Push-Pull Buta-1,2,3-trienes: Exceptionally Low Rotational Barriers of Cumulenic C=C Bonds and Proacetylenic Reactivity

Przemyslaw Gawel; Yi Lin Wu; Aaron D. Finke; Nils Trapp; Michal Zalibera; Corinne Boudon; Jean Paul Gisselbrecht; W. Bernd Schweizer; Georg Gescheidt; François Diederich

doi:10.1002/chem.201406583

Push-Pull Buta-1,2,3-trienes: Exceptionally Low Rotational Barriers of Cumulenic C=C Bonds and Proacetylenic Reactivity

Przemyslaw Gawel, Yi Lin Wu, Aaron D. Finke, Nils Trapp, Michal Zalibera, Corinne Boudon, Jean Paul Gisselbrecht, W. Bernd Schweizer, Georg Gescheidt^*, François Diederich

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

21 Scopus citations

Abstract

A variety of asymmetrically donor-acceptor-substituted [3]cumulenes (buta-1,2,3-trienes) were synthesized by developed procedures. The activation barriers to rotation ΔG^≠ were measured by variable temperature NMR spectroscopy and found to be as low as 11.8 kcal mol^-1, in the range of the barriers for rotation around sterically hindered single bonds. The central C=C bond of the push-pull-substituted [3]cumulene moiety is shortened down to 1.22 Å as measured by X-ray crystallography, leading to a substantial bond length alternation (BLA) of up to 0.17 Å. All the experimental results are supported by DFT calculations. Zwitterionic transition states (TS) of bond rotation confirm the postulated proacetylenic character of donor-acceptor [3]cumulenes. Additional support for the proacetylenic character of these chromophores is provided by their reaction with tetracyanoethene (TCNE) in a cycloaddition-retroelectrocyclization (CA-RE) cascade characteristic of donor-polarized acetylenes.

Original language	English (US)
Pages (from-to)	6215-6225
Number of pages	11
Journal	Chemistry - A European Journal
Volume	21
Issue number	16
DOIs	https://doi.org/10.1002/chem.201406583
State	Published - Apr 13 2015

Funding

Keywords

[3]cumulenes
bond length alternation
proacetylenic
push-pull chromophores
rotational barrier
zwitterions

ASJC Scopus subject areas

Catalysis
Organic Chemistry

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10.1002/chem.201406583

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title = "Push-Pull Buta-1,2,3-trienes: Exceptionally Low Rotational Barriers of Cumulenic C=C Bonds and Proacetylenic Reactivity",

abstract = "A variety of asymmetrically donor-acceptor-substituted [3]cumulenes (buta-1,2,3-trienes) were synthesized by developed procedures. The activation barriers to rotation ΔG≠ were measured by variable temperature NMR spectroscopy and found to be as low as 11.8 kcal mol-1, in the range of the barriers for rotation around sterically hindered single bonds. The central C=C bond of the push-pull-substituted [3]cumulene moiety is shortened down to 1.22 {\AA} as measured by X-ray crystallography, leading to a substantial bond length alternation (BLA) of up to 0.17 {\AA}. All the experimental results are supported by DFT calculations. Zwitterionic transition states (TS) of bond rotation confirm the postulated proacetylenic character of donor-acceptor [3]cumulenes. Additional support for the proacetylenic character of these chromophores is provided by their reaction with tetracyanoethene (TCNE) in a cycloaddition-retroelectrocyclization (CA-RE) cascade characteristic of donor-polarized acetylenes.",

keywords = "[3]cumulenes, bond length alternation, proacetylenic, push-pull chromophores, rotational barrier, zwitterions",

author = "Przemyslaw Gawel and Wu, {Yi Lin} and Finke, {Aaron D.} and Nils Trapp and Michal Zalibera and Corinne Boudon and Gisselbrecht, {Jean Paul} and Schweizer, {W. Bernd} and Georg Gescheidt and Fran{\c c}ois Diederich",

note = "Publisher Copyright: {\textcopyright} 2015 Wiley-VCH Verlag GmbH & Co. KGaA.",

year = "2015",

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doi = "10.1002/chem.201406583",

language = "English (US)",

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T2 - Exceptionally Low Rotational Barriers of Cumulenic C=C Bonds and Proacetylenic Reactivity

AU - Gawel, Przemyslaw

AU - Wu, Yi Lin

AU - Finke, Aaron D.

AU - Trapp, Nils

AU - Zalibera, Michal

AU - Boudon, Corinne

AU - Gisselbrecht, Jean Paul

AU - Schweizer, W. Bernd

AU - Gescheidt, Georg

AU - Diederich, François

PY - 2015/4/13

Y1 - 2015/4/13

N2 - A variety of asymmetrically donor-acceptor-substituted [3]cumulenes (buta-1,2,3-trienes) were synthesized by developed procedures. The activation barriers to rotation ΔG≠ were measured by variable temperature NMR spectroscopy and found to be as low as 11.8 kcal mol-1, in the range of the barriers for rotation around sterically hindered single bonds. The central C=C bond of the push-pull-substituted [3]cumulene moiety is shortened down to 1.22 Å as measured by X-ray crystallography, leading to a substantial bond length alternation (BLA) of up to 0.17 Å. All the experimental results are supported by DFT calculations. Zwitterionic transition states (TS) of bond rotation confirm the postulated proacetylenic character of donor-acceptor [3]cumulenes. Additional support for the proacetylenic character of these chromophores is provided by their reaction with tetracyanoethene (TCNE) in a cycloaddition-retroelectrocyclization (CA-RE) cascade characteristic of donor-polarized acetylenes.

AB - A variety of asymmetrically donor-acceptor-substituted [3]cumulenes (buta-1,2,3-trienes) were synthesized by developed procedures. The activation barriers to rotation ΔG≠ were measured by variable temperature NMR spectroscopy and found to be as low as 11.8 kcal mol-1, in the range of the barriers for rotation around sterically hindered single bonds. The central C=C bond of the push-pull-substituted [3]cumulene moiety is shortened down to 1.22 Å as measured by X-ray crystallography, leading to a substantial bond length alternation (BLA) of up to 0.17 Å. All the experimental results are supported by DFT calculations. Zwitterionic transition states (TS) of bond rotation confirm the postulated proacetylenic character of donor-acceptor [3]cumulenes. Additional support for the proacetylenic character of these chromophores is provided by their reaction with tetracyanoethene (TCNE) in a cycloaddition-retroelectrocyclization (CA-RE) cascade characteristic of donor-polarized acetylenes.

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KW - push-pull chromophores

KW - rotational barrier

KW - zwitterions

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Push-Pull Buta-1,2,3-trienes: Exceptionally Low Rotational Barriers of Cumulenic C=C Bonds and Proacetylenic Reactivity

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