Organic Chemistry International

Volume 2014 (2014), Article ID 576715, 9 pages

http://dx.doi.org/10.1155/2014/576715

Research Article

Synthesis of Novel Symmetrical and Unsymmetrical o-Phthalic Acid Diamides

Padam Praveen Kumar, Yervala Dathu Reddy, Chittireddy Venkata Ramana Reddy, Bhoomireddy Rama Devi, and Pramod Kumar Dubey

Department of Chemistry, Jawaharlal Nehru Technological University Hyderabad College of Engineering, Kukatpally, Hyderabad, Andhra Pradesh 500085, India

Received 23 January 2014; Revised 26 March 2014; Accepted 27 March 2014; Published 5 May 2014

Academic Editor: Joseph E. Saavedra

Copyright © 2014 Padam Praveen Kumar et al. This 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.

Abstract.

Phthalic anhydride was treated with secondary amines in acetic acid yielding 2-(diethyl (or) 4-alkylpiperazine or morpholine-1-carbonyl) benzoic acids. The latter were reacted, again, with secondary amines and arylamines by using the coupling reagent HATU and Et₃N as a base in DMF giving the novel symmetrical o-phthalic acid diamides , unsymmetrical o-phthalic acid diamides , and primary amidic-secondary amidic containing unsymmetrical o-phthalic acid diamides , respectively.

1. Introduction

Phthalic anhydride is used in the manufacture of dialkylphthalates [1, 2] which find application as plasticisers for polymers like polyvinyl chloride (PVC) and polyvinylacetate (PVA). It is used in the manufacture of phenolphthalein indicator [3, 4], anthraquinone [5] (a versatile, raw materials in the dye industry [6]), and metal phthalocyanines [7]. Phthalocyanine compounds are used in a variety of applications [7] in addition to their use as pigments, in paints [8] and in many types of dyestuffs [7]. Phthalic anhydride derivatives have been widely reported to possess beneficial pharmaceutical effects, like analgesic [9], anti-inflammatory [10] and antiviral effects [11].

Dunlap and Cummer reported [12] the preparation of symmetrical o-phthalic acid diamides [o-ArNHCOC₆H₄CONHAr] by the reaction of phthaloyl dichloride with two moles of aniline in ether at RT. Dann et al. reported [13] the preparation of symmetrical o-phthalic acid diamides by the reaction of phthaloyl dichloride with two moles of aniline in the presence of sodium fluoride in benzene under reflux for 1 h. de Toranzo and Brieux reported [14] the synthesis of unsymmetrical diamides [ArNHCOC₆H₄CONHAr¹] by the reaction of phthalphenylisoimide with anilines in ether at RT. Reynolds reported [15] that unsymmetrical diamides [ArNHCOC₆H₄CONHAr¹] can be made by the reaction of N-arylphthalamic acid with the sodium salt of o- or p-methylaniline in an atmosphere of nitrogen for 1 h at 75°C. However, these methods suffer from drawbacks such as long reaction times, excess use of organic solvents, harsh refluxing conditions, and preparation of difficult starting materials from phthalic anhydride by the reaction with primary amines in the presence of trifluoroacetic anhydride. Keeping these facts in mind, we wish to report our results on reactions of phthalic anhydride with primary and secondary amines using HATU as a coupling reagent. Probably, this appears to be the first ever case of facile preparation of symmetrical and unsymmetrical o-phthalic acid diamides. The use of HATU as a coupling agent has been reported in the literature for reactions such as amide bond formation in solid phase synthesis [16–18] and peptides synthesis [19]. However, its use in the preparation of diamides from phthalic anhydride with amines has probably not been reported so far.

2. Results and Discussion

Phthalic anhydride 1 was treated with the secondary amines 2a –2e in acetic acid at RT for 10–15 min resulting in the formation of 2-(diethyl (or) 4-alkylpiperazine (or) morpholine-1-carbonyl)benzoic acid 3a –3e. Reaction of 3a with the piperazine 2b in the presence of o-(7-azabenzotriazol-1-yl)-1,1,3,3-tetramethyluroniumhexafluorophosphate (HATU) and Et₃N at 0–5°C for 40–45 min in DMF gave 5a. Alternatively, this compound was prepared by treating 2-(piperazine-1-carbonyl)benzoic acid 3b withdiethylamine 2a by HATU and Et₃N at 0–5°C for 40–45 min in DMF to form N,N-diethyl-2-(piperazine-1-carbonyl)benzamide 5a. This reaction was examined by carrying out the condensation of 2-(diethylcarbonyl)benzoic acid 3a (1 mmol) with piperazine 2b (1 mmol) in the presence different coupling reagents (HATU, EDC.HCl/HOBt (1-hydroxybenzotriazole), DCC (N,N′-dicyclohexylcarbodiimide), HBTU and PTSA (4-methylbenzenesulfonic acid)) and tertiary bases (Et₃N and DBU (2, 3, 4, 6, 7, 8, 9, 10-octahydropyrimido azepine) at different temperatures in DMF as a solvent (Table 1) with a view to study the generalisation of condensation between 3 and 2. However, coupling of 3a with 2b in the presence of HATU and Et₃N at 0–5°C for 40–45 min in DMF was found to be the best method giving 5a in quality and yield (≥80%) (Table 1, entry 1).

Table 1: Effect of coupling reagent, tertiary base, and temperature on condensation of 3a with 2b in DMF yielding 5a.

Entry
Coupling reagent
Tertiary base
Temp./°C
Time/min
5a (%)

1
HATU

0–5
40–45
80

2
HATU
Et₃N
RT
40–45
78

3
HATU
DBU
0–5
55–65
70

4
HATU
DBU
RT
50–55
70

5
HATU
Et₃N
50–60
35–40
73

6
DCC
—
0–5
120–130
45

7
DCC
—
RT
100–110
48

8
DCC/HOBt
—
0–5
110–120
50

9
DCC/HOBt
—
RT
100–110
50

10
DCC/HOBt
—
50–60
55–60
72

11
EDC·HCl/HOBt
Et₃N
0–5
80–85
70

12
EDC·HCl/HOBt
Et₃N
RT
70–80
70

13
EDC·HCl/HOBt
DBU
0–5
70–80
60

14
EDC·HCl/HOBt
DBU
RT
70–75
65

15
EDC·HCl/HOBt
Et₃N
50–60
65–70
72

16
HBTU
Et₃N
0–5
70–75
70

17
HBTU
Et₃N
RT
65–70
70

18
HBTU
DBU
0–5
70–80
65

19
HBTU
DBU
RT
65–75
65

20
HBTU
Et₃N
50–60
50–55
70

21
PTSA
—
0–5
120–125
—

22
PTSA
—
RT
120–125
—

23
PPA
—
100
60–65
40

Using the above-stated optimised conditions, 3a –3e were condensed into 2a –2e using HATU and Et₃N at 0–5°C for 40–65 min in DMF yielding 4a –4e and 5a –5j (Scheme 1) (Tables 2 and 3) in excellent yield. The structures of the products have been established on the basis of their spectral and analytical data. (Please see experimental section)

Table 2: Characterization data, reaction time, and yields of 3a–3e obtained 1 and 2a–2e.

