An expeditious synthesis of imides from phthalic, maleic and succinic anhydrides and chemoselective C=C reduction of maleic amide esters

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1 Indian Journal of Chemistry Vol. 53B, April 2014, pp An expeditious synthesis of imides from phthalic, maleic and succinic anhydrides and chemoselective C=C reduction of maleic amide esters Padam Praveen Kumar*, Y Dathu Reddy, Y Bharathi Kumari, B Rama Devi & P K Dubey Department of Chemistry, College of Engineering, Jawaharlal Nehru Technological University Kukatpally, Hyderabad 500 0, India padampraveenku@gmail.com Received 26 November 2012; accepted (revised) 22 January 2014 Phthalic, maleic and succinic anhydrides have been reacted with aromatic amines to obtain the corresponding monoacid monoamides. The latter have been each transformed into the corresponding cyclic imide derivatives by treating with SOCl 2. Alternatively, anhydrides have been reacted with methanolic KOH to obtain monomethyl ester derivatives which on reaction with aromatic amines in the presence of EDC. HCl and HOBt give cyclic imide derivatives. Reaction of monoacid monoamides independently, with SOCl 2 at 0-5 C give the monoamide monoester derivatives. Treatment of monoamide monoester of malic anhydride with NaBH 4 leads to the unusual reduction of C=C grouping as well as the carbonyl group of the ester group to from monoamide monoalcohol of succinic anhydride. Preparation of monoamide monoalcohol of succinic anhydride can also be achieved by chemoselective reduction of monoamide monoester of malic anhydride with Mg turnings yielding monoamide monoester of succinic anhydride followed by reduction of the latter with NaBH 4. Keywords: Phthalic anhydride, maleic anhydride, succinic anhydride, Mg turnings Imide derivatives are a valuable group of bioactive compounds showing anti-inflammatory 1, antiviral 2, antibacterial 3 and antitumor 4 properties. In spite of their wide applicability, available procedures for their synthesis are limited 5. Among them, the dehydrative condensation of an anhydride with an amine in the presence of many reagents is most commonly used 6. Many catalysts including hexamethyldisilazane 7, diphenyl 2-oxo-3-oxazolidinylphosponate (DPPOx) 8 and ionic liquid [bmim][pf 6 ] 9 have been proposed for the synthesis of cyclic imides. However, each of these routes has its own merits and de-merits. In addition, microwave assisted synthesis of imides has also been reported. However, Westaway and Gedye 11 did not see any differences when the reaction was carried out by microwave or conventional heating in DMF. Therefore, it was considered worthwhile to synthesis of cyclic imides. In continuation of the earlier work 12 on synthesis of imides, it was felt necessary to develop alternative methods for the preparation of imides under mild conditions. Herein is described an expeditious and in situ cyclisation of amidic acid ester in the presence of SOCl 2 to prepare corresponding imide derivatives under mild conditions. This approach requires only a few minutes of reaction time, in contrast to conventional method 12 that requires several hours of reaction time and expensive catalysts. Results and Discussion Reactions of phthalic 1, maleic 7 and succinic 12 anhydrides with aniline 2 in acetic acid at RT for about -20 minutes resulted in the formation of monoacid monoamide derivatives 12 3, 8 and 13 respectively. The latter were each on reaction with SOCl 2 at RT in alcohol for min converted to the corresponding cyclic imides 5, and. Alternatively, 1, 7 and 12 in alcoholic KOH at RT for min gave the mono methyl ester derivatives 13,14 of the corresponding anhydrides 6, 11 and 16. Each one of the latter, on reaction with aromatic amine 2, in the presence of 1-ethyl-3-(3- dimethyllaminopropyl)-carbodiimide hydrochloride (EDC.HCl) and catalytic amount of N-hydroxybenzotriazole (HOBt) for about min at 0 C, resulted in the formation of corresponding cyclic imides 5, and (Scheme I, Table I). The monoacid monoamide derivatives of maleic 8 and succinic 13 anhydrides on reaction with SOCl 2 at 0-5 C resulted in the formation of monoamide monoester 9 and 14 respectively. Alternatively, 8 and 14 could also be prepared by the reaction of 11 and 16 with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC.HCl) and catalytic amount of N-hydroxybenzotriazole (HOBt) for about min at 0- C. The structures of these products have been established on the basis of their spectral and analytical data (Scheme I, Table II).

