Correlation of substituted aromatic β -diketones' characteristic...

Research article

Received: 6 May 2013 Revised: 23 July 2013 Accepted: 23 July 2013 Published online in Wiley Online Library: 23 August 2013

(wileyonlinelibrary.com) DOI 10.1002/mrc.4001

Correlation of substituted aromatic β-diketones’characteristic protons chemical shifts withHammett substituent constantsJan Zawadiak and Marek Mrzyczek*

Influence of dibenzoylmethane’s substituents in meta and para positions on chemical shift values of tautomers’ characteristicprotons was investigated in four solvents with 1H NMR spectroscopy: acetone-d6, benzene-d6, CDCl3 and deuterated dimethylsulfoxide (DMSO-d6). It was proved that the influence of substituents on chemical shifts strongly depends on the kind of thesolvent; the greatest changes were observed in benzene-d6 and the smallest in CDCl3. In acetone-d6 and DMSO-d6, theinfluence of substituents on chemical shifts is similar and the most regular. It allowed a fair correlation of chemical shifts ofpara-substituted dibenzoylmethane derivatives’ characteristic protons with Hammett substituent constants in these solvents.In CDCl3, characteristic protons’ chemical shifts were near 1H NMR spectroscopy measurement error limits, and, therefore,correlation with Hammett substituent constants in this solvent was unsatisfactory. In benzene, although the changes ofchemical shifts are the most evident, the changes are also the most irregular, and, therefore, correlation in this solvent failedcompletely. Results ofmeta-substituted derivatives were much more irregular, and their correlation with Hammett substituentconstants was poor in all investigated solvents. Copyright © 2013 John Wiley & Sons, Ltd.

Keywords: NMR; 1H; 1,3-diketones; tautomerism; Hammett substituent constants; correlation

* Correspondence to: Marek Mrzyczek, Faculty of Chemistry, Silesian Universityof Technology, Krzywoustego 4, 44-100 Gliwice, Poland. E-mail: [email protected]

Faculty of Chemistry, Silesian University of Technology, Krzywoustego 4, 44-100 Gliwice, Poland

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Introduction

Dibenzoylmethane (DBM) is the simplest example of aromaticβ-diketones. DBM and its derivatives have many applications,of which adaptation as UV-A sunscreen is but one example.[1]

Aromatic β-diketones have also found application in the sepa-ration and spectrophotometric identification of f-blockmetals.[2] Recent research indicates that these compoundshave antitumor activity.[3] Specific location of carbonyl groupsallows them to form two tautomeric structures (Fig. 1).

Dibenzoylmethane exists mainly as enol tautomer, becausethis structure is stabilized by the formation of intramolecularhydrogen bonds.[4] Keto-enol tautomerism of DBM derivativeshas seldom been investigated, and our recent research provedthat it is difficult to determine the straightforward influence ofsubstituents in aromatic rings of DBM and its keto-enol tauto-meric equilibrium constant.[5]

One of the commonly used methods in the research of tauto-meric phenomena is 1H NMR spectroscopy,[6] which allows thecalculation of particular tautomeric concentrations from peakintegrals of characteristic proton signals. Hydroxyl proton peaksare often broad, and their integrals can contain large measuringerrors. Therefore, to calculate tautomeric content, it is better touse integrals from enol methine protons. Signals of this protonhave chemical shift values of ~6.8 (in relation to TMS) and inthe case of some derivatives can be hidden by signals fromaromatic protons. Chemical shifts of keto-tautomer methyleneprotons (COCH2CO) have values of ~4.6 ppm (in relation toTMS) where no other signals are present. However, in mostaromatic β-diketones, because of the prevailing content of theenol tautomer, diketonic tautomer methylene protons signalsare very weak and can be difficult to identify.

Magn. Reson. Chem. 2013, 51, 689–694

Determination of the relation between the kind of substitu-ent in aromatic rings and chemical shift values of characteristicprotons would allow prediction of the location of characteristicprotons’ signals in NMR spectra and, therefore, would simplifythe calculation of keto-enol tautomeric equilibrium constantsin various solvents by NMR spectroscopy.

