A comparative study between para‐aminophenyl and ortho‐aminophenyl benzothiazoles using NMR and DFT calculations. (3rd June 2014)

• Record Type: Journal Article
• Authors: Pierens, G. K.; Venkatachalam, T. K.; Reutens, D.
• Is Part Of: Magnetic resonance in chemistry. Volume 52:Number 8(2014:Aug.)
• Page Start: 453
• Page End: 459
• Publication Date: 2014-06-03
• Subjects: Nuclear magnetic resonance spectroscopy -- Periodicals; Chemistry, Organic -- Periodicals; Magnetic resonance -- Periodicals; 538.36
• DOI: 10.1002/mrc.4088
• Languages: English
• ISSNs: 0749-1581

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <p> <italic>Ortho</italic>‐substituted and <italic>para</italic>‐substituted aminophenyl benzothiazoles were synthesised and characterised using NMR spectroscopy. A comparison of the proton chemical shift values reveals significant differences in the observed chemical shift values for the NH protons indicating the presence of a hydrogen bond in all <italic>ortho</italic>‐substituted compounds as compared to the <italic>para</italic> compounds. The presence of intramolecular hydrogen bond in the <italic>ortho</italic> amino substituted aminophenyl benzothiazole forces the molecule to be planar which may be an additional advantage in developing these compounds as Alzheimer's imaging agent because the binding to amyloid fibrils prefers planar compounds. The splitting pattern of the methylene proton next to the amino group also showed significant coupling to the amino proton consistent with the notion of the existence of slow exchange and hydrogen bond in the <italic>ortho</italic>‐substituted compounds. This is further verified by density functional theory calculations which yielded a near planar low energy conformer for all the <italic>o</italic>‐aminophenyl benzothiazoles and displayed a hydrogen bond from the amine proton to the nitrogen of the thiazole ring. A detailed analysis of the <sup>1</sup>H, <sup>13</sup>C and <sup>15</sup>N NMR chemical shifts and density functional theory calculated structures of the compounds are described. Copyright © 2014 John Wiley & Sons, Ltd.</p> </abstract>