Preparation of Strained Axially Chiral (1,5)Naphthalenophanes by Photo-dehydro-Diels−Alder Reaction
| Autor: | Pablo Wessig, Annika Matthes |
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| Rok vydání: | 2011 |
| Předmět: |
Models
Molecular Circular dichroism Molecular Structure Stereochemistry Chemistry Circular Dichroism Absolute configuration Stereoisomerism General Chemistry Naphthalenes Crystallography X-Ray Biochemistry Catalysis Ring strain Chiral column chromatography Crystallography Colloid and Surface Chemistry Molecular geometry Luminescent Measurements Moiety Spectrophotometry Ultraviolet Enantiomer Diels–Alder reaction |
| Zdroj: | Journal of the American Chemical Society. 133:2642-2650 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/ja109118m |
| Popis: | The preparation of 10 (1,5)naphthalenophanes (10a-j) by photo-dehydro-Diels-Alder (PDDA) reaction is described. Owing to hindered rotation around the biaryl axis, compounds 10 are axially chiral and the separation of enantiomers by chiral HPLC was demonstrated in three cases (10a,b,e). The absolute configuration of the isolated enantiomers could be unambiguously determined by comparison of calculated and measured circular dichroism (CD) spectra. Furthermore, we analyzed ring strain phenomena of (1,5)naphthalenophanes 10. Depending on the length of the linker units, one can distinguish three classes of naphthalenophanes. Compounds 10a-c are highly strained (E(STR) = 7-31 kcal/mol), and the strain is caused by small bond angles in the linker unit and deformation of the naphthalene moiety. Another type of strain is observed if the linker unit becomes relatively long (10g,h) originating from transannular interactions and is comparable with the well-known strain of medium sized rings. The naphthalenophanes 10d-f with a linker length of 10-14 atoms are only marginally strained. To clearly discriminate the different sources of strain, we defined two geometrical parameters (average central dihedral angle δ(C) and naphthalene thickness D(N)) and demonstrated that they are well-suited to indicate naphthalene deformation of our naphthalenophanes 10 as well as of ten model naphthalenophanes (I-X) with different linker lengths and linking positions. |
| Databáze: | OpenAIRE |
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