Synthesis and Conformational Assignment of N-(E

Hindawi Publishing Corporation Journal of Spectroscopy Volume 2013, Article ID 197475, 12 pages http://dx.doi.org/10.1155/2013/197475

Research Article Synthesis and Conformational Assignment of N-(E)-Stilbenyloxymethylenecarbonyl-Substituted Hydrazones of Acetone and o-(m- and p-) Chloro- (nitro-) benzaldehydes by Means of 1H and 13C NMR Spectroscopy Przemysław Patorski, Elżbieta Wyrzykiewicz, and Grażyna Bartkowiak Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznań, Poland Correspondence should be addressed to Grażyna Bartkowiak; [email protected] Received 29 June 2012; Revised 17 October 2012; Accepted 31 October 2012 Academic Editor: Ozlem Oter Copyright © 2013 Przemysław Patorski et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Eighteen new N-(E)-stilbenyloxyalkylcarbonyl-substituted hydrazones of ortho- (meta- and para-) chloro- (nitro-) benzaldehydes 1–18 and two analogous hydrazones of acetone 19-20 were prepared. e stereochemical behavior of 1–18 in dimethyl-d6 sulfoxide solution has been studied by 1 H NMR and 13 C NMR techniques, using spectral data of 19 and 20 as supporting material. e E-geometrical isomers and cis-/trans-amide conformers have been found for these hydrazones. Energy barriers of isomers are reported.

1. Introduction e N-substituted hydrazones of aldehydes are of interest because of their biological and pharmacological activities [1– 5], as well as considerable chelating power with transition metals [6–9]. ey can be used in analytical chemistry to cover and analyze metals selectively as hydrazone complexes. Hydrazones of o-(m- and p-) chlorobenzaldehydes and o(m- and p-) nitrobenzaldehydes have been reported in the literature [10–13]. Chloro- and nitrobenzaldehydes are widely used as reagents for organic synthesis, chie�y as reactants for manufacturing pharmaceuticals, plastic additives, pesticides, dyes and metal �nishing agents. �or example, 2chlorobenzaldehyde is an intermediate for the optical brighteners production and �nds its application as the brightening agent for zinc plating, whereas 2-nitrobenzaldehyde is a substrate for indigo synthesis in the Baeyer-Drewson method [14] and easy removable protection group for many functionalities [15].

However, despite the many synthetic applications of substituted benzaldehydes, to the best of our knowledge no work has been published in the literature about the synthesis and physicochemical properties of N-(E)stilbenyloxyalkylcarbonyl substituted hydrazones of ortho(meta- and para-) chloro- and (nitro-) benzaldehydes. ese compounds, containing amide and hydrazone functions in their molecules, seemed to be suitable candidates for further chemical modi�cations and may be pharmacologically active and analytically useful. It ought to be pointed out that (E)stilbenes hydroxylated at one to �ve positions as well as their ethereal derivatives are produced by woody plants and exhibit a broad spectrum of biological activity [16–20]. We have previously reported the synthesis, physicochemical properties, as well as mass spectrometric study of N-(E)-stilbenyloxyalkylcarbonyl substituted hydrazones of o-(m- and p-) hydroxybenzaldehydes and 2-(3- and 4-) pyridinecarboxyaldehydes [21–26]. Our studies have been recently extended to N-(E)-stilbenyloxymethylenecarbonyl substituted hydrazones of o-(m- and p-) chlorobenzaldehydes

2

Journal of Spectroscopy T 1: Chemical and physical data of compounds 1–18.

Compound

Formula Mol. weight

1

C23 H19 N2 O2 Cl 390.60

75

194–5

0.48

2

C23 H19 N2 O2 Cl⋅1/2H2 O 399.60

53

191–3

0.52

3

C23 H19 N2 O2 Cl⋅2H2 O 426.64

49

207–9

0.64

4

C23 H19 N3 O4 401.14

61

188–190

0.76

43

232–4

0.60

64

192–5

0.42

41

190–2

0.58

C23 H18 N2 O2 Cl2 425.31

45

238–240

0.31

9

C23 H18 N2 O2 Cl2 425.31

62

208–10

0.43

10

C23 H18 N3 O4 Cl⋅1H2 O 453.88

49

190–2

0.65

11

C23 H18 N3 O4 Cl⋅1/2H2 O 444.63

56

201–4

0.53

12

C23 H18 N3 O4 Cl⋅1.5H2 O 462.56

39

215–17

0.43

13

C23 H18 N3 O4 Cl⋅1/2H2 O 444.63

35

209–11

0.55

14

C23 H18 N3 O4 Cl⋅1/2H2 O 444.63

67

260–2

0.7

15

C23 H18 N3 O4 Cl⋅1/2H2 O 444.63

66

208–10

0.43

16

C23 H18 N4 O6 446.41

53

228–31

0.69

17

C23 H18 N4 O6⋅1/2H2 O 455.41

65

263–5

0.38

18

C23 H18 N4 O6⋅2.5H2 O 491.43

73

245–8

0.10

5 6 7 8

C23 H19 N3 O4 ⋅1/2H2 O 410.66 C23 H19 N3 O4 ⋅H2 O 419.11

C23 H18 N2 O2 Cl2 ⋅1/2H2 O 434.31

Yield [%]

M.p. [○ C]

and o-(m- and p-) nitrobenzaldehydes 1–18. is paper deals with the synthesis and the investigation of the stereochemical behavior of these compounds in DMSO-d6 solution by means of 1 H and 13 C NMR spectroscopy.

