Dynamic 1H NMR Study Around the Carbon–Carbon Double Bonds and Carbon–Carbon Single Bonds in a Particular Phosphorous Ylide and 2,5-Dihydro-5,5-Diaryl-2-Thio-1H-Imidazoles

Journal of Physical Chemistry & Eleectrochemistry

مقاله 6، دوره 2، شماره 2، خرداد و تیر 2014، صفحه 145-148   

نوع مقاله: Research Paper

تاریخ دریافت: 20 مهر 1392،  تاریخ پذیرش: 20 مهر 1392 

چکیده

Stable crystalline phosphorus ylides are obtained in excellent yields from the 1:1:1 addition reaction
between hydantoins or thiohydantoins and dialkyl acetylenedicarboxylates in the presence of
triphenylphosphine. These phosphoranes undergo smooth intramolecular Wittig reaction followed
by an electrocyclic ring opening to produce dialkyl (E)-2-(2,5-dihydro-5,5-diaryl-2-thioxo-1H-imidazol-
4-yl)fumarates and 2,5-Dihydro-5,5-diaryl-2-thio-1H-imidazoles in good yields. Dynamic
effects were observed in the 1H NMR spectra of these compounds and were attributed to restricted
rotation around the Carbon-Carbon single bonds. Rotational energy barrier (ΔG#) for their interconversion
process of rotational isomers equals to (68.2 and 71.7) ± 2 kJ mol-1.

کلیدواژه‌ها

Dynamic 1H NMR؛ Acetylenic ester؛ Restricted rotation؛ Triphenylphosphine