Entry
Starting material used
Product obtained
Time (min)
Yield≠
M.P (°C)

1
2a
3a
10–12
85
145–148

2
2b
3b
12–15
85
>220

3
2c
3c
15–18
83
>220

4
2d
3d
15–18
80
>220

5
2e
3e
15–20
81
>220

Refers to yields of crude products only.

Table 3: Characterization data, reaction time, and yields of 4a–4e and 5a–5j obtained from 3a–3e and 2a–2e.

Entry
Starting material used
Product obtained
Time (min)
Yield≠
M.P (°C)

1
3a
2a
4a
40–45
85
>220

2
3b
2b
4b
40–45
85
>220

3
3c
2c
4c
50–55
80
>220

4
3d
2d
4d
50–55
80
>220

5
3e
2e
4e
40–45
80
>220

6
3a
2b
5a
40–45
85
>220

7
3a
2c
5b
50–55
81
110–112

8
3a
2d
5c
50–55
84
115–118

9
3a
2e
5d
50–55
85
80–82

10
3b
2a
5a
40–45
83
>220

11
3b
2c
5e
50–55
84
>220

12
3b
2d
5f
50–55
85
>220

13
3b
2e
5g
60–65
85
85–87

14
3c
2a
5b
60–65
81
110–112

15
3c
2b
5e
50–55
83
>220

16
3c
2d
5h
50–55
85
>220

17
3c
2e
5i
50–55
85
90–92

18
3d
2a
5c
60–65
80
115–118

19
3d
2b
5f
50–55
80
>220

20
3d
2c
5h
40–45
85
>220

21
3d
2e
5j
40–45
83
>220

22
3e
2a
5d
40–45
80
80–82

23
3e
2b
5g
50–55
84
85–87

24
3e
2c
5i
50–55
84
90–92

25
3e
2d
5j
40–45
83
>220

Refers to yields of crude products only.

Scheme 1: Synthetic routes to 4a –4e and 5a –5j.

Condensation of 3a –3e with arylamines 6a –6e in the presence of HATU and Et₃N at 0–5°C for 40–55 min in DMF gave primary amidic-secondary amidic containing unsymmetrical o-phthalic acid diamides [o-R₁R₁NCOC₆H₄CONHAr] 7a –7y (Scheme 2) (Table 4). The structures of the products have been established on the basis of their spectral and analytical data. An alternate protocol was attemptedto synthesize 7a –7y by treatment of 1 with aniline 6a in acetic acid at 0–5°C for 10–15 min which gave 2-(phenylcarbamoyl)benzoic acid 8a ¹⁸ and subsequent reaction of 8a with diethylamine 2a in the presence of HATU and Et₃N at RT for 20–25 min in DMF which resulted in the formation of 2-phenylisoindoline-1, 3-dione 9a ¹⁸.

Table 4: Characterization data reaction time and yield of 7a–7y obtained from 3a–3e and 6a–6e.

Entry
Starting material used
Product obtained
Time (min)
Yield≠
M.P (°C)

1
3a
6a
7a
40–45
85
115–118

2
3b
6a
7b
50–55
82
120–123

3
3c
6a
7c
40–45
84
123–125

4
3d
6a
7d
50–55
85
>220

5
3e
6a
7e
50–55
80
126–128

6
3a
6b
7f
40–45
83
128–130

7
3b
6b
7g
40–45
82
138–140

8
3c
6b
7h
50–55
82
120–123

9
3d
6b
7i
50–55
85
>220

10
3e
6b
7j
40–45
80
122–124

11
3a
6c
7k
50–55
82
120–124

12
3b
6c
7l
40–45
85
130–132

13
3c
6c
7m
50–55
85
170–174

14
3d
6c
7n
50–55
80
>220

15
3e
6c
7o
40–45
80
140–143

16
3a
6d
7p
40–45
80
125–128

17
3b
6d
7q
50–55
82
135–137

18
3c
6d
7r
50–55
82
180–183

19
3d
6d
7s
40–45
80
>220

20
3e
6d
7t
40–45
85
142–145

21
3a
6e
7u
40–45
84
128–130

22
3b
6e
7v
40–45
85
133–135

23
3c
6e
7w
50–55
80
190–192

24
3d
6e
7x
50–55
82
>220

25
3e
6e
7y
40–45
84
145–148

Refers to yields of crude products only.

Scheme 2: Synthetic routes to 7a –7y.

3. Conclusion

In conclusion, we have developed novel syntheses of symmetrical 4a –4e and unsymmetrical 5a –5j and 7a –7y o-phthalic acid diamides. This approach presents a simple and useful synthetic process which requires a few minutes of reaction time, easily available starting materials and straight forward and easy workup procedure. Probably, this appears to be the first ever case of facile preparation of symmetrical and unsymmetrical o-phthalic acid diamides. The use of HATU as a coupling agent has been reported in the literature for reactions such as amide bond formation in solid phase synthesis and peptides synthesis. However, its use in the preparation of diamides from phthalic anhydride with amines has probably not been reported so far. The overall yields of these compounds are very good.

4. Materials and Methods

Melting points are uncorrected and were determined in open capillary tubes in sulphuric acid bath, TLC was run on silica gel-G, visualization was done using iodine or UV light, and IR spectra were recorded using PerkinElmer 1000 instrument in KBr pellets. 1HNMR spectra were recorded in DMSO-d₆ using TMS as internal standard using 400 MHz spectrometer. Mass spectra were recorded on Agilent-LCMS instrument under CI conditions and given by values only. Starting 1, 2, and 6 were obtained from commercial sources and used as such.