2 KUMAR et al.: IMIDES FROM PHTHALIC, MALEIC AND SUCCINIC ANHYDRIDES 393 Scheme I It thus appears, that in the transformation of 3 to 5 or of 8 to or of 13 to, initially with SOCl 2 in alcohol at 0-5 C, the intermediary ester amide (4, 9 and 14) are formed which transform into 5, or respectively on reaction with SOCl 2 at RT in alcohol (Scheme I). In the case of maleic 7 and succinic 12 anhydrides the intermediates 9 and 14 could be isolated and characterised. However, in case of phthalic anhydride 1, the intermediary 4 could not be isolated and characterised, probably due to its highly reactive nature, quickly forcing ring closure giving rise to 5 (Scheme I, Table II). The above reactions in two methods have been found to be general ones and have been extended to different anilines 2 and structure of the products 5, and thus obtained were assigned by comparison with authentic samples 12. Treatment of 9 with NaBH 4 at RT for min in methanol led to the unusual reduction of C=C grouping as well as the carbonyl group of the ester group in N-aryl-4-hydroxybutanamide 17. Compound 17 could also be synthesized in a step-wise fashion. Treatment of 9 with Mg turnings in ethanol at RT for about 2-4 h, followed by simple processing resulted in the formation of 14 which was found to be identical with the one obtained earlier in the step-wise route (i.e ). Compound 14 on reduction with NaBH 4 in methanol at RT for min yielded 17 (Scheme II, Table III). Experimental Section Melting points are uncorrected and were determined in open capillary tubes in sulphuric acid bath. TLC were run on silica gel-g and visualization was achieved using iodine vapour or UV light. IR spectra were recorded using Perkin-Elmer 00 instrument in KBr pellets. 1 H NMR spectra were recorded in CDCl 3 /DMSO-d 6 using TMS as internal standard with 400 MHz spectrometer. Mass spectra were recorded on Agilent-LCMS instrument under CI conditions and described by Q+1 values only. General procedure for the preparation of 4/9/14 from 3/8/13 To a solution of 3/8/13 ( mm) in alcohol (- ml) at 0-5 C was added thionyl chloride ( mm). The reaction mixture was stirred well for 5- min. The completion of the reaction was checked by TLC. Then, ice-cold water was added to the reaction mixture, the separated solid was filtered, washed with water (2 ml) and dried. The product was recrystallised from ethanol to obtain 4/9/14 respectively. General procedure for the preparation of 5// from 3/8/13 To a solution of 3/8/13 ( mm) in alcohol (- ml) at RT was added thionyl chloride ( mm). The reaction mixture was stirred well for