2. Results and Discussion Treatment of the corresponding o-(m- and p-) chlorobenzaldehydes and o-(m- and p-) nitrobenzaldehydes with

𝑅𝑅𝑓𝑓 (TLC)

Elemental analyses Calculated (found) C

H

N

70.70 (70.59) 70.01 (70.08) 64.78 (64.94) 68.30 (68.49) 67.32 (67.59) 65.89 (65.56) 63.74 (63.87) 64.95 (64.96) 64.95 (64.87) 60.86 (61.08) 62.13 (62.58) 59.74 (60.14) 62.16 (62.48) 62.16 (62.36) 62.16 (62.02) 61.88 (61.63) 60.66 (60.94) 56.21 (56.18)

4.87 (4.91) 4.87 (4.80) 4.46 (4.40) 4.74 (4.85) 4.88 (5.07) 5.01 (4.93) 4.39 (4.40) 4.27 (4.26) 4.27 (4.35) 4.44 (4.73) 4.31 (4.65) 4.55 (4.83) 4.27 (4.13) 4.27 (4.47) 4.27 (4.16) 4.06 (4.21) 4.17 (4.22) 4.72 (4.71)

7.18 (7.09) 7.04 (7.05) 6.57 (6.50) 10.47 (10.32) 10.24 (10.15) 10.02 (9.96) 6.47 (6.54) 6.59 (6.57) 6.59 (6.38) 9.26 (9.17) 9.45 (9.18) 9.09 (9.31) 9.45 (9.60) 9.45 (9.48) 9.45 (9.60) 12.55 (12.58) 12.30 (12.20) 11.40 (11.16)

the hydrazides of (E)-stilbenyl-4-oxyacetic acid [(E)-4′ chlorostilbenyl-4-oxyacetic acid, (E)-4′ -nitrostilbenyl-4oxyacetic acid] in boiling absolute ethanol (or boiling DMF) afforded 1–18 (Figure 1). N-(E)-4′ -chlorostilbenyl4-oxymethylenecarbonyl and N-(E)-4′ -nitrostilbenyl-4oxymethylenecarbonyl substituted hydrazones of acetone 19 and 20 (Figure 2) as the reference compounds have been obtained similarly. e structures of compounds 1–18 were determined by examining their UV/Vis, IR, 1 H NMR and 13 C NMR spectra as well as elemental analyses (Tables 1, 2,

Journal of Spectroscopy

3 T 2: UV/Vis∗ and IR (KBr) data of compounds 1–18.

IR (cm−1 ) 𝛿𝛿–CH=CH– trans E

UV/Vis 𝜆𝜆max (lg 𝜀𝜀)

Compound 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

293.50 (4.61) 303.50 (4.60) 296.00 (4.70) 323.00 (4.55) 321.50 (4.51) 324.50 (4.63) 293.50 (4.61) 326.60 (4.46) 295.00 (4.65) 328.00 (4.58) 326.50 (4.53) 329.50 (4.66) 291.00 (4.45) 386.00 (4.35) 294.00 (4.52) 383.00 (4.38) 385.50 (4.38) 361.00 (4.44)

∗

952 967 960 953 966 963 958 962 958 970 966 962 966 962 967 966 966 970

e UV/Vis spectra of 1–3, 7–9, 13–15 were recorded in MeOH, e UV/Vis spectra of 4–6, 10–12, 16–18 were recorded in DMSO.

2

2

H

H

3

3 X2

1 3 X1

α

2

1

4

N O

N

1

4

α 5

6

5

4 6

O

5

6 X2 = o–Cl

10 X1 = Cl

X2 = o–NO2

2 X1 = H

X2 = m–Cl

11 X1 = Cl

X2 = m–NO2

3 X1 = H

X2 = p–Cl

12 X1 = Cl

X2 = p–NO2

4 X1 = H

X2 = o–NO2

13 X1 = NO2

X2 = o–Cl

5 X1 = H

X2 = m–NO2

14 X1 = NO2

X2 = m–Cl

6 X1 = H

X2 = p–NO2

15 X1 = NO2

X2 = p–Cl

7 X1 = Cl

1 X1 = H

X2 = o–Cl

16 X1 = NO2

X2 = o–NO2

8 X1 = Cl

X2 = m–Cl

17 X1 = NO2

X2 = m–NO2

9 X1 = Cl

X2 = p–Cl

18 X1 = NO2

X2 = p–NO2

F 1: e structures of compounds 1–18.