4.1. Preparation of 3a –3e

A mixture of 1a (10 mM), 2a –2e (10 Mm) and CH₃COOH (20 mL) was stirred at RT for 10–20 min. A colourless solid separated out from reaction mixture which was filtered, washed with hexane (10 mL), and dried. The crude product was recrystallized from suitable solvent to obtain 3a –3e.

4.2. Preparation of 4a –4e & 5a –5j

A mixture of 3a –3e (10 mM), 2a –2e (10 mM) HATU (10 mM), Et₃N (10 mM), and DMF (15 mL) was stirred at 0–5°C for 40–65 min. Then, ice-cold water (50 mL) was added to the reaction mixture. The separated solid was filtered, washed with water (10 mL), and dried. The product was recrystallized from a suitable solvent to obtain 4a –4e and 5a –5j.

4.3. Preparation of 7a –7y

A mixture of 3a –3e (10 mM), 6a –6e (10 mM), HATU (10 mM), Et₃N (10 mM), and DMF (15 mL) was stirred at 0–5°C for 40–55 min. Then, ice-cold water (50 mL) was added to the reaction mixture. The separated solid was filtered, washed with water (10 mL), and dried. The product was recrystallized from a suitable solvent to obtain 7a –7y.

5. Supporting Information

3a: IR (KBr): 3100–3400  (broad medium, –NH and –OH groups put together), 1720  (sharp, strong, –CO– of acid group), 1655  (sharp, storng, –CO– of amide group); ¹H-NMR: 0.8 (t, 3H, –CH₃), 1.2 (t, 3H, –CH₃), 3.0 (q, 2H, –CH₂), 3.6 (q, 2H, –CH₂), 7.0–8.0 (m, 4H, Ar-H), 13.00 (s, 1H, –COOH, D2O exchangeable), 10.12 (s, 1H, –NH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 12.3, 41.4, 123.1, 128.5, 129.3, 129.5, 160.2, 165.5. Ms: = 222 (M+. + 1).

3b: IR (KBr): 3100–3400  (broad medium, –NH and –OH groups put together), 1725  (sharp, strong, –CO– of acid group), 1670  (sharp, storng, –CO– of amide group); ¹H-NMR: 2.2 (s, 1H, –NH), 3.0 (t, 2H, –CH₂), 3.2 (t, 2H, –CH₂), 3.4 (t, 2H, –CH₂), 3.8 (t, 2H, –CH₂), 7.0–8.0 (m, 4H, Ar-H), 13.00 (s, 1H, –COOH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 49.4, 50.1, 51.4, 51.9, 124.1, 125.5, 127.3, 128.5, 161.2, 164.8. Ms: = 235 (M+. + 1).

3c: IR (KBr): 3100–3400  (broad medium, –NH and –OH groups put together), 1730  (sharp, strong, –CO– of acid group), 1655  (sharp, storng, –CO– of amide group); ¹H-NMR: 1.2 (t, 3H, –CH₃), 2.6 (q, 2H, –CH₂), 3.0 (t, 2H, –CH₂), 3.2 (t, 2H, –CH₂), 3.4 (t, 2H, –CH₂), 3.8 (t, 2H, –CH₂), 7.0–8.0 (m, 4H, Ar-H), 13.2 (s, 1H, –COOH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 12.5, 49.4, 50.1, 50.9, 51.9, 52.2, 123.1, 124.5, 125.3, 127.5, 163.2, 164.8. Ms: = 263 (M+. + 1).

3d: IR (KBr): 3100–3400  (broad medium, –NH and –OH groups put together), 1720  (sharp, strong, –CO– of acid group), 1660  (sharp, storng, –CO– of amide group); ¹H-NMR: 1.6 (t, 3H, –CH₃), 3.0 (t, 2H, –CH₂), 3.2 (t, 2H, –CH₂), 3.4 (t, 2H, –CH₂), 3.8 (t, 2H, –CH₂), 7.0–8.0 (m, 4H, Ar-H), 13.1 (s, 1H, –COOH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 39.4, 55.1, 55.9, 55.9, 55.2, 126.1, 127.5, 128.3, 129.5, 160.2, 165.8. Ms: = 249 (M+. + 1).

3e: IR (KBr): 3100–3400  (broad medium, –NH and –OH groups put together), 1720  (sharp, strong, –CO– of acid group), 1655  (sharp, storng, –CO– of amide group); ¹H-NMR: 3.0 (t, 2H, –CH₂), 3.2 (t, 2H, –CH₂), 3.4 (t, 2H, –CH₂), 3.8 (t, 2H, –CH₂), 7.0–8.0 (m, 4H, Ar-H), 13.1 (s, 1H, –COOH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 50.2, 50.6, 71.9, 72.2, 125.1, 125.5, 126.3, 127.5, 162.2, 164.8. Ms: = 236 (M+. + 1).

4a: IR (KBr): 3100–3400  (broad medium, –NH–), 1680  (sharp, strong, –CO– of amide group), 1665  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.2 (t, 6H, –CH₃, –CH₃), 1.4 (t, 6H, –CH₃, –CH₃), 2.8 (q, 4H, –CH₂, –CH₂) 3.2 (q, 4H, –CH₂, –CH₂), 7.0–8.0 (m, 4H, Ar-H). ¹³C NMR (DMSO-d₆, 400 MHz): 12.9, 14.1, 31.6, 36.7, 39.1, 43.5, 125.3, 126.5, 127.1, 129.3, 163.6, 169.6. Ms: = 277 (M+. + 1).

4b: IR (KBr): 3100–3400  (broad medium, –NH–), 1685  (sharp, strong, –CO– of amide group), 1665  (sharp, strong, –CO– of amide group); ¹H-NMR: 2.2 (s, 2H, –NH, –NH), 3.0 (t, 8H, Four –CH₂ groups), 3.4 (t, 8H, Four –CH₂ groups), 7.0–8.0 (m, 4H, Ar-H). ¹³C NMR (DMSO-d₆, 400 MHz): 47.4, 48.6, 49.7, 50.9, 51.5, 52.4, 125.3, 125.5, 127.1, 128.6, 164.3, 167.6. Ms: = 303 (M+. + 1).

4c: IR (KBr): 3100–3400  (broad medium, –NH–), 1660  (sharp, strong, –CO– of amide group), 1665  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.3 (t, 6H, –CH₃, –CH₃), 2.8 (q, 4H, –CH₂, –CH₂), 3.2 (t, 8H, Four –CH₂ groups), 3.2 (t, 8H, Four –CH₂ groups), 7.0–8.0 (m, 4H, Ar-H). ¹³C NMR (DMSO-d₆, 400 MHz): 12.3, 16.1, 46.4, 47.6, 48.7, 49.1, 50.5, 51.4, 123.3, 124.5, 128.1, 128.9, 164.6, 168.6. Ms: = 359 (M+. + 1).

