Studies on the Nuclear Magnetic Resonance Spectra of (E)-1-Aryl-3-(2- and 3-thienyl)-2-propenones and Unique Observation of ⁴J and ⁵J Coupling in Their ¹H-¹H COSY

Studies on the Nuclear Magnetic Resonance Spectra of (E)-1-Aryl-3-(2- and 3-thienyl)-2-propenones and Unique Observation of ⁴J and ⁵J Coupling in Their ¹H-¹H COSY

$^1H$ and $^{13}C$ NMR spectra of series of (E)-1-aryl-(2- and 3-thienyl)-2-propenones, that are aldol condensation products between 2- and 3-thiophenecarbaldehydes and m- and p-substituted acetophenones, were examined to make complete assignments of the chemical shifts. Long range couplings, $^4J$ and $^5J$, are observed in the $^1H-^1H$ COSY of both 2- and 3-thienyl compounds, which makes the elucidation of the conformation in solution possible. In contrast, the 2-furyl analogue shows the long range coupling phenomena, but the 3-furyl and phenyl analogues do not show similar phenomena.