Santos, Clementina M.M.Silva, ArturJeko, JózsefLévai, Albert2013-03-152013-03-152012Santos, Clementina M. M.; Silva, Artur; Jeko, J.; Levai, A. (2012). Synthesis and structure elucidation of novel pyrazolyl-2-pyrazolines obtained by the reaction of 3-(3-aryl-3-oxopropenyl)chromen-4-ones with phenylhydrazine. ARKIVOC. ISSN 1551-7004. 5, p. 265-2811551-7004http://hdl.handle.net/10198/8272Novel 3-aryl-5-{4-[5-(2-hydroxyphenyl)-1-phenylpyrazolyl]}-2-pyrazolines 2a-g have been prepared by the treatment of 3-(3-aryl-3-oxopropenyl)chromen-4-ones 1a-g with phenylhydrazine in refluxing acetic acid. NMR studies on deuteriochloroform solutions of pyrazolyl-2-pyrazolines 2a-g at different temperatures showed that at room temperature a mixture of diastereomers are present. This diastereoselectivity arises from the combination of the pyrazoline C-4 stereocenter and two planar chiral subunits due to internal steric hindrance. The energy barriers of this steric hindrance were overcome in DMSO-d6 solutions at 60oC. The acetylation of some pyrazolyl-2-pyrazoline derivativess 2a-c,e helped to confirm the presence of the referred mixture of diastereomers.engChromonesPhenylhydrazineBispyrazoles4-Pyrazolyl-2-pyrazolinesDiastereomersPlanar chiralityNMR spectroscopyjournal article10.3998/ark.5550190.0013.522