Attempts directed towards the synthesis of intermediate (aryne)chromium complexes from aryl triflates and from (haloarene)chromium complexes

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Original languageEnglish
Pages (from-to)3132-3141
Number of pages10
JournalEuropean Journal of Organic Chemistry
Issue number16
Publication statusPublished - 20 Apr 2012

Abstract

The generation of (η6-aryne)chromium complexes as reactive intermediates was investigated in two ways. Although earlier attempts directed towards triflate eliminations from a variety of tricarbonyl(phenyl triflate)chromium complexes had failed, more electron-rich phenyl triflate complexes were considered. This was accomplished either by substitution with two methoxy groups in the arene ligand or by replacement of one of the three carbonyl ligands of the tricarbonylchromium complex with triphenylphosphane. However, the attempted elimination still did not take place; in spite of the increased electron densities in the aromatic ligands, anionic thia-Fries rearrangements were observed in high yields at -78 °C. As an alternative, elimination of lithium fluoride was tested. Tricarbonyl(2-lithiofluorobenzene) chromium(0) was generated by tin/lithium exchange. After hydrolytic workup, tricarbonyl(fluorobenzene)chromium was obtained as the main product, indicating that the lithiation step had been successful. A dimeric side product provided evidence for the intermediacy of (benzyne)tricarbonylchromium.

Keywords

    Anionic thia-Fries rearrangement, Arynes, Chromium, Haloarenes, Lithiation, Phenyl triflate, Rearrangement

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Attempts directed towards the synthesis of intermediate (aryne)chromium complexes from aryl triflates and from (haloarene)chromium complexes. / Werner, Georg; Butenschön, Holger.
In: European Journal of Organic Chemistry, No. 16, 20.04.2012, p. 3132-3141.

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abstract = "The generation of ({\^I}·6-aryne)chromium complexes as reactive intermediates was investigated in two ways. Although earlier attempts directed towards triflate eliminations from a variety of tricarbonyl(phenyl triflate)chromium complexes had failed, more electron-rich phenyl triflate complexes were considered. This was accomplished either by substitution with two methoxy groups in the arene ligand or by replacement of one of the three carbonyl ligands of the tricarbonylchromium complex with triphenylphosphane. However, the attempted elimination still did not take place; in spite of the increased electron densities in the aromatic ligands, anionic thia-Fries rearrangements were observed in high yields at -78 °C. As an alternative, elimination of lithium fluoride was tested. Tricarbonyl(2-lithiofluorobenzene) chromium(0) was generated by tin/lithium exchange. After hydrolytic workup, tricarbonyl(fluorobenzene)chromium was obtained as the main product, indicating that the lithiation step had been successful. A dimeric side product provided evidence for the intermediacy of (benzyne)tricarbonylchromium.",
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T1 - Attempts directed towards the synthesis of intermediate (aryne)chromium complexes from aryl triflates and from (haloarene)chromium complexes

AU - Werner, Georg

AU - Butenschön, Holger

PY - 2012/4/20

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KW - Anionic thia-Fries rearrangement

KW - Arynes

KW - Chromium

KW - Haloarenes

KW - Lithiation

KW - Phenyl triflate

KW - Rearrangement

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