Investigation of neighboring heteroatoms and coupling pathway effects on long-range coupling constants using LR-HSQMBC

LR-HSQMBC is one of the most recently developed NMR experiments for detection of long-range (ⁿ J _CH, n> 3) heteronulcear coupling, and for overcoming the challenges of structure elucidation of proton deficient molecules. To investigate the dependencies of long-range coupling constants on the neighboring heteroatoms and coupling pathway between proton and carbon nuclei, LR-HSQMBC was used to visualize ^{4 – 6} J _CH in molecules 1 – 4 below. To aid in the investigation, density functional theory (DFT) was used, and a comparison of the calculated and experimental long-range coupling constant values will be presented.