Exploiting natural abundance 13C–15N coupling as a method for identification of nitrogen heterocycles: practical use of the HCNMBC sequence

In this paper, we detail the results of ¹H–¹⁵N correlation data obtained via ¹³C–¹⁵N coupling at natural abundance on a number of classes of azoles including pyrazoles, imidazoles and triazoles. The experiment produces data that is highly complementary to direct ¹H–¹⁵N HMBC type correlations in that it can provide ¹⁵N chemical shift data for nitrogen that may not show up in the HMBC. This is particularly advantageous in the triazoles where ¹⁵N chemical shift can be diagnostic of regiochemistry. Because of the consistency in J_CN values among the azoles, the experiment produces distinctive correlation patterns that can be used for identification of regiochemistry. The experiment can also be used to directly measure ¹³C–¹⁵N coupling constants. Copyright © 2015 John Wiley & Sons, Ltd.