4d: IR (KBr): 3100–3400  (broad medium, –NH–), 1670  (sharp, strong, –CO– of amide group), 1665  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.4 (t, 6H, –CH₃, –CH₃), 3.0 (t, 8H, Four –CH₂ groups), 3.2 (t, 8H, Four –CH₂ groups), 7.0–8.0 (m, 4H, Ar-H). ¹³C NMR (DMSO-d₆, 400 MHz): 32.3, 33.4, 48.4, 48.9, 49.7, 50.5, 52.4, 55.3, 125.3, 125.6, 128.3, 129.9, 165.2, 169.3. Ms: = 331 (M+. + 1).

4e: IR (KBr): 3100–3400  (broad medium, –NH–), 1675  (sharp, strong, –CO– of amide group), 1665  (sharp, strong, –CO– of amide group); ¹H-NMR: 3.0 (t, 8H, Four –CH₂ groups), 3.2 (t, 8H, Four –CH₂ groups), 7.0–8.0 (m, 4H, Ar-H). ¹³C NMR (DMSO-d₆, 400 MHz): 49.3, 49.9, 50.7, 52.8, 55.9, 56.8, 125.4, 126.3, 127.4, 128.9, 164.2, 167.3. Ms: = 305 (M+. + 1).

5a: IR (KBr): 3100–3400  (broad medium, –NH–), 1690  (sharp, strong, –CO– of amide group), 1660  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.0–1.2 (t, 6H, –CH₃, –CH₃), 2.2 (s, 1H, –NH), 3.0 (t, 4H, –CH₂, –CH₂), 3.2 (t, 4H, –CH₂, –CH₂), 3.4 (q, 2H, –CH₂), 3.6 (q, 2H, –CH₂, –CH₂), 7.0–8.0 (m, 4H, Ar-H). ¹³C NMR (DMSO-d₆, 400 MHz): 12.9, 31.7, 43.5, 44.6, 51.1, 52.5, 123.1, 124.3, 128.3, 129.6, 161.7, 165.5. Ms: = 290 (M+. + 1).

5b: IR (KBr): 3100–3400  (broad medium, –NH–), 1680  (sharp, strong, –CO– of amide group), 1650  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.0–1.2 (t, 6H, –CH₃, –CH₃), 1.4 (t, 3H, –CH₃), 2.2 (q, 2H, –CH₂), 3.0 (t, 4H, –CH₂, –CH₂), 3.2 (t, 4H, –CH₂, –CH₂), 3.4 (q, 2H, –CH₂), 3.6 (q, 2H, –CH₂, –CH₂), 7.0–8.0 (m, 4H, Ar-H). ¹³C NMR (DMSO-d₆, 400 MHz): 12.9, 13.6, 31.5, 44.5, 45.6, 48.6, 54.1, 55.5, 123.6, 125.3, 128.3, 129.6, 162.7, 165.4. Ms: = 318 (M+. + 1).

5c: IR (KBr): 3100–3400  (broad medium, –NH–), 1695  (sharp, strong, –CO– of amide group), 1655  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.0–1.2 (t, 6H, –CH₃, –CH₃), 1.8 (t, 3H, –CH₃), 3.0 (t, 4H, –CH₂, –CH₂), 3.2 (t, 4H, –CH₂, –CH₂), 3.4 (q, 2H, –CH₂), 3.6 (q, 2H, –CH₂, –CH₂), 7.0–8.0 (m, 4H, Ar-H). ¹³C NMR (DMSO-d₆, 400 MHz): 13.9, 32.7, 41.5, 44.6, 45.5, 53.1, 54.5, 122.3, 125.3, 129.2, 129.9, 164.7, 166.4. Ms: = 304 (M+. + 1).

5d: IR (KBr): 3100–3400  (broad medium, –NH–), 1680  (sharp, strong, –CO– of amide group), 1655  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.0–1.2 (t, 6H, –CH₃, –CH₃), 3.0 (t, 4H, –CH₂, –CH₂), 3.2 (t, 4H, –CH₂, –CH₂), 3.4 (q, 2H, –CH₂), 3.6 (q, 2H, –CH₂, –CH₂), 7.0–8.0 (m, 4H, Ar-H). ¹³C NMR (DMSO-d₆, 400 MHz): 13.2, 33.4, 44.3, 45.2, 50.1, 52.4, 124.2, 123.5, 125.4, 125.7, 160.3, 165.6. Ms: = 291 (M+. + 1).

5e: IR (KBr): 3100–3400  (broad medium, –NH–), 1690  (sharp, strong, –CO– of amide group), 1665  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.4 (t, 3H, –CH₃), 2.2 (q, 2H, –CH₂), 2.2 (s, 1H, –NH), 2.8–3.6 (t, 16H, eight –CH₂ groups), 7.0–8.0 (m, 4H, Ar-H). ¹³C NMR (DMSO-d₆, 400 MHz): 12.4, 29.4, 30.2, 31.7, 33.4, 34.3, 42.5, 43.6, 50.2, 51.2, 124.1, 125.2, 127.3, 129.3, 160.3, 164.2. Ms: = 331 (M+. + 1).

5f: IR (KBr): 3100–3400  (broad medium, –NH–), 1690  (sharp, strong, –CO– of amide group), 1650  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.6 (t, 3H, –CH₃), 2.2 (s, 1H, –NH), 2.8–3.6 (t, 16H, eight –CH₂ groups), 7.0–8.0 (m, 4H, Ar-H). ¹³C NMR (DMSO-d₆, 400 MHz): 28.4, 31.4, 32.5, 33.3, 35.4, 41.4, 42.4, 51.4, 52.3, 125.2, 126.1, 128.3, 129.2, 161.6, 165.1. Ms: = 317 (M+. + 1).

5g: IR (KBr): 3100–3400  (broad medium, –NH–), 1680  (sharp, strong, –CO– of amide group), 1655  (sharp, strong, –CO– of amide group); ¹H-NMR: 2.2 (s, 1H, –NH), 2.8–3.6 (t, 16H, eight –CH₂ groups), 7.0–8.0 (m, 4H, Ar-H). ¹³C NMR (DMSO-d₆, 400 MHz): 30.1, 31.3, 33.5, 34.2, 42.6, 43.8, 50.1, 51.4, 123.2, 125.1, 128.2, 129.3, 160.3, 165.3. Ms: = 304 (M+. + 1).

