One-bond and long-range coupling constants of substituted 2-cyanopyridines. GIAO/DFT calculations of proton and carbon chemical shifts and coupling constants

Abstract

The magnitude of one bond and long-range coupling constants ((n)J(HH) and (n)J(CH)) in isomeric cyanopyridines-(1, 2, 3), methyl-(4, 5, 6, 7), 3-ethyl-(8), chloro-(9), 3-bromo-(10), acetyl-(11, 12), 5-ethoxycarbonyl-(13) and 4-(4'-pyridyl)-(14) derivatives of 2-cyanopyridines were determined in CDCl3. The Density Functional Theory/Gauge Including Atomic Orbitals (GIAO/DFT) calculation was employed for the estimation of proton or carbon chemical shifts and coupling constants ((n)J(HH) and (n)J(CH)) and the calculated NMR data compared with the experimental NMR data. The experimental values of (n)J(HH) and (n)J(CH) in derivatives of 2-cyanopyridines 1-14 are discussed with respect to the corresponding data in previously reported compounds and compared with values obtained from GIAO/DFT calculations and iterative simulation using gNMR software. Assignments of proton and carbon chemical shifts were achieved using one- and two-dimensional NMR techniques, such as 1D NOE difference, COSY, long-range COSY, gHMBC and gHMQC