Assignments of the ¹H and ¹³C NMR spectra of pseudo‐symmetric heterocyles using the HMQC‐TOCSY experiment to differentiate overlapping spin systems

Abstract

Abstract The 1 H nmr spectra of phenanthro[9′,10′:4,5]thieno[2,3‐ c ]quinoline, benzo[ f ]phenanthro‐[9′,10′:4,5]thieno[2,3‐ c ]quinoline and benzo[ h ]phenanthro[9′,10′:4,5]thieno[2,3‐ c ]quinoline are highly congested. For each compound, all protons abide in an aromatic environment complicated by pseudo‐symmetric regions which result in multiple overlap of the different spin systems these molecules contain. We illustrate here the utility of the HMQC‐TOCSY experiment to identify spin systems when the proton spectrum is highly congested. To complete the assignment of the 1 H and 13 C nmr spectra of each compound the HMBC experiment is used to assign the quaternary carbons.