3 394 INDIAN J. CHEM., SEC B, APRIL 2014 Table I Reaction time and yields of 5// obtained from 3/8/13 and 6 Product obtained 5a 5b 5c 5d 5e 5f a b c d e f a b c d e f Time Yield* (min) (%) m.p. ( C) (Ref) (Ref 12) (Ref 12) 1-82 (Ref 12) (Ref 12) (Ref 12) (Ref 12) >220 (Ref 12) (Ref 12) (Ref 12) >200 (Ref 12) 4-56 (Ref 12) >2 (Ref 12) 1-12 (Ref 12) (Ref 12) (Ref 12) (Ref 12) (Ref 12) (Ref 12) min. The completion of the reaction was checked by TLC. Then, ice-cold water was added to the reaction mixture, the separated solid was filtered, washed with water (2 ml) and dried. The product was recrystallised from acetic acid to obtain 5// respectively. General procedure for the preparation of 4/9/14 from 6/11/16 To a solution of 6/11/16 ( mm) in DMF ( ml) was added aniline (11 mm), HOBt ( mm) and triethyl amine ( mm). To this mixture EDC.HCl was added at 0-5 C and this reaction mixture stirred well for min. The completion of the reaction was checked by TLC. Then, ice-cold water was added to the reaction mixture, the separated solid was filtered, washed with water (2 ml) and dried. The Table II Reaction time and yields of 9/14 obtained from 8/13 or 11/16 at 0-5 C Product obtained R/Ar Time (min) Yield* (%) m.p. ( C) 9a CH g C 2 H b CH h C 2 H c CH i C 2 H d CH j C 2 H e CH 3 70 liquid 9k C 2 H f CH l C 2 H a CH g C 2 H b CH h C 2 H c CH i C 2 H d CH j C 2 H e CH k C 2 H f CH l C 2 H a -C 6 H b -C 6 H 4 -CH 3 -(p) c -C 6 H 4 -CH 3 -(o) 8-1 9d -C 6 H 4 -Cl-(p) e -C 6 H 4 -OCH 3 -(p) Liquid 9f -C 6 H 4 -Br-(p) a -C 6 H b -C 6 H 4 -CH 3 -(p) c -C 6 H 4 -CH 3 -(o) d -C 6 H 4 -Cl-(p) e -C 6 H 4 -OCH 3 -(p) f -C 6 H 4 -Br-(p) * Refers to yields of crude products only product was recrystallised from ethanol to obtain 4/9/14 respectively. General procedure for the preparation of 5// from 6/11/16 To a solution of 6/11/16 ( mm) in DMF ( ml) was added aniline (11 mm), HOBt ( mm) and triethyl amine ( mm) at RT. To this mixture EDC.HCl (11 mm) was added at 0-5 C and this reaction mixture heated at 0 C for min. The completion of the reaction was checked by TLC. Then, ice-cold water was added to the reaction mixture, the separated solid was filtered, washed with

4 KUMAR et al.: IMIDES FROM PHTHALIC, MALEIC AND SUCCINIC ANHYDRIDES 395 Scheme II Table III Reaction time and yields of 17 obtained from 9 Product obtained Yield*(%) Route 1 Route 2 m.p. ( C) 17a b c d e f a b c d e f * Refers to yields of crude products only water (2 ml) and dried. The product was recrystallised from acetic acid to obtain 5// respectively. General procedure for the preparation of 17 from 9 To a solution of 9 ( mm) in methanol (-20 ml) at RT was added sodium borohydride (11 mm). The reaction mixture was stirred well for about min and this solution was poured into ice-cold water. The separated solid was filtered, washed with water (8- ml) followed by a little amount of alcohol (2-5 ml), then dried. This product was recrystallised from ethanol to obtain pure 17. General procedure for the preparation of 14 from 9 To a solution of 9 ( mm) in methanol (-20 ml) at RT was added a