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A new and facile synthetic approach to substituted 2-thioxoquinazolin-4-ones by the annulation of a pyrimidine derivative

Nimalini D. Moirangthem and Warjeet S. Laitonjam
Department of Chemistry, Manipur University, Canchipur 795 003, Manipur, India
Email of author Author email      Email of corresponding author Corresponding author email     
Associate Editor: I. Marek
Beilstein J. Org. Chem. 2010, 6, 1056–1060.
doi:10.3762/bjoc.6.120
 
 
 
 

Abstract

A new and facile synthesis of 2-thioxoquinazolin-4-ones by introducing a benzenoid system in the pyrimidine moiety by reacting ethoxymethylene derivatives of 1,3-diarylthiobarbituric acids (DTBA) with active methylene compounds, such as malononitrile and ethyl cyanoacetate, in presence of ZnCl2 has been developed.

Keywords: benzenoid; ethylcyanoacetate; malononitrile; pyrimidine; 2-thioxoquinazolin-4-ones

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Introduction

Quinazolines and derivatives are of much interest due to their biological activities [1,2]. Additionally, quinazolines are interesting targets for new method development due to their importance in numerous therapeutic areas. Recently, antitumor [3] and anti-HIV activities [4,5] of quinazolines have been described. A large number of quinazoline derivatives, which contain the 4-oxo-2-thioxo-1,2,3,4-tetrahydropyrimidine structural moiety in their heterocyclic rings, possess a wide range of biological activities [6-8]. There are a number of synthetic methods available for the preparation of quinazolines [9]. The most common synthetic route involves the amidation of 2-aminobenzoic acid or its derivatives, i.e., 2-aminobenzonitrile, 2-aminobenzoates, and 2-arylnitrilium salts, followed by oxidative ring closure [10-13]. Other synthetic pathways include the cyclization of anthranilamides with aldehydes [14], and with ketones or acid chlorides under acidic or basic conditions [15-17]. However, most of the methods involve multistep processes and time-consuming experimental procedures, and give poor yields or use toxic reagents. Moreover, very few methods are reported for the synthesis of 2-thioxoquinazolin-4-ones, as most of the methods reported are for quinazolin-2,4(1H,3H)-diones. Recently, Saeed et al. [18] reported the base catalyzed intramolecular nucleophilic cyclization of substituted thioureas in the presence of DMF to afford 2-thioxoquinazolin-4-ones. The preparation of 2-thioxoquinazolin-4-one libraries by solid-phase synthesis has been reported [19-21].

There are two approaches for the solution-phase parallel synthesis of 2-thioxoquinazolin-4-ones [22]. The first approach is based on the reaction of methyl anthranilates with isothiocyanates in refluxing pyridine or DMF. The second approach involves briefly heating 2-(methylcarboxy)-benzeneisothiocyanates in isopropyl alcohol with a wide variety of primary aliphatic or aromatic amines and their derivatives. Thus, most of the methods for the preparation of such compounds start with the benzene ring in place followed by construction of the pyrimidine ring. We have developed a new facile and convenient synthetic approach to 2-thioxoquinazolin-4-ones by constructing the benzene ring onto an existing pyrimidine moiety.

As a part of our synthetic strategy, 1,3-diarylthiobarbituric acids (DTBA) were used as precursors for the synthesis of various fused heterocyclic compounds. In recent years, we have reported one-pot cyclizations of DTBA with hydrazine [23,24], hydroxylamine [25], guanidine [26], etc. In addition, one-pot cyclizations of DTBA-derived arylidenes have also been reported. Recently, we reported the synthesis of fused heterocycles from ethoxymethylene derivatives of DTBA [27]. In continuation of our work on the synthesis of fused heterocycles [28,29], we herein report full details of the work and studies related to the synthesis of 2-thioxoquinazolin-4-ones from the reaction of ethoxymethylene derivatives of DTBA and active methylene compounds, such as, malononitrile and ethylcyanoacetate.

