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Title of article :
exo-Selective inverse-electron-demand hetero Diels–Alder reactions of norbornene with 5-benzylidine-2-arylimino-3-aryl-thiazolidine-4-thiones at room temperature
Author/Authors :
Sule Erol، نويسنده , , Ilknur Dogan، نويسنده ,
Issue Information :
هفته نامه با شماره پیاپی سال 2013
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Abstract :
2-Arylimino-3-aryl-thiazolidine-4-thiones were synthesized from the corresponding thiazolidine-4-ones using Lawessonʹs reagent (LR) and converted into 5-benzylidine-2-arylimino-3-aryl-thiazolidine-4-thiones by reaction with benzaldehyde, which were then used as heterodienes in the inverse-electron-demand hetero Diels–Alder cycloadditions with norbornene as a dienophile at 25 °C. The reactions with norbornene were found to proceed with 100% exo-selectivity as determined by NMR experiments. The hetero Diels–Alder reactions with axially chiral heterodienes with ΔG#>116 kJ/mol showed kinetic atroposelectivities up to 11:1. However, the products were found to equilibrate, as revealed by the 97.1 kJ/mol barrier to hindered rotation of the most sterically hindered product, to produce 2:1 diastereoselectivities after the 24 h reaction time.
Keywords :
Bioconjugation , Inverse-electron-demand hetero Diels–Alder reaction , exo-Selectivity , Thiadiene , Norbornene , Atroposelectivity
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