solution of Mg in methanol (5- ml). The reaction mixture was stirred well for about 1-3 hr and then poured into ice-cold water. The separated solid was filtered, washed with water (8- ml) followed by a little amount of alcohol (2-5 ml) and dried. The crude product was recrystallised from ethanol to obtain pure 14. General procedure for the preparation of 17 from 14 To a solution of 14 ( mm) in methanol (-20 ml) at RT was added sodium borohydride (11 mm). The reaction mixture was stirred well for about 5- min and this solution was poured into ice-cold water. The separated solid was filtered, washed with water (8- ml) followed by a little amount of alcohol (2-5 ml), then dried. This product was recrystallised from ethanol to obtain pure 17. Spectral Data for Compounds 9a: IR (KBr): 1658 (-C=O of amide group), 1723 (-C=O of ester group), cm -1 (broad,-nh of δ 3.8 (s, 3H,-OCH 3 ), (d, 2H, alkene protons), (m, 5H corresponds to aromatic protons),.0 (s, 1H,-NH); MS: m/z 206 9b: IR (KBr): 1641 (-C=O of amide group), 17 (-C=O of ester group), cm -1 (broad, -NH of δ 2.34 (s, 3H,-CH 3 ), 3.8 (s, 3H,-OCH 3 ), (d, 2H, alkene protons), (m, 4H corresponds to aromatic protons),.1 (s, 1H,-NH); MS: m/z 220 9c: IR (KBr): 1641 (-C=O of amide group), 17 (-C=O of ester group), cm -1 (broad, -NH of δ 2.34 (s, 3H,-CH 3 ), 3.8 (s, 3H,-OCH 3 ), (d,

5 396 INDIAN J. CHEM., SEC B, APRIL H, alkene protons), (m, 4H corresponds to aromatic protons),.4 (s, 1H,-NH); MS: m/z 220 9d: IR (KBr): 1658 (-C=O of amide group), 1724 (-C=O of ester group), cm -1 (broad, -NH of δ 3.8 (s, 3H,-OCH 3 ), (d, 2H, alkene protons), (m, 4H corresponds to aromatic protons), 11.1 (s, 1H,-NH); MS: m/z 240 9e: IR (KBr): 1641 (-C=O of amide group), 17 (-C=O of ester group), cm -1 (broad, -NH of δ 2.34 (s, 3H,-CH 3 ), 3.8 (s, 3H,-OCH 3 ), 4.1 (s, 3H, -OCH 3 ) (d, 2H, alkene protons), (m, 4H corresponds to aromatic protons),.1 (s, 1H, -NH); MS: m/z 236 9f: IR (KBr): 1658 (-C=O of amide group), 1723 (-C=O of ester group), cm -1 (broad, -NH of δ 3.8 (s, 3H,-OCH 3 ), (d, 2H, alkene protons), (m, 4H corresponds to aromatic protons), 11.0 (s, 1H,-NH); MS: m/z 283 9g: IR (KBr): 1655 (-C=O of amide group), 17 (-C=O of ester group), cm -1 (broad, -NH of δ 1.3 (t, 3H,-CH 3 ) 4.1 (q, 2H,-OCH 2 ), (d, 2H, alkene protons), (m, 5H corresponds to aromatic protons), 9.8 (s, 1H,-NH); MS: m/z 220 9h: IR (KBr): 1641 (-C=O of amide group), 17 (-C=O of ester group), cm -1 (broad, -NH of δ 1.2 (t, 3H,-CH 3 ), 2.4 (s, 3H,-CH 3 ), 4.2 (q, 2H, -OCH 3 ), (d, 2H, alkene protons), (m, 4H corresponds to aromatic protons), 11.1 (s, 1H, -NH); MS: m/z 234 9i: IR (KBr): 1645 (-C=O of amide group), 1724 (-C=O of ester group), cm -1 (broad, -NH of δ 1.3 (t, H,-CH 3 ), 2.5 (s, 3H,-CH 3 ), 3.8 (q, 2H, -OCH 2 ), (d, 2H, alkene protons), (m, 4H corresponds to aromatic protons),.4 (s, 