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Results and Discussion

DTBA are among the simplest synthetic intermediates and can be easily prepared in a one-pot reaction by treating 1,3-diaryl thioureas with malonic acid in the presence of acetyl chloride. DTBA undergoes condensation with ethyl orthoformate to give the condensation products, 5-ethoxymethylene-1,3-diaryl-2-thiobarbituric acids 1. These condensation products possess three electrophilic centers and can undergo cyclocondensation with various nucleophiles to give a number of fused heterocyclic systems that contain a pyrimidine ring. Thus, treatment of 1 with malononitrile in presence of NH4OAc with ZnCl2 as catalyst in refluxing acetic acid gives the corresponding 2-thioxoquinazolin-4-ones 2 in 78–85% overall yields (Scheme 1).

[1860-5397-6-120-i1]
Scheme 1: Synthesis of 2, reagents and conditions: (i) CH2(CN)2, NH4OAc/AcOH, reflux, ZnCl2 (ii) H+/H2O.

During the optimization of the cyclization of ethoxymethylene derivatives of DTBA with malononitrile, the choice of the base proved to be an important parameter. The use of NEt3 (TEA) or piperidine (in DCM or ethanol) resulted in the formation of complex mixtures (Table 1, entries 1–4). Screening at different temperatures demonstrates that some of the catalysts failed to react at room temperature (rt) and also even after heating under reflux (Table 1, entries 5–8). The reaction failed with both ZnCl2 and FeCl3 in MeOH solution at rt. Similarly, no reaction was observed with NaOCH3 and MeOH at rt. On the other hand, with NaOCH3 as base in MeOH and ZnCl2 as catalyst at rt, a relatively low yield of 2a was obtained (Table 1, entry 9). However, when this reaction was repeated in refluxing solvent the yield was increased.

Table 1: Effect of base and solvent on the yield for the synthesis of 2a.
EntryConditionsYieldc (%)
1NEt3 in DCMno product
2NEt3 in EtOHno product
3piperidine in DCMno product
4piperidine in EtOHno product
5ZnCl2 in MeOHa,bno product
6FeCl3 in MeOHa,bno product
7AlCl3 in MeOH a,bno product
8NaOCH3 in MeOHano product
9NaOCH3 in MeOHb24
10NaOCH3 in MeOH, ZnCl2b35
11NH4OAc in AcOHb67
12NH4OAc in AcOHb85

In contrast, the use of NH4OAc in refluxing acetic acid resulted in a clean cyclization to give the desired product. Dehydration and decarboxylation induced by the higher temperature and the acid produces the required quinazoline. To obtain the optimal conditions, a variety of catalysts were also investigated to detect the catalytic activities of different metal ions and acetate in the production of 2a (Table 2). It was found that NH4OAc/AcOH in ZnCl2 was the most effective (Table 2, entries 1 and 7–13); CuCl2 and HgCl2 also promoted the reactions, but the yields were poor, 22% and 12%, respectively (Table 2, entries 2 and 3). Other catalysts, including FeCl3, AlCl3 etc. failed to afford any 2a (Table 2, entries 4–6). We further found that the best yield of 2a was obtained when 5 equiv of ZnCl2 was used (Table 2, entry 13). The excessive amount of ZnCl2 for the annulation is probably due to the chelating effect of zinc ion. Thus, the NH4OAc/AcOH combination in ZnCl2 was found to be the best and gave the highest yield of 2b (85%) after refluxing for 6 h.