5h: IR (KBr): 3100–3400  (broad medium, –NH–), 1690  (sharp, strong, –CO– of amide group), 1655  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.4 (t, 3H, –CH₃), 1.8 (t, 3H, –CH₃), 2.2 (q, 2H, –CH₂), 2.8–3.6 (t, 16H, eight –CH₂ groups), 7.0–8.0 (m, 4H, Ar-H). ¹³C NMR (DMSO-d₆, 400 MHz): 13.2, 28.6, 29.5, 32.2, 33.7, 34.5, 35.4, 43.5, 44.5, 53.5, 54.6, 125.5, 126.4, 126.9, 129.5, 161.3, 165.9. Ms: = 345 (M+. + 1).

5i: IR (KBr): 3100–3400  (broad medium, –NH–), 1680  (sharp, strong, –CO– of amide group), 1650  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.4 (t, 3H, –CH₃), 2.2 (q, 2H, –CH₂), 2.8–3.6 (t, 16H, eight –CH₂ groups), 7.0–8.0 (m, 4H, Ar-H). ¹³C NMR (DMSO-d₆, 400 MHz): 13.2, 29.4, 31.2, 32.2, 33.2, 34.5, 42.7, 44.8, 50.9, 51.9, 124.3, 125.9, 127.8, 129.0, 160.7, 168.9. Ms: = 332 (M+. + 1).

5j: IR (KBr): 3100–3400  (broad medium, –NH–), 1670  (sharp, strong, –CO– of amide group), 1655  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.6 (t, 3H, –CH₃), 2.8–3.6 (t, 16H, Eight –CH₂ groups), 7.0–8.0 (m, 4H, Ar-H). 13C NMR (DMSO-d₆, 400 MHz): 28.4, 33.2, 34.7, 35.4, 39.3, 44.5, 47.6, 53.2, 55.2, 127.1, 128.2, 129.3, 129.9, 163.3, 169.4. Ms: = 318 (M+. + 1).

7a: IR (KBr): 3100–3400  (broad medium, –NH–), 1680  (sharp, strong, –CO– of acid group), 1645  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.0 (t, 6H, –CH₃, –CH₃), 3.2 (q, 2H, –CH₂), 3.4 (q, 2H, –CH₂), 7.0–8.0 (m, 9H, Ar-H), 10.6 (s, 1H, –NH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 12.2, 13.4, 37.9, 42.5, 123.4, 126.2, 127.8, 128.1, 128.5, 130.3, 134.1, 137.4, 139.1, 165.8, 169.2. Ms: = 297 (M+. + 1).

7b: IR (KBr): 3100–3400  (broad medium, –NH–), 1680  (sharp, strong, –CO– of acid group), 1645  (sharp, strong, –CO– of amide group); ¹H-NMR: 2.2 (s, 1H, –NH), 3.0 (t, 2H, –CH₂), 3.2 (t, 2H, –CH₂), 3.4 (t, 2H, –CH₂), 3.8 (t, 2H, –CH₂), 7.0–8.0 (m, 9H, Ar-H), 10.4 (s, 1H, –NH, D2O exchangeable). 13C NMR (DMSO-d₆, 400 MHz): 49.3, 50.3, 51.5, 51.3, 124.3, 124.5, 125.5, 126.4, 127.3, 128.5, 129.5, 129.9, 131.5, 163.2, 164.5. Ms: = 310 (M+. + 1).

7c: IR (KBr): 3100–3400  (broad medium, –NH–), 1690  (sharp, strong, –CO– of acid group), 1645  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.2 (t, 3H, –CH₃), 2.6 (q, 2H, –CH₂), 3.0 (t, 2H, –CH₂), 3.2 (t, 2H, –CH₂), 3.4 (t, 2H, –CH₂), 3.8 (t, 2H, –CH₂), 7.0–8.0 (m, 9H, Ar-H), 10.4 (s, 1H, –NH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 12.6, 44.5, 47.3, 48.5, 50.5, 51.3, 120.3, 122.7, 125.4, 126.3, 127.7, 128.3, 129.2, 130.9, 131.4, 160.6, 164.9. Ms: = 338 (M+. + 1).

7d: IR (KBr): 3100–3400  (broad medium, –NH–), 1690  (sharp, strong, –CO– of acid group), 1655  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.6 (t, 3H, –CH₃), 3.0 (t, 2H, –CH₂), 3.2 (t, 2H, –CH₂), 3.4 (t, 2H, –CH₂), 3.8 (t, 2H, –CH₂), 7.0–8.0 (m, 9H, Ar-H), 13.00 (s, 1H, –NH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 34.5, 46.4, 47.2, 48.6, 50.2, 121.2, 123.4, 123.9, 124.6, 125.6, 126.3, 128.2, 131.9, 132.4, 164.2, 169.2. Ms: = 324 (M+. + 1).

7e: IR (KBr): 3100–3400  (broad medium, –NH–), 1680  (sharp, strong, –CO– of acid group), 1660  (sharp, strong, –CO– of amide group); ¹H-NMR: 3.0 (t, 2H, –CH₂), 3.2 (t, 2H, –CH₂), 3.4 (t, 2H, –CH₂), 3.8 (t, 2H, –CH₂), 7.0–8.0 (m, 8H, Ar-H), 13.00 (s, 1H, –NH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 50.3, 51.3, 71.5, 72.3, 120.3, 121.2, 124.2, 125.6, 128.1, 128.9, 129.1, 129.9, 131.4, 165.1, 166.3. Ms: = 311 (M+. + 1).

7f: IR (KBr): 3100–3400  (broad medium, –NH–), 1680  (sharp, strong, –CO– of acid group), 1644  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.0 (t, 6H, –CH₃, –CH₃), 2.4 (s, 3H, –CH₃), 3.2 (q, 2H, –CH₂), 3.4 (q, 2H, –CH₂), 7.0–8.0 (m, 8H, Ar-H), 10.6 (s, 1H, –NH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 12.6, 13.8, 19.4, 39.9, 43.6, 123.6, 124.6, 125.2, 126.6, 127.6, 129.8, 131.2, 133.5, 136.5, 166.7, 168.3. Ms: = 311 (M+. + 1).

