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Title: Synthesis and NMR spectral study of some 5-aryl-3-methylcyclohex-2-enones and 5<i>r</i>-aryl-3<i>t</i>-cyano-3<i>c</i>-methylcyclohexanones
Authors: Kamatchi, S
Mohan, R T Sabapathy
Gomathi, R
Pandiarajan, K
Keywords: Cyclohex-2-enones
<sup>1</sup>H NMR
<sup>13</sup>C NMR
Issue Date: Apr-2009
Publisher: CSIR
Abstract: <smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="metricconverter"> Eight 5-aryl-3-methylcyclohex-2-enones <b>2a-h</b> (Ar = C<sub>6</sub>H<sub>5</sub>, <i>p</i>-ClC<sub>6</sub>H<sub>4</sub>, <i>p</i>-MeOC<sub>6</sub>H<sub>4,</sub> <i>p</i>-O<sub>2</sub>NC<sub>6</sub>H<sub>4</sub>, <i>p</i>-MeC<sub>6</sub>H<sub>4</sub>, <i>p</i>-FC<sub>6</sub>H<sub>4</sub>, <i>p</i>-Me<sub>2</sub>­NC<sub>6</sub>H<sub>4</sub> or <i>m</i>-O<sub>2</sub>NC<sub>6</sub>H<sub>4</sub>) and seven 5<i>r</i>-aryl-3<i>t</i>-cyano-3<i>c</i>-methylcyclohexanones <b>3a-c</b> and <b>3e-h</b> (Ar = C<sub>6</sub>H<sub>5</sub>, <i>p</i>-ClC<sub>6</sub>H<sub>4</sub>, <i>p</i>-MeOC<sub>6</sub>H<sub>4,</sub> <i>p</i>-MeC<sub>6</sub>H<sub>4</sub>, <i>p</i>-FC<sub>6</sub>H<sub>4</sub>, <i>p</i>-Me<sub>2</sub>­NC<sub>6</sub>H<sub>4</sub> or <i>m</i>-O<sub>2</sub>NC<sub>6</sub>H<sub>4</sub>) have been synthesized and characterised by <sup>1</sup>H and <sup>13</sup>C NMR spectra. For <b>2a</b> (Ar = C<sub>6</sub>H<sub>5</sub>) SEFT and HMBC spectra have been recorded. For <b>2e</b> (Ar = <i>p</i>-MeC<sub>6</sub>H<sub>4</sub>) HSQC and HMBC spectra have been recorded. For <b>3a</b> (Ar = C<sub>6</sub>H<sub>­5</sub>) HOMOCOSY, NOESY, HSQC and SEFT spectra have been recorded. Analysis of these spectra suggests that cyclohex-2-enones adopt sofa conformation with one of the methylene protons at C-4 and C-6 <i>anti</i> to H-5 and the other methylene proton <i>gauche</i> to H-5. The effect of the phenyl and methyl groups on the chemical shifts of protons and carbons in cyclohexenone ring are discussed. The cyanocyclohexanones adopt chair conformation with axial orientation of cyano group and equatorial orientations of the methyl and phenyl groups. The probable values for the proton chemical shifts of the various protons in the cyclohexanone ring of <i>cis</i>-3-methyl-5-phenylcyclohexanone <b>6</b> have been computed from the observed proton chemical shifts of <b>3a</b> and the known effects of axial cyano group. The possible values for the <sup>13</sup>C chemical shifts of the cyclohexanone ring carbons in <b>6</b> have been computed from the <sup>13</sup>C chemical shifts of cyclohexanone and known effects of phenyl and methyl groups. Comparison of these values with the chemical shifts of protons and carbons in <b>2a</b> suggests that the double bond at C-2 influences the <sup>1</sup>H chemical shifts by polarization, magnetic anisotropy and electronegativity effects and the <sup>13</sup>C chemical shifts by polarization and electronegativity effects. </smarttagtype>
Description: 553-562
ISSN: 0376-4699
Appears in Collections:IJC-B Vol.48B(04) [April 2009]

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