Table 2: Effect of catalysts in the yield for synthesis of 2aa.
EntryConditionsYieldb (%)
1ZnCl2 (1 equiv)a30
2CuCl2 (1 equiv)a22
3HgCl2 (1 equiv)a12
4FeCl3 (1 equiv)a0
5AlCl3 (1 equiv)a0
6SnCl2 (1 equiv)a0
7ZnCl2 (0.5 equiv)a18
8ZnCl2 (2 equiv)a45
9ZnCl2 (5 equiv, 2 h)a62
10ZnCl2 (5 equiv, rt, 4 h)28
11ZnCl2 (5 equiv, rt, 6 h)38
12ZnCl2 (5 equiv, 4 h)a74
13ZnCl2 (5 equiv, 6 h)a85

After optimizing the conditions, various DTBAs were used to react with malononitrile and the results are listed in Table 3. On the basis of the above noted results, a possible reaction mechanism is shown in Scheme 2. The reaction of the 5-ethoxymethylene-1,3-diaryl-2-thiobarbituric acids with malononitrile gave intermediate A, which undergoes intramolecular cyclization to form the intermediate B, and then acid hydrolysis of B afforded 2. Further evidence is that the reaction of 5-ethoxymethylene-1,3-diaryl-2-thiobarbituric acids with malononitrile under the standard conditions. This reaction only gave quinazolines and no other products were detected. In addition, this proposed mechanism was also confirmed from the literature [30,31].

Table 3: Synthesis of 7-amino-2,3-dihydro-2-thioxo-1,3-diarylquinazolin-4(1H)-onesa.
ProductRYield (%)b
2a2-CH3C6H483
2b4-ClC6H485
2c2-OCH3C6H478
[1860-5397-6-120-i2]
Scheme 2: Synthesis of 2, reagents and conditions: (i) CH2(CN)2, NH4OAc/AcOH, reflux, ZnCl2 (ii) H+/H2O.

The reaction of 5-ethoxymethylene-1,3-diaryl-2-thiobarbituric acids 1 with ethylcyanoacetate in presence of ammonium acetate and acetic acid with ZnCl2 as a catalyst afforded 7-hydroxy-2,3-dihydro-2-thioxo-1,3-diarylquinazolin-4(1H)-ones 3 in 76–87% overall yields (Scheme 3) [32,33] and these results are listed in Table 4.

[1860-5397-6-120-i3]
Scheme 3: Synthesis of 3, reagents and conditions: (i) NC-CH2-CO2Et, NH4OAc/AcOH, reflux, ZnCl2 (ii) H3O+.
Table 4: Synthesis of 7-hydroxy-2,3-dihydro-2-thioxo-1,3-diarylquinazolin-4(1H)-onesa.
ProductRYield (%)b
3a2-CH3C6H482
3b4-ClC6H487
3c2-OCH3C6H480
3dC6H576
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Conclusion

The cyclocondensation of ethoxymethylene thiobarbituric acids with active methylene compounds under the above noted catalytic system, resulted in a new method for the formation of quinazoline derivatives. Thus, the reaction of 5-ethoxymethylenepyrimidine-4,6-diones 1 with malononitrile and ethyl cyanoacetate gave 7-amino-2,3-dihydro-2-thioxo-1,3-diarylquinazolin-4(1H)-ones 2 and 7-hydroxy-2,3-dihydro-2-thioxo-1,3-diarylquinozolin-4(1H)-ones 3, respectively. This new procedure avoids the use of toxic reagents which are traditionally used for the preparation of quinazolines.

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Supporting Information

Supporting Information File 1: Experimental part.
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Supporting Information File 2: IR and NMR spectra.
Supporting Information feature copies of IR and 1H NMR spectra of 7-amino-2,3-dihydro-2-thioxo-1,3-di(2-methoxyphenyl)quinazolin-4(1H)-one (2c) and 1H and 13C NMR spectra of 7-hydroxy-2,3-dihydro-2-thioxo-1,3-di(2-methylphenyl)quinazolin-4(1H)-one (3a).
Format: PDF   Size: 436.1 KB   Download

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Acknowledgements

The authors thank SAIF, NEHU, Shillong for taking NMR spectral data.