3, 4, 5, 6, 7, and 8), the respective data for compounds 19 and 20 have been collected in Tables 10, 11, and 12. e hydrazones 1–18 can exist as Z/E geometrical isomers about C=C bond of ethylene bridge in the stilbene part of the molecule, Z/E geometrical isomers about C=N bond of hydrazone moiety as well as cis/trans amide conformers (Figure 3).

Previously, we have demonstrated that N-(E)-stilbenyloxymethylenecarbonyl substituted hydrazones of o-(m- and p-) hydroxybenzaldehydes occurred as (E)-geometrical isomers about C=N bond in DMSO-d6 [24], as well as in the solid phase [23]. According to the literature hydrazones of o(m- and p-) nitrobenzaldehydes are essentially planar with E con�guration at the C=N double bond [10, 11], as well

4

Journal of Spectroscopy T 3: 1 H NMR data for compounds 1–9 (𝛿𝛿, ppm). –OCH2 – s, cis s, trans

–NH– s, cis s, trans

N=CH s, cis s, trans

Ar∗ m

1

5.20 4.72

11.87 11.82

8.41 8.77

8.06–6.95

2

5.20 4.72

11.74 —

8.09 8.33

7.82–6.94

3

5.18 4.71

11.69 11.67

8.02 8.34

7.77–6.94

4

5.17 4.73

11.92 11.91

8.39 8.75

8.16–6.95

5

5.23 4.75

11.88 —

8.15 8.53

8.27–6.95

6

5.23 4.75

12.40 11.93

8.29 8.31

8.36–6.87

7

5.20 4.72

11.87 11.81

8.41 8.76

8.37–6.72

8

5.20 4.71

11.73 —

8.00 8.33

7.81–6.95

9

5.18 4.71

11.71

8.02 8.34

7.77–6.82

Compund

∗Aromatic

ring protons.

T 4: 13 C NMR data of compounds 1–9—Part A (stilbene carbons), two values given for each carbon atom concern cis and trans conformers.

2 3

2

α

1

A

4 O

X1

4

1 2 3 4 5

C-1 137.33 137.26 137.33 137.26 137.34 137.28 137.33 137.27 137.15 137.08

6

137.15

7

132.98

8 9

131.47 131.39 133.39 132.94

N N

C

C-2,6 126.19 126.16 126.17 125.81 126.21 126.24 126.18 124.22 124.03 126.41 126.02 127.94 127.85 127.90 127.80 128.66

α

6

C-3,5

128.66 128.00 128.94 128.88 128.60 128.06

C-4 127.61 127.01 127.26 127.19 127.79 127.69 127.69 127.02

128.49

127.03

5

2

3

6

5

1

1 5

Compound

H

H

3

X2 4

B

O

6

128.64

128.49 127.63 127.10 126.39 126.16 127.93 127.84

127.62 127.52 136.38 136.31 136.37 136.29 136.38 136.31

C-𝛼𝛼 126.92 126.52 126.55 126.38 126.57 126.56 126.40 126.00 127.04 131.68 130.02 124.85 129.71

C-𝛼𝛼′ 129.85 127.98 129.60 129.81 128.00 127.86 127.85 127.78

C-1′ 129.90 129.86 129.90 129.81

127.83

129.77

127.92 127.81 126.95 125.26 125.81 125.21 125.23 124.89

129.91 129.70 129.82 129.67

C-2′ ,6′ 127.76 127.67 127.78 127.67 128.67 128.21 128.03 127.98 127.68 127.61 127.75 127.68 131.37 131.27 128.77 128.63

128.66

130.22

130.46 129.98

129.82

C-3′ ,5′ 114.99 114.79 114.95 114.79 114.97 114.78 114.96 114.72 114.81 114.61 114.82 114.66 115.04 114.84 114.87 114.82 115.00 114.83

C-4′ 157.91 157.38 157.84 154.40 157.94 157.42 157.87 157.40 157.70 157.18 157.67 157.18 158.09 157.56 158.11 157.56 158.12 157.60

Journal of Spectroscopy

5

T 5: 13 C NMR data of compounds 1–9—Part B; two values given for each carbon atom concern cis and trans conformers.

