X-ray diffraction and VT-NMR studies of (E)-3-(piperidinyl)-1-(2′-hydroxyphenyl)-prop-2-en-1-one

•(E)-Selective synthesis of 3-(piperidinyl)-1-(2′-hydroxyphenyl)-prop-2-en-1-one.•3D structure determination of the compound by X-ray diffraction.•Spectroscopic characterization of the compounds by 1D and 2D NMR.•Flexible rotation of the compound along the CN bond explained by VT-NMR studies.

A series of 1-aryl-3-(cyclicamino)-prop-2-en-1-one analogs was synthesized from commercial acetophenones in 2 or 3 steps. Compound 6, (E)-3-(piperidinyl)-1-(2′-hydroxyphenyl)-prop-2-en-1-one, exhibited the unique shape and intensity of the Csp2NCH2 peaks in the 1H and 13C NMR spectra. Variable temperature (VT) nuclear magnetic resonance (NMR) and X-ray diffraction (XRD) studies of 6 revealed that the piperidine ring has a lower energy barrier to rotation than the 5-membered pyrrolidine 9 due to the less effective π electron delocalization along the Csp2N bond.

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