7g: IR (KBr): 3100–3400  (broad medium, –NH–), 1685  (sharp, strong, –CO– of acid group), 1655  (sharp, strong, –CO– of amide group); ¹H-NMR: 2.2 (s, 1H, –NH), 2.4 (s, 3H, –CH₃), 3.0 (t, 2H, –CH₂), 3.2 (t, 2H, –CH₂), 3.4 (t, 2H, –CH₂), 3.8 (t, 2H, –CH₂), 7.0–8.0 (m, 8H, Ar-H), 10.6 (s, 1H, –NH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 20.5, 44.5, 49.3, 50.5, 51.5, 120.2, 122.4, 123.4, 124.5, 125.3, 126.6, 128.5, 130.1, 133.5, 163.7, 166.6. Ms: = 324 (M+. + 1).

7h: IR (KBr): 3100–3400  (broad medium, –NH–), 1695  (sharp, strong, –CO– of acid group), 1655  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.2 (t, 3H, –CH₃), 2.4 (s, 3H, –CH₃), 2.6 (q, 2H, –CH₂), 3.0 (t, 2H, –CH₂), 3.2 (t, 2H, –CH₂), 3.4 (t, 2H, –CH₂), 3.8 (t, 2H, –CH₂), 7.0–8.0 (m, 8H, Ar-H), 10.6 (s, 1H, –NH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 12.2, 19.3, 44.2, 47.6, 48.3, 51.2, 52.2, 119.3, 121.3, 124.2, 124.9, 126.2, 127.1, 130.4, 131.3, 132.3, 161.1, 165.1. Ms: = 352 (M+. + 1).

7i: IR (KBr): 3100–3400  (broad medium, –NH–), 1680  (sharp, strong, –CO– of acid group), 1650  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.6 (t, 3H, –CH₃), 2.4 (s, 3H, –CH₃), 3.0 (t, 2H, –CH₂), 3.2 (t, 2H, –CH₂), 3.4 (t, 2H, –CH₂), 3.8 (t, 2H, –CH₂), 7.0–8.0 (m, 8H, Ar-H), 13.00 (s, 1H, –NH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 18.4, 35.4, 45.4, 46.3, 47.3, 51.3, 120.1, 122.2, 122.6, 124.5, 124.7, 127.4, 128.6, 131.0, 132.8, 164.6, 169.9. Ms: = 338 (M+. + 1).

7j: IR (KBr): 3100–3400  (broad medium, –NH–), 1685  (sharp, strong, –CO– of acid group), 1650  (sharp, strong, –CO– of amide group); ¹H-NMR: 2.4 (s, 3H, –CH₃), 3.0 (t, 2H, –CH₂), 3.2 (t, 2H, –CH₂), 3.4 (t, 2H, –CH₂), 3.8 (t, 2H, –CH₂), 7.0–8.0 (m, 8H, Ar-H), 13.00 (s, 1H, –NH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 17.9, 51.2, 52.0, 70.2, 72.4, 121.2, 122.4, 125.3, 126.0, 126.9, 127.0, 129.6, 130.1, 131.5, 160.4, 166.7. Ms: = 325 (M+. + 1).

7k: IR (KBr): 3100–3400  (broad medium, –NH–), 1685  (sharp, strong, –CO– of acid group), 1645  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.1 (t, 6H, –CH₃, –CH₃), 2.6 (s, 3H, –CH₃), 3.2 (q, 2H, –CH₂), 3.4 (q, 2H, –CH₂), 7.0–8.0 (m, 8H, Ar-H), 10.6 (s, 1H, –NH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 12.4, 13.5, 19.6, 40.9, 43.5, 124.6, 125.6, 126.7, 128.6, 129.4, 130.6, 131.2, 136.5, 135.5, 166.9, 168.7. Ms: = 311 (M+. + 1).

7l: IR (KBr): 3100–3400  (broad medium, –NH–), 1685  (sharp, strong, –CO– of acid group), 1655  (sharp, strong, –CO– of amide group); ¹H-NMR: 2.4 (s, 1H, –NH), 2.4 (s, 3H, –CH₃), 3.0 (t, 2H, –CH₂), 3.4 (t, 2H, –CH₂), 3.4 (t, 2H, –CH₂), 3.8 (t, 2H, –CH₂), 7.0–8.0 (m, 8H, Ar-H), 10.6 (s, 1H, –NH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 19.5, 43.4, 45.5, 52.5, 53.4, 119.3, 123.4, 123.9, 124.9, 125.5, 127.6, 128.7, 130.2, 132.5, 161.3, 166.5. Ms: = 324 (M+. + 1).

7m: IR (KBr): 3100–3400  (broad medium, –NH–), 1695  (sharp, strong, –CO– of acid group), 1655  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.4 (t, 3H, –CH₃), 2.4 (s, 3H, –CH₃), 2.6 (q, 2H, –CH₂), 3.0 (t, 2H, –CH₂), 3.2 (t, 2H, –CH₂), 3.4 (t, 2H, –CH₂), 3.8 (t, 2H, –CH₂), 7.0–8.0 (m, 8H, Ar-H), 10.4 (s, 1H, –NH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 11.23, 18.2, 42.1, 43.4, 45.2, 50.8, 51.3, 119.5, 120.4, 124.5, 126.9, 127.4, 126.1, 130.6, 131.3, 132.6, 160.1, 165.6. Ms: = 352 (M+. + 1).

7n: IR (KBr): 3100–3400  (broad medium, –NH–), 1683  (sharp, strong, –CO– of acid group), 1650  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.6 (t, 3H, –CH₃), 2.4 (s, 3H, –CH₃), 3.0 (t, 2H, –CH₂), 3.2 (t, 2H, –CH₂), 3.4 (t, 2H, –CH₂), 3.8 (t, 2H, –CH₂), 7.0–8.0 (m, 8H, Ar-H), 13.00 (s, 1H, –NH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 18.3, 36.3, 43.5, 45.2, 46.2, 50.2, 121.2, 121.1, 122.4, 124.4, 125.6, 126.3, 127.2, 130.0, 131.4, 162.6, 166.8. Ms: = 338 (M+. + 1).