2 3

2

1

4

A O

N N

C

5

6

X2 4

B 6

α

3

1

1

4

X1

Compound

α

2

H

H

3

5

O

5

6 C-1′′

C-2′′

C-3′′

C-4′′

C-5′′

C-A

C-B

C-C

1

169.12 164.44

143.86

66.59 64.78

139.85

131.36 131.22

127.25 127.12

133.24 132.94

129.94

2

169.19 164.41

146.25 142.22

66.48 64.78

136.35

127.85

130.46

133.66

136.20

3

169.06 164.31 169.06

134.65 134.40

133.05 132.93

143.29

66.51 64.71 66.46

130.47

128.66

129.94 128.79 133.78

164.31

139.28

64.69

5

169.05 164.36

145.33 141.40

66.42 64.71

135.85 135.66

6

169.17 164.47

145.28 141.29

66.44 64.47

7

169.16 164.49

143.90

8

169.17 164.39

9

169.06 164.32

4

X

2

4

α α

129.60

130.79

133.05 132.93 148.23

133.49

130.57

124.49

148.00

133.19 132.75

130.30 130.19

127.50

148.04

121.13 120.91

140.22 140.08

130.32

123.90 123.83

147.74 147.56

123.90 123.83

66.54 64.80

133.29

131.51

128.92

139.89

128.78

146.25 142.23

66.46 64.78

136.20

130.67

130.76

133.66

136.37

146.60

66.47 64.76

134.66 134.42

131.51 131.42

128.80 128.91

142.62

128.80 128.91

CH3

H 4

1

N N

O

CH3

1 5

131.60

129.94 128.79 124.68

146.65

2 3 3

C-6′′

6

5

O

6 19 X = Cl 20 X = NO2

F 2: e structures of compounds 19 and 20.

as N-acyl substituted hydrazones of pyridinecarboxaldehydes are present in dimethyl-d6 sulfoxide solution in the form of geometric (E)-isomers about C=N double bond [27]. (E)con�guration in the stilbene part of the molecules of 1–18 was determined on the basis of their UV/Vis and IR spectra. It has been pointed out that in the UV/Vis spectra of 1–18𝜆𝜆max are in the range 290.0–385.5 nm (Table 2). According to the literature [28–30] (E)-stilbenes exhibited the values of 𝜆𝜆max in the range 290–360 nm and for (Z)-stilbenes values of 𝜆𝜆max fall in the range 260–280 nm. e infrared spectra of 1–18 show a strong band in the range of 952–970 cm−1 which according to the literature [30, 31] can be attributed to the C–H out of

142.57

130.32 131.43 129.61 131.51 131.43

the plane deformation vibration of the C–H bond of the (E)ethylene bridge of the stilbene skeleton (Table 2). e ratio of amide cis/trans conformers can be easily �uanti�ed by NMR techni�ues. In order to re�uire information about the stereochemical behavior of 1–18 in polar dimethyl-d6 sulfoxide solution, we have investigated 1 H NMR spectra of these compounds. We wish to establish whether it is possible to determine from this spectral analysis the ratio of cis/trans amide conformers of 1–18. According to our previous data [21] 1 H NMR spectrum in DMSOd6 solution of N-(E)-stilbenyl-4-oxymethylenecarbonyl substituted hydrazone of acetone is simpler [21] as it lacks the possibility of E/Z geometrical isomers about the C=N double bond. In this spectrum two sets of singlets of methylene and imine protons are seen, associated with the protons of the cis and trans amide conformers of this compound. e rate of cis/trans isomerization of this compound in DMSO-d6 has been followed by 1 H NMR at several temperatures in order to evaluate the energy barrier of cis → trans conversion. e coalescence of methylene group signals of conformers of this hydrazone of acetone in DMSO-d6 solution occurred at about 100○ C. e ΔG number values of 18.33 and 18.06 kcal/mol were found by dynamic NMR, using the coalescence temperature method [32]. e

6

Journal of Spectroscopy T 6: 1 H NMR data of compounds 10–18 (𝛿𝛿, ppm). –OCH2 – s, cis s, trans 5.17 4.73 5.24 4.75 5.23 4.75 5.21 4.74 5.23 4.73 5.23 4.75 5.20 4.76 5.26 4.76 5.26 4.77

Compound 10 11 12 13 14 15 16 17 18

–NH– s, cis s, trans 11.97 11.89

N=CH s, cis s, trans 8.07 8.14 8.15 8.53 8.31 8.45 8.34 8.72 8.20 8.32 8.41 8.76 8.39 8.75 8.48 8.53 8.32 8.44

11.88 11.93 11.71 11.70 11.75 11.69 11.92 11.84 11.99 11.92 11.87 — 11.94

Ar∗ m 8.14–6.95 8.27–6.95 8.27–6.96 8.23–6.98 8.23–6.82 8.23–6.90 8.23–6.61 8.28–6.91 8.29–7.00

∗

X2 and X1 X1 = H, Cl, NO2

X2 = Cl, NO2

O

X O R

N

N R

H

H

N H

N

H trans, E

trans, Z

X

R X O

R

N

N

H

H O

N H

N H X

cis, E

cis, Z

F 3: e structures of Z/E geometrical isomers and cis/trans amide conformers of N-substituted hydrazones of o-(m- and p-) benzaldehydes 1–18. R = (E)-stilbenyl-4-oxyalkyl-[(E)-4′ -chlorostilbenyl-4-oxyalkyl-, (E)-4′ -nitrostolbenyl-4-oxyalkyl].

Journal of Spectroscopy

7

T 7: 13 C NMR data of compounds 10–18—Part A (stilbene carbons); two values given for each carbon atom concern cis and trans conformers.