So far, detailed studies concerning NMR spectroscopy andketo-enol tautomerism of β-diketones were carried out onvarious groups of compounds: curcuminoids,[7] β-diketoneswith trifluoromethyl[8] or alkyl groups,[9] where DBM was usuallythe only aromatic β-diketone. Moreover, in all of these studies,NMR spectroscopy was only a tool to calculate the tautomers’content. There is a lack of reliable research on DBM and itsderivatives’ spectra, which could allow determination of theinfluence of substituents in aromatic ring on the chemical shiftsof tautomers’ protons.

Results

We have synthesized DBM and its 17 derivatives with substituents inmeta and para positions of the aromatic rings (Fig. 2, Table 1).

We have collected 1H NMR spectra of all the synthesizedβ-diketones in the following solvents: benzene-d6, CDCl3,acetone-d6 and deuterated dimethyl sulfoxide (DMSO-d6).

Copyright © 2013 John Wiley & Sons, Ltd.

Figure 1. Keto-enol tautomerism of aromatic β-diketones.

Table 1. Synthesized derivatives of dibenzoylmethane

Diketone 1R 2R

DBM –H –H

1 –OCH3 –H

2 –Cl –H

3 –Br –H

4 –CH3 –H

5 –F –H

6 –NO2 –H

7 –C(CH3)3 –H

8 –COOCH3 –H

9 –COOH –H

10 –OH –H

11 –NHAc –H

12 –H –OCH3

13 –H –Cl

14 –H –F

15 –H –NO2

16 –H –COOCH3

17 –H –COOH

Figure 2. Structure of synthesized β-diketones.

J. Zawadiak and M. Mrzyczek

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Meticulous analysis of DBM derivative spectra allowed us to corre-late values of characteristic protons’ chemical shifts with Hammettsubstituent constants. Chemical shifts of tautomer protons can befound in Tables 2–5. Graphs of chemical shift dependence onHammett substituent constants are presented in Figs 3–5.On the basis of obtained results, we can assume that correla-

tion between chemical shifts of characteristic protons ofsubstituted DBM derivatives and Hammett substituent constantshas a linear form. Therefore, the chemical shift value equationshould have the following formula:

δS;X ¼ δS;H þ aS·σX

where δS,X is the chemical shift of X-substituted DBM derivative inthe ‘S’ solvent, δS,H the chemical shift of DBM in the S solvent, aSthe directional coefficient in the S solvent and σX the Hammettsubstituent constant of the ‘X’ substituent.[10]

From the NMR spectral analysis of the aforementionedcompounds, we have calculated the directional coefficients (aS)and coefficients of determination (r2) from linear regressionequations. These were obtained with Microsoft Excel 2010 fromfunctions where chemical shifts values were ordinates andHammett substituent constants were abscissas. We have defined24 equations for chemical shifts of DBM derivatives’ characteristic

For (C=O)CH=C–OH

para

Equation r2 Δxmax

δA = 17.27� 0.374 ·σX 0.969 0.05

δB = 17.75� 0.517 ·σX 0.721 0.26

δC = 16.89� 0.265 ·σX 0.944 0.05

δD = 17.21� 0.427 ·σX 0.969 0.05

For (C=O)CH=C–OH

para

Equation r2 Δxmax

δA = 7.25 + 0.210 ·σX 0.971 0.02

δB = 6.59� 0.262 ·σX 0.646 0.10

δC = 6.84� 0.086 ·σX 0.555 0.04

δD = 7.33� 0.210 ·σX 0.935 0.04

For (C=O)CH2(C=O)

para

Equation r2 Δxmax

δA = 4.80 + 0.211 ·σX 0.970 0.02

δB = 4.09� 0.239 ·σX 0.561 0.17

δC = 4.62� 0.086 ·σX 0.767 0.03

δD = 4.85� 0.199 ·σX 0.909 0.04

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protons in various solvents (A, acetone-d6; B, benzene-d6; C,CDCl3; D, DMSO-d6).

