Der 2×3‐Werkzeugkasten der metallorganischen Methoden zur regiochemisch erschöpfenden Funktionalisierung

Schlosser, Manfred

doi:10.1002/ange.200300645

Cited by 104 publications

(9 citation statements)

References 98 publications

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“…In the case of transition-metal-mediated directed oxidations, the conformational effects resulting from the intermediate metallacycles have a critical impact on chemoselectivity. [5] While the oxidation of benzene derivatives has a rich history dating back to early studies on electrophilic aromatic substitution and the Heck reaction, [72] research centered on metalmediated catalytic methods is a vibrant area of investigation.…”

Section: Activation Of Sp 2 Centersmentioning

confidence: 99%

If CH Bonds Could Talk: Selective CH Bond Oxidation

2011

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C–H oxidation has a long history and an ongoing presence in research at the forefront of chemistry and interrelated fields. As such, numerous highly useful texts and reviews have been written on this subject. Logically, these are generally written from the perspective of the scope and limitations of the reagents employed. This minireview instead attempts to emphasize chemoselectivity imposed by the nature of the substrate. Consequently many landmark discoveries in the field of C–H oxidation are not discussed, but hopefully the perspective taken herein will allow for the more ready incorporation of C–H oxidation reactions into synthetic planning.

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Section: Activation Of Sp 2 Centersmentioning

confidence: 99%

If CH Bonds Could Talk: Selective CH Bond Oxidation

2011

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“…We thus aim to provide a method which allows one to predict the selectivity of halogen-magnesium exchange reactions of polyfunctional compounds. [7] Attempts to determine the kinetics of these reactions to reveal details of the reaction mechanisms have so far not been conclusive. Received: September 5, 2007Published online: November 23, 2007 .…”

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confidence: 99%

Relative Rates of Bromine–Magnesium Exchange Reactions in Substituted Bromobenzene Derivatives

et al. 2007

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Dedicated to Professor Klaus Hafner on the occasion of his 80th birthdayThe accessibility of functionalized Grignard reagents has opened new dimensions in organic synthesis.[1] One of us has previously demonstrated that treatment of substituted bromoarenes with iPrMgCl·LiCl provides a straightforward access to functionalized aryl Grignard reagents by brominemagnesium exchange.[2] In accord with the suggested mechanism for these reactions, [3] electron-acceptor groups have been observed to facilitate this conversion. We have now determined the relative rates of such exchange reactions to facilitate a targeted use of these reactions on polyfunctional compounds.The influence of substituents on the rates of brominemagnesium exchange has been determined by competition experiments. For this purpose, mixtures of two differently substituted bromobenzene derivatives have been combined with less than one equivalent of iPrMgCl·LiCl in THF. The ratio of the resulting aryl magnesium chlorides was then derived by gas chromatographic determination of the product ratio obtained after quenching with iodineThe relative reactivities of R1 and R2 towards iPrMgCl· LiCl can be calculated by Equation (1) Alternative ways to calculate k, for example, by substituting the absolute concentrations [R1] 0 , [R1] t , [R2] 0 , and [R2] t into Equation (1), usually gave less reproducible results, and are presented in the Supporting Information for comparison. In several cases, control experiments were performed to demonstrate that the mode of quenching did not affect the results (Table 1 and Supporting Information). The independence of the product ratios on the reaction time is evidence that the product ratio is under kinetic control, that is, no exchange reactions take place between bromoarenes and aryl magnesium chlorides (Scheme 2, Table 1, and Supporting Information). Furthermore, the exchange depicted in Scheme 2 has been excluded by treating 3-cyanophenylmagScheme 1. Determination of relative bromine-magnesium exchange rates. X, Y = H, F, Cl, Br, CF 3 , CO 2 tBu, CN. [a]

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“…Let us consider an arene bearing two different heteroelements at 1- and 2-positions or 1- and 3-positions. Is it really possible to introduce further substituents optionally at any of the vacant positions by merely relying on a handful of advanced organometallic methods, as asserted recently? The only way to make this claim credible is to subject it to scrutiny by a variety of “tough” model cases. To this end, we have examined as substrates 3-fluorophenol, several difluorophenols and trifluorophenols, , 4-, 5-, 6-, and 7-fluoroindole, 4-bromo-6- and -7-fluoro-2-(trifluoromethyl)quinoline, N -methyl- and N -phenyl-5-(trifluoromethyl)pyrazole, various bromo-, chloro-, and iodo(trifluoromethyl)pyridines, 3-fluoropyridine, and 2,4-difluoropyridine …”

Section: Introductionmentioning

confidence: 99%

Selective Functionalization of 2-Fluoropyridine, 2,3-Difluoropyridine, and 2,5-Difluoropyridine at Each Vacant Position

Bobbio

Schlosser

2005

J. Org. Chem.

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The concept of "regioexhaustive substitution" has been successfully applied to 2-fluoro-, 2,3-difluoro-, and 2,5-difluoropyridine. All vacant positions were amenable to regioselective metalation and subsequent carboxylation by employing either chlorine as a neighboring site activating protective group or trimethylsilyl as a neighboring site screening protective group. In this way, approximately half a dozen fluorinated pyridinecarboxylic acids were derived from each starting material.

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Der 2×3‐Werkzeugkasten der metallorganischen Methoden zur regiochemisch erschöpfenden Funktionalisierung

Cited by 104 publications

References 98 publications

If CH Bonds Could Talk: Selective CH Bond Oxidation

If CH Bonds Could Talk: Selective CH Bond Oxidation

Relative Rates of Bromine–Magnesium Exchange Reactions in Substituted Bromobenzene Derivatives

Selective Functionalization of 2-Fluoropyridine, 2,3-Difluoropyridine, and 2,5-Difluoropyridine at Each Vacant Position

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