| Reference Type | Journal (article/letter/editorial) |
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| Title | Conformation and geometry of cyclopropane rings having π-acceptor substituents: a theoretical and database study |
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| Journal | Acta Crystallographica Section B Structural Science |
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| Authors | Cruz-Cabeza, Aurora J. | Author |
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| Allen, Frank H. | Author |
| Year | 2011 (February 1) | Volume | 67 |
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| Issue | 1 |
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| Publisher | International Union of Crystallography (IUCr) |
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| DOI | doi:10.1107/s0108768110049517Search in ResearchGate |
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| Generate Citation Formats |
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| Mindat Ref. ID | 187458 | Long-form Identifier | mindat:1:5:187458:1 |
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| GUID | 0 |
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| Full Reference | Cruz-Cabeza, Aurora J., Allen, Frank H. (2011) Conformation and geometry of cyclopropane rings having π-acceptor substituents: a theoretical and database study. Acta Crystallographica Section B Structural Science, 67 (1) 94-102 doi:10.1107/s0108768110049517 |
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| Plain Text | Cruz-Cabeza, Aurora J., Allen, Frank H. (2011) Conformation and geometry of cyclopropane rings having π-acceptor substituents: a theoretical and database study. Acta Crystallographica Section B Structural Science, 67 (1) 94-102 doi:10.1107/s0108768110049517 |
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| In | (2011, February) Acta Crystallographica Section B Structural Science Vol. 67 (1) International Union of Crystallography (IUCr) |
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| Abstract/Notes | The 3e′ orbitals of cyclopropane have the correct symmetry to interact with low-lying unoccupied orbitals of π-acceptor substituents and maximum overlap occurs when the two orbital systems are parallel,i.e.when the π-acceptor bisects the ring in projection down the substituent bond. Since the cyclopropyl group is a common component of active pharmaceutical and agrochemical ingredients, it is important that these strong conjugative interactions are well modelled by computational techniques, and clearly represented in experimental crystal structures. Here we show that torsion angle distributions derived from crystal structure data in the Cambridge Structural Database are in excellent correspondence with torsional energy profiles computed using density functional theory (DFT) for a range of substituents: —COOR, —CONR2, —NO2, vinyl and phenyl. We also show that crystal structure information is invaluable in modelling conformations of compounds that contain multiply substituted rings, where steric interactions require some substituents to adopt energetically disfavoured conformations. Further, conjugative interactions with π-acceptors lead to significant asymmetry in the cyclopropane ring bond lengths and again the experimental and computational results are in excellent agreement. Such asymmetry effects are additive, and this explains bond-length variations in cyclopropane rings bearing two or more π-acceptor substituents. |
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