2 3 X1

1

4

α

143.89

127.62

124.47

14

144,48 142.25

126.15 126.50

124.44 124.05

15

144.49

126.98

124.47

145.78

16

144.49 144.41

126.92

124.70

17

144.49

126.92

124.39

18

144.29

127.76

126.75

12

O

1

4

N N

C

3 X 2

B 5

O

5

6

13

11

A

6 6 C-4 139.05 136.16 136.17 136.10 131.32 131.23 144.51 144.42 145.78 144.57

10

C-1 133.55 133.27 133.18 132.74 136.18 136.11

α 1

4 5

Compound

2

2

H

H

3

C-2,6

C-3,5

128.71

128.57

128.73 128.59

128.45

128.59

128.47

145.85 145.79 145.51 145.55 145.60 145.29

C-𝛼𝛼 131.21 130.29 127.93 127.76 131.43 131.67

C-𝛼𝛼′ 125.06 124.75 125.06 124.72 125.08 124.75

C-1′

C-2′ ,6′

129.54

130.06

127.66

130.09 129.91 129.73 129.83 129.73 130.02 129.69 128.60 128.23

129.57

130.05

129.15

125.83 125.35

134.45

124.05

130.03

124.05 123.68

128.64 128.55 128.61 128.52 128.87 128.79 128.54 128.04

124.04

128.53

129.71

124.30 123.97

127.93

128.45 128.36

132.99 132.85 132.82 132.66

intensities of signals of methylene and imine protons have allowed us to make measurements of the ratio of cis/trans amide conformers. It ought to be pointed out that the ratio of the conformers at 25○ C was the same as that measured at the same temperature at the end of the experiment dealing with the coalescence temperature. is is the proof that in DMSO-d6 solution of N-(E)-stilbenyloxymethylenecarbonyl substituted hydrazone of acetone the conversion of cis/trans amide conformers has been the only process of isomerization. ese investigations have been extended to N-(E)-4′ -chlorostilbenyl-4-oxymethylenecarbonyl and N-(E)-4′ -nitrostilbenyl-4-oxymethylenecarbonyl substituted hydrazones of acetone. Reaction of acetone with hydrazide of (E)-4′ -chlorostilbenyl-4-oxyacetic acid as well as (E)-4′ nitrostilbenyl-4-oxyacetic acid provided new N-substituted hydrazones of acetone 19 and 20, respectively (Figure 2). ese compounds were included in this paper for comparative purposes. e structures of 19 and 20 were determined by examining their IR and 1 H NMR spectra as well as elemental analyses (Tables 10–12). e spectral analysis revealed (E)-con�guration of the geometric isomers 19 and 20 in the stilbene part of the molecules. e infrared spectra of 19 and 20 show a strong absorption band at 962 and 961 cm−1 , respectively, which can be attributed to C–H out of plane deformation vibration of the ethylene bridge (Table 11).

124.66

C-3′ ,5′ 114.84 114.63 114.85 114.67 114.85 114.69 115.13 114.95 115.08 114.94 115.08 114.93 115.09 114.91 115.09 114.94 114.95 114.81

C-4′ 157.80 157.33 157.86 157.34 157.83 157.31 158.78 158.22 158.80 158.23 158.96 158.24 158.72 158.23 158.78 158.23 158.52 157.98

In the 1 H NMR spectra of 19 and 20 also two sets of protons of methylene and imine groups are seen. According to the literature [27] the up�eld lines of methylene protons have been assigned to amide conformers cis and down�eld lines of protons of the same groups to amide conformers trans. e intensities of 1 H NMR signals of methylene protons have allowed us to make measurements of the ratio of cis/trans amide conformers. e chemical shis and percentage of the conformers in dimethyl-d6 sulfoxide solution of 19 and 20 are summarized in Table 13. Having established the ratio of cis/trans amide conformers of 19 and 20 in DMSOd6 solutions, we have applied the similar methodology in establishing the ratio of the respective conformers of 1–18 in the same solvent. e rate of cis/trans isomerization of 10, 12 and 13 in dimethyl-d6 sulfoxide has been followed by 1 H NMR measurements at several temperatures (20, 50, 60, 70, 80, 90, 100, 110, and 120○ C) in order to evaluate the energy barrier of cis/trans conversion (Figure 3). e coalescence of methylene group signal of 10 conformers present in dimethyl-d6 sulfoxide solution occurred at about 85○ C, whereas the coalescence of methylene group of 12 and 13 conformers at about 80○ C and 100○ C, respectively. e ΔG number values of 21.85 and 21.30 kcal/mol (10), 21.48 and 21.04 kcal/mol (12) as well as 22.70 and 22.31 kcal/mol (13) were found by dynamic NMR, using the well known coalescence-temperature method [32].

8

Journal of Spectroscopy T 8: 13 C NMR data of compounds 10–18—Part B, two values given for each carbon atom concern cis and trans conformers.

