80223-13-8Relevant articles and documents
Substituent Effects in Heterocyclic Systems. 1H-NMR Study of Methyl 3,5-diaryloxazolium Iodides
Baumstark, Alfons L.,Dunams, Tambra
, p. 1113 - 1116 (2007/10/02)
Methyl 3-aryl-5-phenylisoxazolium iodides (I) and methyl 3-phenyl-5-arylisooxazolium iodides (II) were synthesized from the corresponding isoxazoles in moderate yields.The 1H-nmr chemical shifts for H-4, series I and II, and the quarternary methyl group series II were found to correlate with ?+ values.The rho value observed for H-4 series II was 3.3 times that observed in series I.The correlation observed in series I contrasts with the lack of(poor) correlations reported in the corresponding isoxazole and chalcone systems.The rho value observed in the correlationof the quarternary methyl group series II correlates well with an estimate based on methyl pyridinium salt data.The chemical shifts of the quarternary methyl group series I showed little or no variation.Swain-Lupton and DSP treatments did not show improved correlations over the single parameter results.Howewer, interpretation of these treatments reveals that similar processes are occuring in all three cases.The results for H-4 series I showed that the reduction of transmission of the substituent effect in series I compared to that in series II was essentially due to equal reduction of both inductive and resonance effects.The mechanism of transmission seems to differ only in degree and not type.