7o: IR (KBr): 3100–3400  (broad medium, –NH–), 1685  (sharp, strong, –CO– of acid group), 1650  (sharp, strong, –CO– of amide group); ¹H-NMR: 2.4 (s, 3H, –CH₃), 3.0 (t, 2H, –CH₂), 3.2 (t, 2H, –CH₂), 3.4 (t, 2H, –CH₂), 3.8 (t, 2H, –CH₂), 7.0–8.0 (m, 8H, Ar-H), 13.00 (s, 1H, –NH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 18.5, 50.1, 51.6, 73.5, 74.3, 119.2, 120.2, 121.2, 122.1, 123.4, 124.1, 125.3, 127.3, 128.3, 163.5, 167.4. Ms: = 325 (M+. + 1).

7p: IR (KBr): 3100–3400  (broad medium, –NH–), 1670  (sharp, strong, –CO– of acid group), 1655  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.0 (t, 6H, –CH₃, –CH₃), 2.4 (s, 3H, –CH₃), 3.2 (q, 2H, –CH₂), 3.4 (q, 2H, –CH₂), 7.0–8.0 (m, 8H, Ar-H), 10.6 (s, 1H, –NH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 12.4, 14.4, 32.9, 40.5, 121.4, 125.8, 126.8, 129.1, 130.3, 131.4, 134.6, 138.4, 139.9, 163.6, 169.9. Ms: = 331 (M+. + 1).

7q: IR (KBr): 3100–3400  (broad medium, –NH–), 1684  (sharp, strong, –CO– of acid group), 1650  (sharp, strong, –CO– of amide group); ¹H-NMR: 2.2 (s, 1H, –NH), 2.4 (s, 3H, –CH₃), 3.0 (t, 2H, –CH₂), 3.2 (t, 2H, –CH₂), 3.4 (t, 2H, –CH₂), 3.8 (t, 2H, –CH₂), 7.0–8.0 (m, 8H, Ar-H), 10.4 (s, 1H, –NH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 44.5, 44.9, 53.2, 54.2, 119.6, 120.5, 121.9, 122.9, 127.5, 128.5, 129.6, 130.2, 131.3, 162.4, 164.2. Ms: = 344 (M+. + 1).

7r: IR (KBr): 3100–3400  (broad medium, –NH–), 1650  (sharp, strong, –CO– of acid group), 1640  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.2 (t, 3H, –CH₃), 2.4 (s, 3H, –CH₃), 2.6 (q, 2H, –CH₂), 3.0 (t, 2H, –CH₂), 3.2 (t, 2H, –CH₂), 3.4 (t, 2H, –CH₂), 3.8 (t, 2H, –CH₂), 7.0–8.0 (m, 8H, Ar-H), 10.4 (s, 1H, –NH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 12.8, 44.2, 45.4, 46.2, 51.8, 52.4, 119.6, 121.5, 124.5, 125.6, 127.3, 125.6, 130.2, 132.4, 135.7, 160.7, 165.9. Ms: = 372 (M+. + 1).

7s: IR (KBr): 3100–3400  (broad medium, –NH–), 1640  (sharp, strong, –CO– of acid group), 1635  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.6 (t, 3H, –CH₃), 2.4 (s, 3H, –CH₃), 3.0 (t, 2H, –CH₂), 3.2 (t, 2H, –CH₂), 3.4 (t, 2H, –CH₂), 3.8 (t, 2H, –CH₂), 7.0–8.0 (m, 8H, Ar-H), 13.00 (s, 1H, –NH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 38.3, 45.6, 46.2, 47.5, 50.6, 123.2, 126.6, 127.3, 128.3, 129.1, 129.9, 130.2, 131.4, 132.4, 160.3, 166.4. Ms: = 358 (M+. + 1).

7t: IR (KBr): 3100–3400  (broad medium, –NH–), 1690  (sharp, strong, –CO– of acid group), 1650  (sharp, strong, –CO– of amide group); ¹H-NMR: 2.4 (s, 3H, –CH₃), 3.0 (t, 2H, –CH₂), 3.2 (t, 2H, –CH₂), 3.4 (t, 2H, –CH₂), 3.8 (t, 2H, –CH₂), 7.0–8.0 (m, 8H, Ar-H), 13.00 (s, 1H, –NH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 48.1, 50.6, 72.5, 73.1, 119.5, 120.6, 122.3, 122.9, 123.5, 124.3, 125.7, 126.3, 129.3, 165.7, 169.4. Ms: = 345 (M+. + 1).

7u: IR (KBr): 3100–3400  (broad medium, –NH–), 1680  (sharp, strong, –CO– of acid group), 1650  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.0 (t, 6H, –CH₃, –CH₃), 2.4 (s, 3H, –CH₃), 3.2 (q, 2H, –CH₂), 3.4 (q, 2H, –CH₂), 7.0–8.0 (m, 9H, Ar-H), 10.6 (s, 1H, –NH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 12.5, 15.4, 37.9, 43.5, 125.4, 126.5, 126.8, 129.6, 131.2, 131.3, 135.6, 138.6, 139.3, 164.6, 169.8. Ms: = 375 (M+. + 1).

7v: IR (KBr): 3100–3400  (broad medium, –NH–), 1687  (sharp, strong, –CO– of acid group), 1655  (sharp, strong, –CO– of amide group); ¹H-NMR: 2.2 (s, 1H, –NH), 2.4 (s, 3H, –CH₃), 3.0 (t, 2H, –CH₂), 3.2 (t, 2H, –CH₂), 3.4 (t, 2H, –CH₂), 3.8 (t, 2H, –CH₂), 7.0–8.0 (m, 9H, Ar-H), 13.00 (s, 1H, –NH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 41.5, 45.9, 52.3, 54.5, 118.4, 121.3, 125.9, 126.9, 127.7, 128.4, 129.7, 131.4, 133.5, 165.4, 167.7. Ms: = 388 (M+. + 1).

7w: IR (KBr): 3100–3400  (broad medium, –NH–), 1681  (sharp, strong, –CO– of acid group), 1655  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.2 (t, 3H, –CH₃), 2.4 (s, 3H, –CH₃), 2.6 (q, 2H, –CH₂), 3.0 (t, 2H, –CH₂), 3.2 (t, 2H, –CH₂), 3.4 (t, 2H, –CH₂), 3.8 (t, 2H, –CH₂), 7.0–8.0 (m, 9H, Ar-H), 10.4 (s, 1H, –NH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 12.4, 43.5, 45.7, 47.3, 52.9, 53.4, 118.4, 121.6, 124.7, 125.5, 128.3, 129.5, 130.5, 131.3, 135.4, 164.5, 165.9. Ms: = 416 (M+. + 1).