On the basis of the aforementioned equations, we canconclude that NMR signals coming from hydroxyl protons arethe most sensitive to the influence of substituent (directionalcoefficients from 0.221 to 0.517). Signals from the rest of theprotons are less sensitive, especially in chloroform, where theyhave almost constant value. Generally, we can assume that theinfluence of various solvents on the magnitude of change inchemical shift caused by a substituent is the following: benzene> acetone≈DMSO> chloroform.For the derivatives with substituents in the meta position, we

obtained equations with low values of coefficients of determi-nation for all three characteristic protons in all solvents except

meta

Equation r2 Δxmax

δA = 17.27� 0.282 ·σX 0.723 0.07

δB = 17.77� 0.551 ·σX 0.737 0.11

δC = 16.89� 0.221 ·σX 0.756 0.05

δD= 17.21� 0.313 ·σX 0.760 0.10

meta

Equation r2 Δxmax

δA = 7.24 + 0.286 ·σX 0.921 0.10

δB = 6.65� 0.308 ·σX 0.352 0.12

δC = 6.84 + 0.088 ·σX 0.183 0.07

δD = 7.33+ 0.235 ·σX 0.871 0.07

meta

Equation r2 Δxmax

δA = 4.81 + 0.263 ·σX 0.897 0.11

δB = 4.13� 0.268 ·σX 0.300 0.17

δC = 4.62 + 0.126 ·σX 0.436 0.07

δD = 4.86+ 0.217 ·σX 0.848 0.09

n Wiley & Sons, Ltd. Magn. Reson. Chem. 2013, 51, 689–694

Table 2. Tautomer protons chemical shifts of synthesized com-pounds in acetone-d6

Diketone (C¼O)CH2(C=O) (C¼O)CH=C–OH (C¼O)CH=C–OH Hammettsubstituentconstant σ

DBM 4.828 7.264 17.270 0

1 4.748 7.198 17.413 �0.27

2 4.844 7.289 17.163 0.23

3 4.839 7.287 17.155 0.23

4 4.777 7.228 17.311 �0.17

5 4.816 —a 17.248 0.06

6 4.973 7.418 16.996 0.78

7 4.778 7.221 17.300 �0.20

8 4.899 7.339 17.099 0.50

9 4.910 7.361 17.113 0.45

10 4.712 7.155 17.435 �0.37

11 4.756 7.206 17.356 �0.15

12 4.819 7.257 17.250 0.12

13 4.907 7.347 17.100 0.37

14 4.867 7.309 17.126 0.34

15 4.998 7.454 17.079 0.71

16 4.917 7.339 17.195 0.37

17 4.928 7.363 17.204 0.37

aCharacteristic signal of enol tautomer’s proton was covered.

Table 3. Tautomer protons chemical shifts of synthesized com-pounds in benzene-d6


