Combined experimental and theoretical studies of regio- and stereoselectivity in reactions of β-isoxazolyl- and β-imidazolyl enamines with nitrile oxides

Ilya V. Efimov,
Marsel Z. Shafikov,
Nikolai A. Beliaev,
Natalia N. Volkova,
Tetyana V. Beryozkina,
Wim Dehaen,
Zhijin Fan,
Viktoria V. Grishko,
Gert Lubec,
Pavel A. Slepukhin and
Vasiliy A. Bakulev

Full Research Paper
Published 15 Nov 2016

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1. Graphical Abstract
2. Figure 1: Biologically active isoxazoles conjugated to other azole rings.
  
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3. Scheme 1: Reactions of azolyl enamines with nitrile oxides.
  
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4. Figure 2: Structures of starting enamines 1 and hydroxamoyl chlorides 2.
  
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5. Scheme 2: Synthesis of 4-azolylisoxazoles 4a–p from enamines 1a–e and hydroxamoyl chlorides 2a–h. Reaction co...
  
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6. Figure 3: Imidazolylisoxazole 4a according to XRD data in the thermal ellipsoids of the 50% probability level....
  
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7. Figure 4: Isoxazolylisoxazole 4p according to XRD data with thermal ellipsoids of 50% probability level.
  
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8. Scheme 3: Plausible mechanisms for reaction of hydroxamoyl chlorides 2 with imidazolyl enamines 1a,b.
  
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9. Figure 5: Geometries of enamine 1a appropriate to the calculated minima on the PES, and their relative free e...
  
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10. Scheme 4: Calculated pathways for the formation of experimentally observed 3a, regioisomer 7 and isoxazoline 8...
  
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11. Figure 6: Structures of the localized transition states. Lengths of the forming bonds are given in Å.
  
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12. Figure 7: Summary of the calculated pathways of the cycloaddition reaction between enamine 1a and benzonitril...
  
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13. Figure 8: Isosurface plots of the HOMO of enamine 1a_1 (bottom) and the LUMO of nitrile oxide 6 (top) in the ...
  
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