Wittig rearrangements of aralkyl alkyl ethers

Garst, John F.; Smith, Carl

doi:10.1021/ja00422a041

Cited by 75 publications

(33 citation statements)

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“…4d When alcohol 3a was subjected to our arylation conditions, no arylation product was observed (Scheme 1B) and starting material was recovered. In contrast, ether 4ad underwent [1,2]-Wittig rearrangement upon exposure to LiN(SiMe 3 ) 2 in the absence of the Pd(NIXANTPHOS)-based catalyst in 80% yield (Scheme 1C).…”

Section: Resultsmentioning

confidence: 99%

“…3 α-Alkoxy carbanions are known to undergo [1,2]-Wittig rearrangements to generate alcohols 3 . 4 If anion 2 could be intercepted by a palladium catalyst via rapid transmetallation, 5 arylation may outcompete the [1,2]-Wittig rearrangement of 2 to generate the desired aryl(pyridine-2-yl)methyl ether core, 4 . Compound 4 , possessing, a more acidic benzylic hydrogen than 2 , may undergo deprotonation under the basic reaction conditions followed by [1,2]-Wittig rearrangement to form tertiary alcohols 5 .…”

Section: Introductionmentioning

confidence: 99%

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Chemoselective palladium-catalyzed deprotonative arylation/[1,2]-Wittig rearrangement of pyridylmethyl ethers

2016

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Chemoselective palladium-catalyzed deprotonative arylation/[1,2]-Wittig rearrangement of pyridylmethyl ethers

2016

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“…In close related systems it has been estimated that the non-geminate recombination is about 1/16 as fast as geminate recombination. 19 As a consequence, if most of the radical pairs escape geminate recombination and diffuse in the solvent, it is very unlike that free nitroarene radical anion can scavenge all alkyl radicals, particularly when the independent decay processes of the latter radical species occur at a very fast rate. Conversely, when geminate recombination is a very efficient process, there is an higher probability that the little amount of nitroarene radical anions which had diffused in the solvent can scavenge a large part of alkyl radicals.…”

Section: Resultsmentioning

confidence: 99%

Polar Versus Electron Transfer Pathway in the Reaction of Alkyl Lithium and Alkyl Grignard Reagents with Mononttroarenes: Factors Affecting Product Distribution

Bartoli

Bosco

Dalpozzo

et al. 1989

Paramagnetic Organometallic Species in Activation/Selectivity, Catalysis

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The reaction of nitroarenes with alkyl lithium and alkyl Grignard reagents can mainly give 1,4 and 1,6-addition products, nitroarene radical anion and alkyl radical decay products. Employing magnesium instead of lithium derivatives and low temperatures, the yields in conjugate addition products increase to the detriment of the amount of nitroarene radical anion; while steric hindrances favour the redox process. These findings can be interpreted on the basis of a single electron transfer (SET) pathway in which conjugate addition derivatives and nitroarene radical anion can be considered as typical in-cage and out-of-cage products respectively. However, there are no conclusive evidences to exclude that the so-called cage products can arise from a polar pathway. Nevertheless, this question can be settled if the existence of a continuos mechanistic spectrum from 'full polar' to 'full SET' pathways is accepted on the basis of the Pross's electron shift theory.

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“…In the other case, the reaction can proceed via a tightly bound transition state, which may also lead to substitution products. 3,4,[7][8][9][10][11][12][13][14][15] Early mechanistic studies were carried out by Garst on the reactions of benzophenone ketyls with alkyl bromides, 16,17 where it was shown that, along with an ET mechanism that leads to radical formation, one also obtains alkylation products. More recent mechanistic studies were carried out by Screttas and Michascrettas, 18 who used 13 C spin transfer NMR techniques to try to quantify the inner sphere tightly bound transition states.…”

Section: Introductionmentioning

confidence: 99%

A Single Transition State Serves Two Mechanisms. The Branching Ratio for CH₂O^•- + CH₃Cl on Improved Potential Energy Surfaces

Shaik

Schlegel

2006

J. Phys. Chem. A

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The reaction of formaldehyde radical anion with methyl chloride, CH 2 O •-+ CH 3 Cl, is an example in which a single transition state leads to two products: substitution at carbon (Sub(C), CH 3 CH 2 O • + Cl -) and electron transfer (ET, CH 2 O + CH 3• + Cl -). The branching ratio for this reaction has been studied by ab initio molecular dynamics (AIMD). The energies of transition states and intermediates were computed at a variety of levels of theory and compared to accurate energetics calculated by the G3 and CBS-QB3 methods. A bond additivity correction has been constructed to improve the Hartree-Fock potential energy surface (BAC-UHF). A satisfactory balance between good energetics and affordable AIMD calculations can be achieved with BH&HLYP/6-31G(d) and BAC-UHF/6-31G(d) calculations. Approximately 200 ab initio classical trajectories were calculated for each level of theory with initial conditions sampled from a thermal distribution at 298 K at the transition state. Three types of trajectories were distinguished: trajectories that go directly to ET product, trajectories that go to Sub(C) product, and trajectories that initially go into the Sub(C) valley and then dissociate to ET products. The BH&HLYP/6-31G(d) calculations overestimate the number of nonreactive and direct ET trajectories because the transition state is too early. For the BH&HLYP and BAC-UHF methods, about one-third of the trajectories that initially go into the Sub(C) valley dissociate to ET products, compared to just over half with UHF/6-31G(d) in the earlier study. This difference can be attributed to a better value for the calculated energy release from the initial transition state and to an improved Sub(C) f ET barrier height with the BH&HLYP and BAC-UHF methods.

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Wittig rearrangements of aralkyl alkyl ethers

Cited by 75 publications

References 10 publications

Chemoselective palladium-catalyzed deprotonative arylation/[1,2]-Wittig rearrangement of pyridylmethyl ethers

Chemoselective palladium-catalyzed deprotonative arylation/[1,2]-Wittig rearrangement of pyridylmethyl ethers

Polar Versus Electron Transfer Pathway in the Reaction of Alkyl Lithium and Alkyl Grignard Reagents with Mononttroarenes: Factors Affecting Product Distribution

A Single Transition State Serves Two Mechanisms. The Branching Ratio for CH₂O^•- + CH₃Cl on Improved Potential Energy Surfaces

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Wittig rearrangements of aralkyl alkyl ethers

Cited by 75 publications

References 10 publications

Chemoselective palladium-catalyzed deprotonative arylation/[1,2]-Wittig rearrangement of pyridylmethyl ethers

Chemoselective palladium-catalyzed deprotonative arylation/[1,2]-Wittig rearrangement of pyridylmethyl ethers

Polar Versus Electron Transfer Pathway in the Reaction of Alkyl Lithium and Alkyl Grignard Reagents with Mononttroarenes: Factors Affecting Product Distribution

A Single Transition State Serves Two Mechanisms. The Branching Ratio for CH2O•- + CH3Cl on Improved Potential Energy Surfaces

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A Single Transition State Serves Two Mechanisms. The Branching Ratio for CH₂O^•- + CH₃Cl on Improved Potential Energy Surfaces