1H, -NH); MS: m/z 234 9j: IR (KBr): 1652 (-C=O of amide group), 1724 (-C=O of ester group), cm -1 (broad, -NH of δ 1.3 (t, 3H,-CH 3 ), 4.3 (q, 2H,-OCH 2 ), (d, 2H, alkene protons), (m, 4H corresponds to aromatic protons), 11.1 (s, 1H,-NH); MS: m/z 4 9k: IR (KBr): 1641 (-C=O of amide group), 17 (-C=O of ester group), cm -1 (broad, -NH of δ 1.4 (t, 3H,-CH 3 ), 3.8 (s, 3H,-OCH 3 ), 4.2 (q, 2H, -OCH 2 ) (d, 2H, alkene protons), (m, 4H corresponds to aromatic protons),.1 (s, 1H, -NH); MS: m/z 0 9l: IR (KBr): 1658 (-C=O of amide group), 1724 (-C=O of ester group), cm -1 (broad, -NH of δ 1.3 (t, H,-CH 3 ), 4.2 (q, 2H,-OCH 2 ), (d, 2H, alkene protons), (m, 4H corresponds to aromatic protons), 11.2 (s, 1H,-NH); MS: m/z a: IR (KBr): 1686 (-C=O of amide group), 1723 (-C=O of ester group), 3360 cm -1 (broad, -NH of δ 3.6 (s, 3H,-OCH 3 ), 2.6 (s, 4H,-CH 2 -CH 2 -), (m, 5H corresponds to aromatic protons),.0 (s, 1H, -NH); MS: m/z b: IR (KBr): 1686 (-C=O of amide group), 17 (-C=O of ester group), cm -1 (broad, -NH of δ 2.34 (s, 3H,-CH 3 ), 3.7 (s, 3H,-OCH 3 ), 2.6 (s, 4H, -CH 2 -CH 2 -), (m, 4H corresponds to aromatic protons), 9.7 (s, 1H,-NH); MS: m/z c: IR (KBr): 1665 (-C=O of amide group), 1723 (-C=O of ester group), cm -1 (broad, -NH of δ 2.34 (s, 3H,-CH 3 ), 3.8 (s, 3H,-OCH 3 ), (t, 4H,-CH 2 -CH 2 -), (m, 4H corresponds to aromatic protons), 8.2 (s, 1H,-NH); MS: m/z d: IR (KBr): 1676 (-C=O of amide group), 1724 (-C=O of ester group), cm -1 (broad, -NH of 3.8 (s, 3H,-OCH 3 ), (t, 4H,-CH 2 -CH 2 -), (m, 4H corresponds to aromatic protons), (s, 1H,-NH); MS: m/z e: IR (KBr): 1686 (-C=O of amide group), 17 (-C=O of ester group), cm -1 (broad, -NH of δ 2.34 (s, 3H,-CH 3 ), 3.8 (s, 3H,-OCH 3 ), 4.1 (s, 3H, -OCH 3 ), 2.6 (s, 4H,-CH 2 -CH 2 -), (m, 4H corresponds to aromatic protons),.1 (s, 1H,-NH); MS: m/z f: IR (KBr): 1658 (-C=O of amide group), 1724 (-C=O of ester group), cm -1 (broad, -NH of δ 3.8 (s, 3H,-OCH 3 ), 2.8 (s, 4H,-CH 2 -CH 2 -), (m, 4H corresponds to aromatic protons),.5 (s, 1H, -NH); MS: m/z 2

6 KUMAR et al.: IMIDES FROM PHTHALIC, MALEIC AND SUCCINIC ANHYDRIDES g: IR (KBr): 1686 (-C=O of amide group), 1723 (-C=O of ester group), 3360 cm -1 (sharp, -NH of δ 1.3 (t, 3H,-CH 3 ), 4.2 (q, 2H,-OCH 2 ), 2.6 (s, 4H,- CH 2 -CH 2 -), (m, 5H corresponds to aromatic protons), 8.3 (s, 1H,-NH); MS: m/z h: IR (KBr): 1670 (-C=O of amide group), 17 (-C=O of ester group), cm -1 (broad, -NH of δ 1.2 (t, 3H,-CH 3 ), 2.4 (s, 3H,-CH 3 ), 4.2 (q, 2H, -OCH 3 ), (t, 4H,-CH 2 -CH 2 -), (m, 4H corresponds to aromatic protons), 8.9 (s, 1H,-NH); MS: m/z i: IR (KBr): 1670 (-C=O of amide group), 17 (-C=O of ester group), cm -1 (broad, -NH of δ 1.2 (t, 3H,-CH 3 ), 2.4 (s, 3H,-CH 3 ), 4.2 (q, 2H, -OCH 3 ), 2.6 (s, 4H,-CH 2 -CH 2 -), (m, 4H corresponds to aromatic protons), 8.9 (s, 1H,-NH); MS: m/z j: IR (KBr): 1686 (-C=O of amide