Synthesis, NMR, X-ray crystallography and DFT studies of some regioisomers possessing imidazole heterocycles

Imidazole-containing heterocycles: Imidazopyridines, imidazopyrimidines can exist in several tautomeric forms. Their regioselectivities were determined for N-alkylations with 4-chlorobenzyl bromide under basic conditions (K2CO3) in DMF. We observed that, regioisomers were mainly formed as a mixture in this reaction and N-benzylation occurs at a higher ratio on six membered heterocycles. Their structural assignments were made with the use of two-dimensional H-1-H-1 NOE (Nuclear Overhauser Effect Spectroscopy, NOESY) and H-1-N-15 HMBC (Heteronuclear Multiple Bond Correlation) spectra. Further confirmation of the structure of 2c and 3c were obtained from X-ray crystallography. Experimental data was confirmed by Density Functional Theory (DFT) studies as well. (C) 2021 Elsevier B.V. All rights reserved.