DBM 4.100 6.610 17.740 0

1 4.160 6.650 18.000 �0.27

2 3.979 6.432 17.572 0.23

3 3.964 6.425 17.565 0.23

4 4.143 6.665 17.834 �0.17

5 3.971 6.645 17.978 0.06

6 3.919 6.358 17.306 0.78

7 4.189 6.731 17.874 �0.20

8 4.029 6.522 17.512 0.50

9 4.008 6.498 17.512 0.45

10 4.106 6.581 17.718 �0.37

11 4.299 6.639 17.878 �0.15

12 4.137 6.681 17.783 0.12

13 3.927 6.406 17.475 0.37

14 3.963 6.434 17.497 0.34

15 3.927 6.432 17.395 0.71

16 4.053 6.646 17.657 0.37

17 4.207 6.609 17.603 0.37

Table 4. Tautomer protons chemical shifts of synthesized com-pounds in CDCl3

Diketone (C¼O)CH2(C=O) (C¼O)CH=C–OH (C¼O)CH¼C–OH Hammettsubstituentconstant σ

DBM 4.627 6.859 16.904 0

1 4.591 6.806 17.014 �0.27

2 4.611 6.817 16.836 0.23

3 4.606 6.818 16.819 0.23

4 4.611 6.842 16.931 �0.17

5 4.613 6.806 16.864 0.06

6 4.695 6.899 16.681 0.78

7 4.622 6.852 16.933 �0.20

8 4.666 6.900 16.790 0.50

9 4.680 6.909 16.747 0.45

10 4.589 6.793 16.960 �0.37

11 4.605 6.822 16.928 �0.15

12 4.626 6.845 16.856 0.12

13 4.617 6.819 16.763 0.37

14 4.622 6.824 16.778 0.34

15 4.711 6.912 16.742 0.71

16 4.684 6.909 16.835 0.37

17 4.709 6.933 16.828 0.37

Table 5. Tautomer protons chemical shifts of synthesized com-pounds in DMSO-d6


DBM 4.890 7.360 17.210 0

1 4.800 7.280 17.370 �0.27

2 4.889 7.373 17.102 0.23

3 4.881 7.375 17.094 0.23

4 4.827 7.313 17.252 �0.17

5 4.880 —a 17.157 0.06

6 5.000 7.487 16.881 0.78

7 4.835 7.302 17.248 �0.20

8 4.944 7.423 17.010 0.50

9 4.937 7.421 17.036 0.45

10 4.735 7.208 17.396 �0.37

11 4.793 7.273 17.294 �0.15

12 4.869 7.333 17.192 0.12

13 4.923 7.411 17.042 0.37

14 4.911 7.396 17.037 0.34

15 5.030 7.513 17.001 0.71

16 4.953 7.394 17.102 0.37

17 4.952 7.416 17.136 0.37

aCharacteristic signal of enol tautomer’s proton was covered.

Correlation of substituted aromatic β-diketones’ characteristic protons

691

for methine protons (C=O)CH=C–OH in acetone. For para-substituted derivatives, equations are much better determined,especially in DMSO and acetone, where r2> 0.9. In chloroform,determination is poor for the signals coming from carbon-bonded protons – influence of substituents on chemical shiftsof protons (C=O)CH2(C=O) and (C=O)CH=C–OH is very small(directional coefficient 0.086), and, therefore, changes causedby a substituent are within the NMR spectroscopy margin of

Magn. Reson. Chem. 2013, 51, 689–694 Copyright © 2013 John

error, which explains small values of r2. In the case of hydroxylproton signals, where the directional coefficient is muchhigher (0.265), the correlation is much better (r2 = 0.944). Inbenzene, the existence of the substituent causes the biggestdifference in chemical shift values, but is very irregular, sothe correlation in this solvent failed completely.

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Figure 3. Dependence of para-substituted dibenzoylmethane derivatives’hydroxyl proton chemical shift on Hammett substituent constant.

Figure 4. Dependence of para-substituted dibenzoylmethane derivatives’methine proton chemical shift on Hammett substituent constant.

Figure 5. Dependence of para-substituted dibenzoylmethane derivatives’methylene proton chemical shift on Hammett substituent constant.


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Conclusions

The influence of substituents in aromatic diketones on their tauto-meric characteristic proton chemical shift values was determinedin four solvents. Inmeta derivatives, influence of the substituent isquite irregular in all investigated solvents, and it is difficult tocorrelate the chemical shift values with Hammett substituentconstant values. In para derivatives, irregularity is observed in


benzene and chloroform (for carbon-bonded protons). In DMSOand acetone, NMR results can be sufficiently well correlated withHammett substituent constants. Taking into consideration thatthese solvents are commonly used in NMR spectroscopy, our re-sults and equations coming out of them might be used as amethod for prediction of the chemical shift values of DBM deriva-tives’ characteristic protons. The signals of these protons areessential for the investigation of keto-enol tautomerism phenom-ena. It is also important to note that these signals have similarchemical shift values to signals coming from aromatic rings, andtheir location in NMR spectra can be difficult to determine.

Experimental

All NMR spectra were collected on a Varian Unity Inova Plus300MHz spectrometer at 20 °C. The concentrations of diketoneswere 50 ± 5mmol/dm3. 1H NMR shifts are listed excepting thetautomeric protons. Synthesis of all compounds has beendescribed previously: DBM, 1, 12,[4] 2–7, 10, 11, 13–15,[5] 8, 9,16, and 17.[11]

1,3-Diphenylpropane-1,3-dione (DBM)

1H NMR (CDCl3), δ (ppm): 7.48 (t, J = 7.2 Hz, 4H, Ar–H), 7.55(t, J = 7.2 Hz, 2H, Ar–H), 7.99 (d, J = 6.9, 4H, Ar–H). 13C NMR(CDCl3), δ (ppm): 93.3 (C(OH)=CH–CO), 127.4, 128.9, 132.7,135.7 (Ar–C), 185.9 (CO). logε= 4.40, λmax = 342.4 nm, EtOH.C15H12O2: Calcd. C 80.34; H 5.39. Found: C 80.39; H 5.42.mp 77.3–78.2 °C. Yield: 80%.

