 kcal/mol to facilitate the α-C(sp3)-H allylation reaction.

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Section: Resultsmentioning

confidence: 99%

Visible-Light-Induced Alkoxyl Radicals Enable α-C(sp3)-H Bond Allylation

et al. 2020

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“…The introduced bivalent cations face strong interactions with the nitrogen in DHPE, which has a lone pair of electrons . These electrons are very effective and are responsible for the reduction of Pd 2+ ions and, finally, the reducing agent is automatically converted into its aromatic form as shown in the reaction mechanism in Figure S6 in the Supporting Information . As the ‘nonaromatic–aromatic’ transformation is very facile, we could judiciously slow the electron‐transfer process, which slows down the reduction process and generates morphologically important Pd nanostructures through the introduction of bivalent cation based bromide salts.…”

Section: Resultsmentioning

confidence: 99%

Metal Bromide Controlled Interfacial Aromatization Reaction for Shape‐Selective Synthesis of Palladium Nanostructures with Efficient Catalytic Performances

Dutta

Ray

Roy

et al. 2016

Chemistry A European J

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Herein, the effect of diverse metal bromides for the shape evolution of palladium nanostructures (Pd NS) has been demonstrated. Aromaticity-driven reduction of bromopalladate(II) is optimized to reproducibly obtain different Pd NS at the water/organic layer interface. In this soft interfacial strategy, a redox potential driven reaction has been performed, forming the thermodynamically more stable (>10(4) -fold) PdBr4 (2-) precursor from PdCl4 (2-) by adding extra metal bromides. In the process, the reductant, Hantzsch dihydropyridine ester (DHPE), is aromatized. Interestingly, alkali metal bromides devoid of coordination propensity exclusively evolve Pd nanowires (Pd NWs), whereas in the case of transition metal bromides the metal ions engage the 'N' donor of DHPE at the interface, making the redox reaction sluggish. Hence, controlled Pd nanoparticles growth is observed, which evolves Pd broccolis (Pd NBRs) and Pd nanorods (Pd NRs) at the interface in the presence of NiBr2 and CuBr2 , respectively, in the aqueous solution. Thus, the effect of diverse metal bromides in the reaction mixture for tailor-made growth of the various Pd NS is reported. Among the as-synthesized materials, the Pd NWs stand to be superior catalysts and their efficiency is almost 6 and 2.5 times higher than commercial 20 % Pd/C in the electrooxidation of ethanol and Cr(VI) reduction reaction by formic acid, respectively.

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“…Kinetic isotope effects in the range of 1.2 to 1.3 for mono‐deuterated Hantzsch ester at position 1 (ND) and 5.3 to 6.0 for an at position 4 di‐deuterated Hantzsch ester D 2 ‐2 were observed. Consequently it was assumed that the CH bond dissociation at position 4 of the Hantzsch ester is the rate‐limiting step, in terms of a direct hydride transfer 15…”

Section: Resultsmentioning

confidence: 99%

On‐Column Reaction Set‐Up for High‐Throughput Screenings and Mechanistic Investigations

et al. 2015

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As creeningp latform, which offers ah ighthroughput approach as well as an easy investigation of kinetic isotope effects,a pplicable to aw ide range of reactions is presented. To illustrate the high potential of this approach, the asymmetric transfer hydrogenation of methyl benzoylformate with copper(II) bis(oxazoline) and Hantzsch ester was examined. Accordingly,t he enantioselectivitieso ft he reaction performed on-column in am icrocapillary were comparable to standard reaction conditions, however, we were able achieve catalysis and analysis in as ingle step in less than 30 min. Thet hroughput can be increasedb ys imultaneous investigation of different substratesw ithout increasing the overall analysis time.U se of di-deuterated Hantzsch ester allowed us to investigate the kinetic isotope effect of the transfer hydrogenation reactiono nly requiring am inute amount of the deuterated transfer hydrogenation reagent. Hence we were able to get further insights into the mechanism of the asymmetric transfer hydrogenation using Hantzsch ester as hydrogen source.T he here presented technique is broadly applicable to studyi sotope effects on av ery small scale,w hich is ar apid and an inexpensivea lternative comparedtoc onventional experiments.Keywords: asymmetric transfer hydrogenation;c opper(II) bis(oxazoline);H antzsch ester;h igh-throughput;k inetic isotope effect;o n-column reaction gas chromatography

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Which Hydrogen Atom Is First Transferred in the NAD(P)H Model Hantzsch Ester Mediated Reactions via One-Step and Multistep Hydride Transfer?

Cited by 70 publications

References 16 publications

Visible-Light-Induced Alkoxyl Radicals Enable α-C(sp3)-H Bond Allylation

Visible-Light-Induced Alkoxyl Radicals Enable α-C(sp3)-H Bond Allylation

Metal Bromide Controlled Interfacial Aromatization Reaction for Shape‐Selective Synthesis of Palladium Nanostructures with Efficient Catalytic Performances

On‐Column Reaction Set‐Up for High‐Throughput Screenings and Mechanistic Investigations

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