7x: IR (KBr): 3100–3400  (broad medium, –NH–), 1690  (sharp, strong, –CO– of acid group), 1658  (sharp, strong, –CO– of amide group); ¹H-NMR: 1.6 (t, 3H, –CH₃), 2.4 (s, 3H, –CH₃), 3.0 (t, 2H, –CH₂), 3.2 (t, 2H, –CH₂), 3.4 (t, 2H, –CH₂), 3.8 (t, 2H, –CH₂), 7.0–8.0 (m, 9H, Ar-H), 13.00 (s, 1H, –NH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 39.2, 46.4, 47.3, 48.4, 49.5, 121.2, 124.3, 124.9, 125.7, 126.4, 128.3, 130.6, 131.1, 131.3, 166.1, 169.3. Ms: = 402 (M+. + 1).

7y: IR (KBr): 3100–3400  (broad medium, –NH–), 1675  (sharp, strong, –CO– of acid group), 1635  (sharp, strong, –CO– of amide group); ¹H-NMR: 2.4 (s, 3H, –CH₃), 3.0 (t, 2H, –CH₂), 3.2 (t, 2H, –CH₂), 3.4 (t, 2H, –CH₂), 3.8 (t, 2H, –CH₂), 7.0–8.0 (m, 9H, Ar-H), 13.00 (s, 1H, –NH, D2O exchangeable). ¹³C NMR (DMSO-d₆, 400 MHz): 48.9, 51.4, 73.5, 74.5, 119.6, 121.4, 122.5, 123.8, 124.7, 125.7, 126.4, 127.3, 129.3, 165.8, 169.3. Ms: = 389 (M+. + 1).

Conflict of Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.

Acknowledgment

The authors are thankful to the authorities of Jawaharlal Nehru Technological University Hyderabad for providing laboratory facilities and for financial support to two of the authors (Padam Praveen Kumar and Yervala Dathu Reddy).

References

O. R. Louis and R. G. Harry, “Alcoholysis of alkyl benzyl esters of phthalic acid,” The Journal of Organic Chemistry, vol. 24, no. 12, pp. 1997–2000, 1959.

P. K. Dubey, S. M. G. Mohiuddin, and D. Ramesh, “Reactions of phthalic anhydride with alcohols,” Asian Journal of Chemistry, vol. 9, no. 3, pp. 379–387, 1997.

P. A. Kober, J. T. Marshall, and E. N. Rosenfeld, “Phenolphthalein and its colorless salts. [Third paper.]. Preparation of monobasic phenolphthalates,” Journal of the American Chemical Society, vol. 34, no. 10, pp. 1424–1433, 1912.

D. Williamm, “Salts of phenolphthalein,” Journal of the American Chemical Society, vol. 54, no. 7, pp. 2947–2951, 1932.

S. A. Carlson and D. M. Hercules, “Delayed thermal fluorescence of anthraquinone in solutions,” Journal of the American Chemical Society, vol. 93, no. 22, pp. 5611–5616, 1971.

L. Lunazzi, M. Mancinelli, and A. Mazzani, “Stereodynamics and conformational chirality of the atropisomers of ditolyl anthrones and anthraquinone,” The Journal of Organic Chemistry, vol. 73, no. 14, pp. 5354–5359, 2008.

D. Guay, G. Tourillon, L. Gastonguay et al., “Highly photoactive chemically modified thin films of chloroaluminum (and bromoaluminum) phthalocyanines probed by NEXAFS and UPS: determination of the electronic structure and the molecular orientation,” Journal of Physical Chemistry, vol. 95, no. 1, pp. 251–257, 1991.

P. K. Dubey, S. M. G. Mohiuddin, and D. Ramesh, “Assay of phthalic anhydride and some related compounds by volumetric methods,” Asian Journal of Chemistry, vol. 7, no. 3, pp. 597–603, 1995.

L. O. Okunrobo, C. O. Usifoh, and S. O. Okpo, “Reactions of phthalimides with 1-methylethylamine: analgesic and anti-inflammatory properties of resulting carboxamides,” Pakistan Journal of Pharmaceutical Sciences, vol. 19, no. 1, pp. 34–38, 2006.

V. K. Pandey and N. Raj, “Synthesis of α-methylarylamido-β-naphthyl-(1-methylamino-2-methyl-benzimi-dazolyl)-ethers,” Current Science, vol. 53, no. 5, pp. 256–258, 1984.

A. M. Alaa and A. Abdel, “Novel and versatile methodology for synthesis of cyclic imides and evaluation of their cytotoxic, DNA binding, apoptotic inducing activities and molecular modeling study,” European Journal of Medicinal Chemistry, vol. 42, no. 5, pp. 614–626, 2007.

F. L. Dunlap and F. W. Cummer, “The action of the sodium salts of dibasic acids on aniline hydrochloride, and of aniline on phthalyl chloride and succinyl chloride,” Journal of the American Chemical Society, vol. 25, no. 6, pp. 612–621, 1903.

A. T. Dann, W. Davies, A. N. Hambly, R. E. Paul, and G. S. C. Semmens, “Phthalyl fluoride,” Journal of the Chemical Society, pp. 15–21, 1933.

E. G. D. de Toranzo and J. A. Brieux, “Syntheses of unsymmetric o-phthalic acid diamides,” Journal of Medicinal Chemistry, vol. 10, no. 5, pp. 982–983, 1967.

A. Reynolds, “Synthesis and characterization of some toluides of o-phthalic acid,” The Journal of Organic Chemistry, vol. 28, no. 11, pp. 3223–3225, 1963.

A. El-Faham and F. Albericio, “Peptide coupling reagents, more than a letter soup,” Chemical Reviews, vol. 111, no. 11, pp. 6557–6602, 2011.

L. A. Carpino and A. El-Faham, “Tetramethylfluoroformamidinium hexafluorophosphate: a rapid-acting peptide coupling reagent for solution and solid phase peptide synthesis,” Journal of the American Chemical Society, vol. 117, no. 19, pp. 5401–5402, 1995.

R. Subiros-Funosas, G. A. Acosta, A. El-Faham, and F. Albericio, “Microwave irradiation and COMU: a potent combination for solid-phase peptide synthesis,” Tetrahedron Letters, vol. 50, no. 45, pp. 6200–6202, 2009.

S.-Y. Han and Y.-A. Kim, “Recent development of peptide coupling reagents in organic synthesis,” Tetrahedron, vol. 60, no. 11, pp. 2447–2467, 2004.