1-(4′-Methoxyphenyl)-3-phenylpropane-1,3-dione (1)

1H NMR (CDCl3), δ (ppm): 3.89 (s, 3H, OCH3), 6.99 (d, J=9.0 Hz, 2H,Ar–H), 7.46–7.57 (m, 3H, Ar–H), 7.96–8.01 (m, 4H, Ar–H). 13C NMR(CDCl3), δ (ppm): 55.7 (OCH3), 92.6 (C(OH)=CH–CO), 114.2, 127.2,128.4, 128.9, 129.5, 132.4, 135.7, 163.4 (Ar–C), 184.2, 186.4 (CO).logε=4.53, λmax = 354.0 nm, EtOH. C16H14O3: Calcd. C 75.58; H5.55. Found: C 75.69; H 5.52. mp 130.4–131.5 °C. Yield: 75%.

1-(4′-Chlorophenyl)-3-phenylopropane-1,3-dione (2)

1H NMR (DMSO-d6), δ (ppm): 7.54–7.68 (m, 5H, Ar–H), 8.16–8.21(m, 4H, Ar–H). 13C NMR (DMSO-d6), δ (ppm): 93.4 (C(OH)=CH–CO), 99.5, 127.4, 128.9, 129.0, 129.3, 133.1, 134.4, 137.9 (Ar–C),184.0, 185.4 (CO). logε= 4.46, λmax = 347.8 nm, EtOH. C15H11O2Cl:Calcd. C 69.64; H 4.29. Found: C 69.70; H 4.20. mp 86.9–87.6 °C.Yield: 76%.

1-(4′-Bromophenyl)-3-phenylpropane-1,3-dione (3)

1H NMR (DMSO-d6), δ (ppm): 7.57 (t, J = 7.6 Hz, 2H, Ar–H),7.66 (t, J = 7.6 Hz, 1H, Ar–H), 7.78 (d, J = 8.4 Hz, 2H, Ar–H),8.12 (d, J = 8.4 Hz, 2H, Ar–H), 8.18 (d, J = 7.6 Hz, 2H, Ar–H).13C NMR (DMSO-d6), δ (ppm): 93.4 (C(OH)=CH–CO), 99.5,107.3, 121.0, 127.5, 128.9, 129.4, 131.9, 150.0 (Ar–C), 184.8,185.6 (CO). logε= 4.45, λmax = 347.8 nm, EtOH. C15H11O2Br:Calcd. C 59.43; H 3.66. Found: C 59.42; H 3.64. mp 93.1-93.8 °C. Yield: 60%.


Correlation of substituted aromatic β-diketones’ characteristic protons

693

1-(4′-Methylphenyl)-3-phenylpropane-1,3-dione (4)

1H NMR (DMSO-d6), δ (ppm): 2.40 (s, 3H, CH3), 7.37 (d, J=8.4Hz, 2H,Ar–H), 7.56 (t, J=7.5Hz, 2H, Ar–H), 7.64 (t, J=7.5Hz, 1H, Ar–H), 8.08(d, J=8.4Hz, 2H, Ar–H), 8.16 (d, J=7.5Hz, 2H, Ar–H). 13C NMR(DMSO-d6), δ (ppm): 21.3 (CH3), 92.9 (C(OH)=CH–CO), 99.5, 127.3,127.5, 128.8, 129.4, 132.9, 134.6, 155.8 (Ar–C), 184.6, 185.6 (CO).logε=4.43, λmax=347.6nm, EtOH. C16H14O2: Calcd. C 80.65; H 5.92.Found: C 80.68; H 5.89. mp 84.0–85.4 °C. Yield: 73%.