2 3 X1

α

1

4

A O

1 N

C

α

4

B 6

6

3 X 2

N

1

4 5

Compound

2

2

H

H

3

5

O

5

6 C-1′′

C-2′′

C-3′′

C-4′′

C-5′′

C-6′′

C-A

C-B

C-C

10

169.96 164.34

147.79 143.05

66.40 64.64

130.56

127.88 127.81

130.37

127.63

124.47 124.28

128.43

11

169.02 164.34

145.33 141.41

66.41 64.72

130.19

135.79 135.66

131.31 131.22

127.74 127.69

148.03 147.99

124.21 124.02

169.15 164.45 169.08 164.99

145.28 141.29 145.86 145.80

66.43 64.72 66.49 64.81

140.22 140.08

129.58 129.42

123.91 123.84

123.91 123.84

128.74

139.90

131.23

127.09

147.74 147.57 133.29 133.02

126.93

131.36

169.11 164.32 168.96 164.21

146.24 145.84

66.43 64.80 66.45 64.76

136.34 136.20

126.40 126.11 133.02 132.93

130.76 130.67 129.18 129.10

137.66 133.08

133.00 132.84 129.18 129.10

129.09 129.52 133.02 132.93

130.81 130.59

129.71 129.62 135.97 135.85

132.99 132.84 130.47 130.38

133.79 133.50

124.50 124.17

129.20

148.26

148.25 148.00 121.29 121.08

129.56

123.87 123.83

147.74 147.57

123.87 123.83

12 13 14 15 16 17 18

146.64

169.18 164.54 169.19 164.50

143.32 139.33 144.40 141.64

66.41 64.73 66.43 64.80

169.07 164.36

144.20 141.32

66.39 64.75

133.66

133.20 140.20 140.07

e intensities of the 1 H signals of the protons of methylene groups of 1–18 have allowed us to make measurements of the ratio of cis/trans conformers. e chemical shis and percentage of conformers of 1–18 in DMSO-d6 solution are summarized in Table 9. It ought to be pointed out that the ratio of the conformers at 20○ C is the same at the beginning and at the end of the experiment dealing with the coalescence temperature. is can serve as a proof that in the DMSO-d6 solution of the investigated compounds 1–18 the conversion of cis/trans amide conformers is the only process of isomerization. We have also investigated the 13 C NMR spectra of N-(E)-stilbenylo-4-oxymethylene carbonyl substituted hydrazones of acetone 19 and 20. e 13 C NMR data of 19 and 20 are given in the Table 12. Assignments of 13 C NMR resonances of these compounds were deduced on the basis of the literature data as well as the signal multiplicities, chemical shi theory and additivity rules. In the 13 C NMR spectra of these compounds two sets of carbon signals are seen. According to the 13 C assignments for N-acyl- and N-aroylhydrazones of methyl pyruvate [27] as well as the hydrazones of aromatic aldehydes [33], the up�eld lines of carbonyl carbons and the down�eld lines of methylene carbons have been assigned to amide conformer trans whereas the down�eld lines of carbonyl carbons and the up�eld lines of methylene carbons to the conformer cis.

142.60

129.07

Having established the ratio of cis/trans amide conformers of 19 and 20 in DMSO-d6 solutions by 1 H NMR technique, we have applied the similar methodology in establishing the ratio of conformers of N-substituted hydrazones of acetone on the basis of the height of the signals of the carbons of methylene groups in the 13 C NMR spectra. e chemical shis and the percentage of cis/trans amide conformers of 19 and 20 calculated from the heights of the signals of the protons in the 1 H NMR spectra and the carbons in the 13 C NMR spectra are given in the Table 13. It ought to be pointed out that in the cases of these compounds the differences between the values calculated from the data obtained from the 1 H NMR spectra and 13 C NMR spectra are at the level 12%. Having established on the basis of 13 C NMR data the ratio of cis/trans amide conformers of N-substituted hydrazones of acetone 19 and 20, in DMSO-d6 solution, we have applied the similar methodology in establishing the ratio of conformers of compounds 1–18 in the same solution. In the 13 C NMR spectra of 1–18 two sets of signals of carbon (Tables 4, 5, 7, and 8) are seen. Assignments of 13 C NMR resonances of these compounds were deduced on the literature data, as well as signal multiplicities, chemical shi theory and additivity rules. It ought to be pointed out that up�eld lines of carbonyl carbons and the down�eld lines of methylene carbons have been assigned to amide conformer trans, whereas down�eld

Journal of Spectroscopy

9

T 9: 1 H and 13 C NMR data of cis/trans conformers of 1–18 in DMSO-d6 . 1

Compound 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

H NMR O–CH2 – s(𝛿𝛿, ppm) [height] 5.20 [127.8] 4.27 [81.5] 5.20 [116.1] 4.72 [72.5] 5.18 [56.8] 4.71 [36.1] 5.17 [122.1] 4.73 [65.7] 5.23 [122.0] 4.75 [88.4] 5.23 [117.2] 4.75 [66.8] 5.20 [70.7] 4.72 [44.4] 5.20 [77.8] 4.71 [45.8] 5.18 [112.6] 4.71 [71.0] 5.17 [143.7] 4.73 [72.3] 5.24 [162.4] 4.75 [111.4] 5.23 [68.5] 4.75 [38.6] 5.21 [113.6] 4.74 [66.6] 5.23 [49.1] 4.73 [26.8] 5.23 [82.7] 4.75 [48.3] 5.20 [125.8] 4.76 [63.8] 5.26 [43.5] 4.76 [29.1] 5.26 [106.8] 4.77 [56.51]

