Abstract
The authors concluded in this paper that the proton of the ethenylene with the chemical shift at higher magnetic field is located next to sulfur referring the experimental results reported by Klemm et al. with 4-nitro-thienopyridine derivatives. However it is notable that assignments of H-2 and H-3 may be reversed. In cases of 13C NMR, the results from HSQC indicate the carbons directly attaching to hydrogen atoms and those from HMBS indicate long range coupling in 2-3 carbon sequences. Especially, even in 1D spectroscopy, the carbons locating at distinctively low magnetic field, around 161 ppm for C-9a and 145-147 ppm for C-8a, showed good match with the results previously reported and are key to determine the baseline structure of the products. Authors finally conclude that a 4-cyanothienoquinoline base-structure reasonably explains the experimental results obtained without any contradiction and that the chemical structure of Product A and B.