group), 1724 (-C=O of ester group), 3360 cm -1 (sharp, -NH of δ 1.3 (t, 3H,-CH 3 ), 4.2 (q, 2H,-OCH 2 ), (t, 4H,-CH 2 -CH 2 -), (m, 4H corresponds to aromatic protons), 7.9 (s, 1H,-NH); MS: m/z 6 14k: IR (KBr): 1686 (-C=O of amide group), 17 (-C=O of ester group), cm -1 (broad, -NH of δ 1.4 (t, 3H,-CH 3 ), 3.8 (s, 3H,-OCH 3 ), 4.2 (q, 2H, -OCH 2 ), (t, 4H,-CH 2 -CH 2 -), (m, 4H corresponds to aromatic protons), 8.1 (s, 1H,-NH); MS: m/z 2 14l: IR (KBr): 1686 (-C=O of amide group), 1724 (-C=O of ester group), 3360 cm -1 (sharp, -NH of δ 1.3 (t, 3H,-CH 3 ), 4.2 (q, 2H,-OCH 2 ), (t, 4H,- CH 2 -CH 2 -), (m, 4H corresponds to aromatic protons), 7.9 (s, 1H,-NH); MS: m/z 0 17a: IR (KBr): 1683 (-C=O of amide group), 3365 (broad, -NH of amide group), cm -1 (broad, -OH of amide group); 1 H NMR (400 MHz, CDCl 3 /TMS): δ (t, 4H,-CH 2 -CH 2 ), 3.4 (d, 2H, -CH 2 ), 4.5 (s, 1H,-OH), (m, 5H corresponds to aromatic protons),.0 (s, 1H,-NH); MS: m/z 1 17b: IR (KBr): 1682 (-C=O of amide group), (broad, -NH of amide group), cm -1 CDCl 3 /TMS): δ (t, 4H,-CH 2 -CH 2 ), 2.3 (s, 3H, -CH 3 ), 3.4 (d, 2H,-CH 2 ), 4.6 (s, 1H,-OH), (m, 4H corresponds to aromatic protons), 9.7 (s, 1H,-NH); MS: m/z c: IR (KBr): 1664 (-C=O of amide group), (broad, -NH of amide group), cm -1 CDCl 3 /TMS): δ (t, 4H,-CH 2 -CH 2 ), 2.3 (s, 3H, -CH 3 ), 3.4 (d, 4H,-CH 2 ),4.5 (s, 1H,-OH), (m, 4H corresponds to aromatic protons), 8.2 (s, 1H,-NH); MS: m/z d: IR (KBr): 1674 (-C=O of amide group), (broad, -NH of amide group), cm -1 CDCl 3 /TMS): δ (t, 4H,-CH 2 -CH 2 ), 3.4 (d, 4H, -CH 2 ), 4.4 (s, 1H,-OH), (m, 4H corresponds to aromatic protons), (s, 1H,-NH); MS: m/z e: IR (KBr): 1690 (-C=O of amide group), - 30 (broad, -NH of amide group), cm -1 CDCl 3 /TMS): δ (t, 4H,-CH 2 -CH 2 ), (s, 3H,-OCH 3 ), 3.4 (d, 4H,-CH 2 ), 4.3 (s, 1H,-OH), (m, 4H corresponds to aromatic protons),.1 (s, 1H, -NH); MS: m/z 2 17f: IR (KBr): 1660 (-C=O of amide group), - 32 (broad, -NH of amide group), cm -1 CDCl 3 /TMS): δ (t, 4H,-CH 2 -CH 2 ), 3.4 (d, 2H, -CH 2 -), 4.2 (s, 1H,-OH), (m, 4H corresponds to aromatic protons),.5 (s, 1H,-NH); MS: m/z 9 Conclusion In conclusion, herein is described an expeditious and in situ cyclisation of amidic acid ester in the presence of SOCl 2 for the preparation of the corresponding imide derivatives under mild conditions and chemoselective C=C reduction of maleic amide esters. This approach requires only a few minutes of reaction time. The present method has many obvious advantages compared to those reported in literature, including simplicity of the methodology and ease of product isolation with good yield. Acknowledgements Authors are thankful to the authorities of Jawaharlal Nehru Technological University, Hyderabad for providing laboratory facilities and for constant encouragement.

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