13

Conformer Cis % Trans % 61.06 38.93 61.55 38.44 61.14 38.55 65.01 34.98 57.98 42.01 63.69 36.31 61.43 38.57 62.94 37.06 61.33 38.68 66.52 33.48 59.31 40.68 63.95 36.04 63.04 36.95 64.69 35.30 63.12 36.87 66.35 33.64 59.91 40.08 65.39 34.60

C NMR O–CH2 – s(𝛿𝛿, ppm) [height] 64.78 [47.50] 66.59 [30.90] 64.78 [16.8] 66.48 [11.4] 64.74 [18.20] 66.51 [11.00] 64.69 [42.50] 66.46 [23.20] 64.71 [24.40] 66.42 [24.40] 64.71 [21.60] 66.44 [15.30] 64.80 [13.60] 66.54 [9.10] 64.78 [12.90] 66.46 [8.30] 64.76 [8.20] 66.47 [5.50] 64.64 [32.70] 66.40 [15.60] 64.71 [55.30] 66.40 [37.5] 64.71 [35.90] 66.42 [18.10] 64.81 [25.70] 66.49 [12.51] 64.80 [28.5] 66.49 [16.5] 64.76 [24.60] 66.45 [14.90] 64.72 [25.30] 66.40 [13.20] 64.80 [16.80] 66.43 [11.90] 67.74 [39.30] 66.39 [20.50]

Conformer Cis % Trans % 60.58 39.41 59.57 40.42 62.32 37.67 64.68 35.31 58.50 41.49 58.53 41.46 59.91 40.08 60.84 39.15 59.85 40.14 67.70 32.29 59.59 40.40 66.48 33.51 67.26 32.74 63.33 36.66 62.27 37.72 65.71 34.28 58.53 41.46 65.71 34.28

Δ%

0.48 1.98 1.18 0.33 0.52 5.16 1.51 2.10 1.47 1.18 0.28 2.53 4.21 1.36 0.85 0.64 1.38 0.32

e difference between the percentage of the conformers of compounds 1–18 calculated from 1 H NMR and 13 C NMR data.

T 10: Chemical and physical data of compounds 19-20. Compound 19 20

Formula Mol. weight C19 H19 N2 O2 Cl 343.15 C19 H19 N3 O4 353.15

Elemental analyses Calculated (found) C H N

Yield [%]

M.p. [○ C] 144–6

𝑅𝑅𝑓𝑓 (TLC) 0.69

66.66 (66.70)

5.55 (5.51)

8.18 (8.03)

41

186–8

0.89

64.55 (64.40)

5.37 (5.28)

11.89 (11.87)

45

10

Journal of Spectroscopy T 11: IR (KBr) and 1 H NMR data of compounds 19 and 20.

19

IR (cm−1 ) 𝛿𝛿–CH=CH– trans E

20

961

Compound

1

–OCH2 – 5.00 4.66 5.02 4.69

962

H NMR (𝛿𝛿, ppm)

NH 10.44 10.21 10.46 10.23

CH3 /CH3 1.94 1.97 1.88 1.95

Ar 6.86–8.32 6.90–8.23

T 12: 13 C NMR data of compounds 19 and 20. (a)

2 3



3

α 1

2

4

1

4 X

α 5

H



6

O A

B N N C

CH3 E

O

5

D CH3

6 19 X = Cl 20 X = NO2

Compound 19 20

C-1 144.30 144.24

C-2,6 128.40 128.34

C-3,5 126.73 124.14

Carbon C-4 145.62 145.58

C-𝛼𝛼 132.84 132.72

137.19

126.06

128.54

127.08

126.32

C-𝛼𝛼′ 123.88 123.18 127.87 127.78

(b)

Compound 19 20

C-1′ 129.06 128.87 129.68 130.11

C-2′ ,6′ 129.56 129.28 127.55 127.62

C-3′ ,5′ 114.79 114.65 114.55 114.72

C-4′ 158.60 158.21 157.42 157.79

lines of carbonyl carbons and the up�eld lines of methylene carbons to amide conformer cis. e chemical shis and the percentage of the cis/trans amide conformers of compounds 1–18 calculated from the heights of the signals of the protons in the 1 H NMR spectra and the carbons in the 13 C NMR spectra are given in the Table 10. It ought to be pointed out that in the cases of compounds 1, 4, 5, 11, 14, 15, 16, and 18 the differences between the values of the percents calculated from the data obtained form the 1 H and 13 C NMR spectra are at the level below 1%. In the cases of compounds 2, 3, 7, 9, 10 and 17 these differences are at the level of 1-2%, whereas in the cases of 8 and 12 at the level of 2-3%. Only in the cases of compounds 6 and 13 these differences have the values 5.16% and 4.21%, respectively.