1-(4′-Fluorophenyl)-3-phenylpropane-1,3-dione (5)

1H NMR (CDCl3), δ (ppm): 7.17 (t, J= 8.4 Hz, 2H, Ar–H), 7.47–7.59(m, 3H, Ar–H), 7.97–8.04 (m, 4H, Ar–H). 13C NMR (CDCl3),δ (ppm): 92.8 (C(OH)=CH–CO), 100.0, 102.7, 103.4, 108.5, 127.2,128.7, 129.7, 169.0 (Ar–C), 172.7, 180.6 (CO). logε=4.45, λmax =353.4 nm, EtOH. C15H11O2F: Calcd. C 74.37; H 4.58. Found: C74.36; H 4.63. mp 118.7–120.7 °C. Yield: 73%.

1-(4′-Nitrophenyl)-3-phenylpropane-1,3-dione (6)

1H NMR (DMSO-d6), δ (ppm): 7.59 (t, J = 7.5 Hz, 2H, Ar–H),7.69 (t, J = 7.5 Hz, 1H, Ar–H), 8.21 (d, J = 7.5 Hz, 2H, Ar–H),8.34–8.42 (m, 4H, Ar–H). 13C NMR (DMSO-d6), δ (ppm): 94.9(C(OH)=CH–CO), 99.5, 123.8, 127.8, 128.7, 129.0, 133.6,134.5, 139.9 (Ar–C), 180.2, 181.1 (CO). logε= 4.38, λmax =356.6 nm, EtOH. C15H11NO4: Calcd. C 66.91; H 4.12. Found:C 66.93; H 4.09. mp 161.4–162.9 °C. Yield: 94%.

1-(4′-tert-Butylphenyl)-3-phenylpropane-1,3-dione (7)

1H NMR (CDCl3), δ (ppm): 1.37 (s, 9H, CH3), 7.47–7.58 (m, 5H,Ar–H), 7.94 (d, J = 8.4 Hz, 2H, Ar–H), 7.99 (d, J = 8.4 Hz, 2H, Ar–H). 13C NMR (CDCl3), δ (ppm): 31.1 (C(CH3)3), 35.1 (C(CH3)3),92.9 (C(OH)=CH–CO), 100.0, 102.8, 125.7, 127.1, 128.7, 132.3,149.1, 156.3 (Ar–C), 185.9, 187.5 (CO). logε= 4.43, λmax = 349.2nm, EtOH. C19H20O2: Calcd. C 81.40; H 7.19. Found: C 81.39;H 7.20. mp 95.9–97.7 °C. Yield: 77%.

Methyl 4-(3′-phenyl-3′-oxopropionyl)benzoate (8)

1H NMR (CDCl3), δ (ppm): 3.97 (s, 3H, –COOCH3), 7.51 (t, J= 7.35Hz,2H, Ar–H), 7.59 (t, J= 7.35Hz, 1H, Ar–H), 7.98-8.07(m, 4H, Ar–H),8.15 (d, J= 8.7 Hz, 2H, Ar–H). 13C NMR (CDCl3), δ (ppm): 52.4(COOCH3), 93.8 (C(OH)=CH–CO), 127.0, 127.3, 128.6, 129.8, 132.8,133.2, 135.4, 139.2 (Ar–C), 166.3 (COOCH3), 183.5, 187.1 (CO).logε= 4.32, λmax = 351.4 nm, EtOH. C17H14O4: Calcd. C 72.33; H5.00. Found: C 72.30; H 5.04. mp 123.2–124.1 °C. Yield: 45%.

4-(3′-Phenyl-3′-oxopropionyl)benzoic acid (9)

1H NMR (DMSO-d6), δ (ppm): 7.57 (t, J = 7.4 Hz, 2H, Ar–H),7.67 (t, J = 7.4 Hz, 1H, Ar–H), 8.08 (d, J = 8.4 Hz, 2H, Ar–H),8.19 (d, J = 7.4 Hz, 2H, Ar–H), 8.27 (d, J = 8.4 Hz, 2H, Ar–H),13.34 (br, 1H, COOH). 13C NMR (DMSO-d6), δ (ppm): 94.1(C(OH)=CH–CO), 127.5, 127.6, 128.9, 129.6, 133.3, 134.2,134.6, 138.1 (Ar–C), 166.6 (COOH), 183.1, 186.7 (CO). logε=4.40, λmax = 348.6 nm, EtOH. C16H12O4: Calcd. C 71.64; H4.51. Found: C 71.55; H 4.64. mp 235.0–235.4 °C. Yield: 67%.

