The assignment of the 1H and the 13C NMR chemical shifts of N-phenyl-2,4-dimethylbuta-1,3-diene-1,4-sultam

The assignment of the signals in the ¹³C and ¹H NMR spectra of N-phenyl-2,4-dimethylbuta-1,3-diene-1,4-sultam is difficult for the signal pairs C-2 and C-4, C-1 and C-3, (C-1)? H, (C-2)? CH₃ and (C-4)? CH₃. The ¹³C NMR spectrum recorded under gated decoupling conditions provide long-range couplings which make possible an unambiguous assignment of the ¹³C NMR signal pairs. Application of the ¹H CW off-resonance decoupling technique in recording the ¹³C NMR spectra enables the assignment information from the ¹³C NMR spectrum to be transferred to the ¹H NMR spectrum.