3. Conclusions It follows from the obtained results that the E-geometrical isomers of 1–18 as well as 19-20 undergo a rapid cis/trans

Carbon C-A 64.83 65.94 64.87 66.03

C-B 168.57 163.24 168.72 163.43

C-C 151.23 151.30

C-D 25.21 24.99 25.24 25.02

C-E 17.62 17.08 17.09 17.63

amide equilibrium when dissolved in DMSO-d6 solution, with the cis amide conformer predominating. e ratio of amide cis/trans conformers of 1–18 and 19-20 can be determined on the basis of the analysis of both 1 H and 13 C NMR spectra. To the best of our knowledge no work has been published on the using of 13 C NMR spectra in establishing the ratio of amide cis/trans conformers of N-substituted hydrazones.

4. Experimental e NMR measurements were performed on a Varian Mercury Spectrometer operating at 300.07 MHz (proton) and 75.46 MHz (carbon). Data were obtained from DMSO-d6 solutions at concentrations between 0.25 and 0.40 M at ambient temperature. e chemical shis were referenced to tetramethylsilane. 1 H NMR spectra were recorded at a proton frequency of 300.07 MHz with a spectral width of 9000 Hz. e acquisition time was 2 s and a relaxation delay 1 s; 64

Journal of Spectroscopy

11

T 13: 1 H and 13 C NMR data of cis/trans conformers of N-(E)-4-X-stilbenyl-4′ -oxymethylenecarbonyl substituted hydrazones of acetone (19, 20); 19 X = Cl. 20 X = NO2 . 1

Compound 19 20 ∗

H NMR –OCH2 – s(𝛿𝛿, ppm) [height] 5.00 [62.0] 4.66 [45.3] 5.02 [60.5] 4.69 [40.33]

Conformer cis % trans % 57.78 42.22 59.66 40.33

13

C NMR –OCH2 – s(𝛿𝛿, ppm) [height] 64.86 [25.5] 66.00 [17.0] 64.03 [37.2] 65.94 [26.4]

Conformer cis % trans % 60.00 40.00 58.49 41.50

∗

Δ%

2.22 1.17

e difference between the percentage of the conformers calculated from the 1 H NMR and 13 C NMR data.

scans with 44.922 data points each were used. e 13 C NMR spectra were obtained using a spectral width of 23,000 Hz and 1.5 s acquisition time; 2476 scans with 68992 data points each were used. UV/Vis spectra were recorded with a SPECORD UV/Vis spectrophotometer in CH3 OH (1–3, 7–9, 13–15) and DMSO (4–6, 10–12, 16–18). IR spectra were recorded with a FTIR Bruker IFS-113 V spectrophotometer in KBr pellets. Elemental analyses were performed with a Vector Euro EA 3000 analyzer. 𝑅𝑅𝑓𝑓 values to silica gel F254 plates (Merck) were developed with chloroform-methanol 50 : 1 and observed under UV light (𝜆𝜆 = 254 and 366 nm). Hydrazides of (E)-stilbenyloxyacetic acid, (E)4′ -chlorostilbenyl-4-oxyacetic acid [34] and (E)-4′ nitrostilbenyl-4-oxyacetic acid [35], as well as N-(E)-4stilbenyloxymethylene- carbonyl substituted hydrazone of acetone [21] were obtained according to the literature. e Synthesis of N-(E)-4 ′ -chloro-(nitro)stilbenyl-4-oxymethylenecarbonyl-Substituted Hydrazone of Acetone 19-20. General procedure. A solution of (E)-4′ -chloro- (nitro-)-4-oxyacetic acid hydrazide (1 × 10−3 mol) in 60 mL of acetone was re�uxed for 3 hours. en half of the volume of acetone was evaporated on a rotatory evaporator and the residue was cooled in the refrigerator for 3 hours. e formed crystals were �ltered, dried, and recrystallized form acetone (Table 10). e Synthesis of N-(E)-stilbenyl-4-oxymethylenecarbonylSubstituted Hydrazones of ortho-(meta- and para-) chloro(nitro-)benzaldehydes 1–18. General Procedure. To a solution of 1 mmole of the corresponding hydrazide of (E)stilbenyloxyacetic acid in 20 mL of DMF, 1.5 mmole of the corresponding o-(m- and p-) chloro- (nitro-) benzaldehyde was added. e reaction mixture was re�uxed for 2 hours. en the solvent was evaporates to dryness. e obtained solid was dissolved in 50 mL of boiling absolute ethanol, then boiled for 1 hour and concentrated to ca. 1/2 volume on a rotatory evaporator. e residue was cooled, the precipitated solid was �ltered off, dried, and recrystallized form corresponding solvent (Table 1).

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Hindawi Publishing Corporation http://www.hindawi.com

Bioinorganic Chemistry and Applications Hindawi Publishing Corporation http://www.hindawi.com

Volume 2014

International Journal of

Chemistry Volume 2014

Volume 2014

Spectroscopy Volume 2014

Hindawi Publishing Corporation http://www.hindawi.com

Volume 2014