1-(4′-Hydroxyphenyl)-3-phenylpropane-1,3-dione (10)

1H NMR (DMSO-d6), δ (ppm): 6.90 (d, J= 8.7 Hz, 2H, Ar–H), 7.54(t, J= 7.2 Hz, 2H, Ar–H), 7.61 (t, J= 7.2 Hz, 1H, Ar–H), 8.06 (d,

Magn. Reson. Chem. 2013, 51, 689–694 Copyright © 2013 John

J = 8.7 Hz, 2H, Ar–H), 8.12 (d, J= 7.2 Hz, 2H, Ar–H), 10.47 (br,1H, Ar–OH). 13C NMR (DMSO-d6), δ (ppm): 92.1 (C(OH)=CH–CO),99.6, 103.5, 115.6, 125.7, 127.1, 128.8, 130.1, 162.3 (Ar–C), 182.7,186.5 (CO). logε=4.44, λmax=357.4nm, EtOH. C15H12O3: Calcd. C74.99; H 5.03. Found: C 75.00; H 5.05. mp 156.2–158.0 °C. Yield: 59%.

Acetic acid 4-(3′-phenyl-3′-oxopropionyl)anilide (11)

1H NMR (DMSO-d6), δ (ppm): 2.09 (s, 3H, NHCOCH3), 7.55 (t, J=7.2Hz,2H, Ar–H), 7.63 (t, J=7.2Hz, 1H, Ar–H), 7.76 (d, J=9.0Hz, 2H, Ar–H),8.12–8.15 (m, 4H, Ar–H), 10.32 (br, 1H, NHCOCH3).

13C NMR (DMSO-d6), δ (ppm): 24.2 (NHCOCH3), 84.7, either 92.5 or 93.8 (C(OH)=CH–CO),84.7, either 93.8 or 92.5, 115.3, 118.4, 127.2, 128.8, 134.6, 160.7 (Ar–C),164.0 (NHCOCH3), 184.7, 186.2 (CO). logε=4.54, λmax=360.0nm,EtOH. C17H15NO3: Calcd. C 72.58; H 5.37. Found: C 72.63; H 5.31.mp 159.4–161.5 °C. Yield: 54%.

1-(3′-Methoxyphenyl)-3-phenylpropane-1,3-dione (12)

1H NMR (CDCl3), δ (ppm): 3.89 (s, 3H, OCH3), 7.08–7.12 (m, 1H,Ar–H), 7.40 (t, J=7.5Hz, 1H, Ar–H), 7.47–7.59 (m, 5H, Ar–H),7.97–8.01 (m, 2H, Ar–H). 13C NMR (CDCl3), δ (ppm): 55.7 (OCH3),93.6 (C(OH)=CH–CO), 112.2, 118.8, 119.8, 127.4, 128.9, 129.9,132.7, 135.7, 137.3, 160.1 (Ar–C), 185.6, 186.1 (CO). logε=4.38,λmax =349.2nm, EtOH. C16H14O3: Calcd. C 75.58; H 5.55. Found:C 75.53; H 5.37. mp 59.2–60.4 °C. Yield: 69%.

1-(3′-Chlorophenyl)-3-phenylpropane-1,3-dione (13)

1H NMR (CDCl3), δ (ppm): 7.40–7.60 (m, 5H, Ar–H), 7.86 (d, J=7.8 Hz,1H, Ar–H), 7.95–8.01 (m, 3H, Ar–H). 13C NMR (CDCl3), δ (ppm):93.3 (C(OH)=CH–CO), 100.0, 102.7, 125.2, 127.2, 128.7, 130.0,132.3, 132.7, 134.9, 165.8 (Ar–C), 184.1, 184.2 (CO). logε= 4.40,λmax = 345.6 nm, EtOH. C15H11O2Cl: Calcd. C 69.64; H 4.29.Found: C 69.61; H 4.27. mp 69.3–70.4 °C. Yield: 68%.

