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 CDCl 3. 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.