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

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 Csp2NCH2peaks 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. © 2014 Elsevier B.V. All rights reserved.