1-(3′-Fluorophenyl)-3-phenylpropane-1,3-dione (14)

1H NMR (CDCl3), δ (ppm): 7.25 (t, J= 8.4Hz, 1H, Ar–H), 7.43–7.60(m, 4H, Ar–H), 7.68 (d, J= 8.7 Hz, 1H, Ar–H), 7.77 (d, J= 7.8 Hz,1H, Ar–H), 7.99 (d, J=7.8 Hz, 2H, Ar–H). 13C NMR (CDCl3), δ(ppm): 93.3 (C(OH)=CH–CO), 100.0, 113.9, 114.2, 119.1, 119.5,122.7, 127.3, 128.7, 130.2, 132.7 (Ar–C), 184.1, 186.1 (CO). logε=4.35, λmax = 345.0 nm, EtOH. C15H11O2F: Calcd. C 74.37; H 4.58.Found: C 74.35; H 4.60. mp 85.5–86.4 °C. Yield: 65%.

1-(3′-Nitrophenyl)-3-phenylpropane-1,3-dione (15)

1H NMR (DMSO-d6), δ (ppm): 7.57 (t, J= 7.5 Hz, 2H, Ar–H), 7.67(t, J= 7.5 Hz, 1H, Ar–H), 7.85 (t, J= 7.8Hz, 1H, Ar–H), 8.21(d, J= 7.5Hz, 2H, Ar–H), 8.45 (d, J= 7.8 Hz, 1H, Ar–H), 8.60(d, J= 7.8 Hz, 1H, Ar–H), 8.86 (s, 1H, Ar–H). 13C NMR (DMSO-d6),δ (ppm): 94.0 (C(OH)=CH–CO), 121.8, 127.1, 127.7, 128.9, 130.5,133.4, 133.5, 136.1, 142.9, 166.2, (Ar–C), 185.3, 185.5 (CO). logε=4.34, λmax = 342.4 nm, EtOH. C15H11NO4: Calcd. C 66.91; H 4.12.Found: C 66.97; H 4.08. mp 138.3–140.1 °C. Yield: 63%.

Methyl 3-(3′-phenyl-3′-oxopropionyl)benzoate (16)

1H NMR (CDCl3), δ (ppm): 3.99 (s, 3H, COOCH3), 7.48–7.63 (m, 4H,Ar–H), 8.02 (d, J= 7.0Hz, 2H, Ar–H), 8.22 (t, J= 7.0Hz, 2H, Ar–H),8.63 (s, 1H, Ar–H). 13C NMR (CDCl3), δ (ppm): 52.7 (COOCH3),93.5 (C(OH)=CH–CO), 127.5, 128.5, 129.0, 129.2, 131.0, 131.7,

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132.9, 133.4, 135.5, 136.2 (Ar–C), 166.6 (COOCH3), 184.7, 186.5(CO). logε= 4.38, λmax = 342.4 nm, EtOH. C17H14O4: Calcd. C72.33; H 5.00. Found: C 72.15; H 5.09. mp 82.4–83.2 °C. Yield: 42%.

3-(3′-Phenyl-3′-oxopropionyl)benzoic acid (17)

1H NMR (DMSO-d6), δ (ppm): 7.57 (t, J=7.4Hz, 2H, Ar–H), 7.67(t, J=7.4Hz, 1H, Ar–H), 8.08 (d, J=8.4Hz, 2H, Ar–H), 8.19(d, J=7.4Hz, 2H, Ar–H), 8.27 (d, J=8.4Hz, 2H, Ar–H), 13.34 (br, 1H,COOH). 13C NMR (DMSO-d6), δ (ppm): 94.1 (C(OH)=CH–CO), 127.5,127.6, 128.9, 129.6, 133.3, 134.2, 134.6, 138.1 (Ar–C), 166.6 (COOH),183.1, 186.7 (CO). logε=4.40, λmax=348.6nm, EtOH. C16H12O4: Calcd.C 71.64; H 4.51. Found: C 71.55; H 4.64. mp 235.0–235.4 °C. Yield: 67%.

Acknowledgement

This work was supported by the European Community from theEuropean Social Fund within the RFSD2 project.


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