NMR spectra of Δ³‐ and Δ⁴‐pyrrolin‐2‐one

Abstract

Abstract The spectra of Δ 3 ‐ and Δ 4 ‐pyrrolin‐2‐one were analysed and the sign of all the coupling constants determined by tickling and triple resonance experiments. A positive allylic interaction ( J xz in 2 ) is reported and four‐bond couplings are discussed in particular. Deuterium exchange affords evidence for the tautomeric equilibrium between 1 and 2 .