Synthesis and structure elucidation of novel pyrazolyl-2-pyrazolines obtained by the reaction of 3-(3-aryl-3-oxopropenyl)chromen-4-ones with phenylhydrazine

Clementina M M Santos, Artur M S Silva, J. Jekó́, A. Lévai

Research output: Article

9 Citations (Scopus)

Abstract

Novel 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 60°C. The acetylation of some pyrazolyl-2-pyrazoline derivatives 2a-c,e helped to confirm the presence of the referred mixture of diastereomers.

Original languageEnglish
Pages (from-to)265-281
Number of pages17
JournalArkivoc
Volume2012
Issue number5
DOIs
Publication statusPublished - máj. 23 2012

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Acetylation
Energy barriers
Dimethyl Sulfoxide
Acetic Acid
Nuclear magnetic resonance
Derivatives
Temperature
phenylhydrazine

ASJC Scopus subject areas

  • Organic Chemistry

Cite this

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title = "Synthesis and structure elucidation of novel pyrazolyl-2-pyrazolines obtained by the reaction of 3-(3-aryl-3-oxopropenyl)chromen-4-ones with phenylhydrazine",
abstract = "Novel 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 60°C. The acetylation of some pyrazolyl-2-pyrazoline derivatives 2a-c,e helped to confirm the presence of the referred mixture of diastereomers.",
keywords = "4-Pyrazolyl-2-pyrazolines, Bispyrazoles, Chromones, Diastereomers, NMR spectroscopy, Phenylhydrazine, Planar chirality",
author = "Santos, {Clementina M M} and Silva, {Artur M S} and J. Jek{\'o}́ and A. L{\'e}vai",
year = "2012",
month = "5",
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doi = "10.3998/ark.5550190.0013.522",
language = "English",
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AU - Silva, Artur M S

AU - Jekó́, J.

AU - Lévai, A.

PY - 2012/5/23

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N2 - Novel 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 60°C. The acetylation of some pyrazolyl-2-pyrazoline derivatives 2a-c,e helped to confirm the presence of the referred mixture of diastereomers.

AB - Novel 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 60°C. The acetylation of some pyrazolyl-2-pyrazoline derivatives 2a-c,e helped to confirm the presence of the referred mixture of diastereomers.

KW - 4-Pyrazolyl-2-pyrazolines

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KW - Chromones

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KW - NMR spectroscopy

KW - Phenylhydrazine

KW - Planar chirality

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