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References

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Top
Scheme 1: Synthesis of 2, reagents and conditions: (i) CH2(CN)2, NH4OAc/AcOH, reflux, ZnCl2 (ii) H+/H2O. Move  Close
Scheme 2: Synthesis of 2, reagents and conditions: (i) CH2(CN)2, NH4OAc/AcOH, reflux, ZnCl2 (ii) H+/H2O. Move  Close
Scheme 3: Synthesis of 3, reagents and conditions: (i) NC-CH2-CO2Et, NH4OAc/AcOH, reflux, ZnCl2 (ii) H3O+. Move  Close
Table 1: Effect of base and solvent on the yield for the synthesis of 2a. Move  Close
EntryConditionsYieldc (%)
1NEt3 in DCMno product
2NEt3 in EtOHno product
3piperidine in DCMno product
4piperidine in EtOHno product
5ZnCl2 in MeOHa,bno product
6FeCl3 in MeOHa,bno product
7AlCl3 in MeOH a,bno product
8NaOCH3 in MeOHano product
9NaOCH3 in MeOHb24
10NaOCH3 in MeOH, ZnCl2b35
11NH4OAc in AcOHb67
12NH4OAc in AcOHb85
Table 2: Effect of catalysts in the yield for synthesis of 2aa. Move  Close
EntryConditionsYieldb (%)
1ZnCl2 (1 equiv)a30
2CuCl2 (1 equiv)a22
3HgCl2 (1 equiv)a12
4FeCl3 (1 equiv)a0
5AlCl3 (1 equiv)a0
6SnCl2 (1 equiv)a0
7ZnCl2 (0.5 equiv)a18
8ZnCl2 (2 equiv)a45
9ZnCl2 (5 equiv, 2 h)a62
10ZnCl2 (5 equiv, rt, 4 h)28
11ZnCl2 (5 equiv, rt, 6 h)38
12ZnCl2 (5 equiv, 4 h)a74
13ZnCl2 (5 equiv, 6 h)a85
Table 3: Synthesis of 7-amino-2,3-dihydro-2-thioxo-1,3-diarylquinazolin-4(1H)-onesa. Move  Close
ProductRYield (%)b
2a2-CH3C6H483
2b4-ClC6H485
2c2-OCH3C6H478
Table 4: Synthesis of 7-hydroxy-2,3-dihydro-2-thioxo-1,3-diarylquinazolin-4(1H)-onesa. Move  Close
ProductRYield (%)b
3a2-CH3C6H482
3b4-ClC6H487
3c2-OCH3C6H480
3dC6H576
15.Feldman, J. R.; Wagner, E. C. J. Org. Chem. 1942, 7, 31–47. doi:10.1021/jo01195a006
16.Yale, H. L. J. Heterocycl. Chem. 1977, 14, 1357–1359. doi:10.1002/jhet.5570140812
17.Mhaske, S. B.; Argade, N. P. J. Org. Chem. 2004, 69, 4563–4566. doi:10.1021/jo040153v
Go to references 15-17
18.Saeed, A.; Shaheen, U.; Bolte, M. J. Chin. Chem. Soc. 2010, 57, 82–88.
Go to reference 18
10.Li, Z.; Huang, H.; Sun, H.; Jiang, H.; Liu, H. J. Comb. Chem. 2008, 10, 484–486. doi:10.1021/cc800040z
11.Patil, Y. P.; Tambade, P. J.; Parghi, K. D.; Jayaram, R. V.; Bhanage, B. M. Catal. Lett 2009, 133, 201–208. doi:10.1007/s10562-009-0126-5
12.Couture, A.; Cornet, H.; Grandclaudon, P. Synthesis 1991, 1009–1010. doi:10.1055/s-1991-26632
13.Kotsuki, H.; Sakai, H.; Morimoto, H.; Suenaga, H. Synlett 1999, 1993–1995. doi:10.1055/s-1999-2998
Go to references 10-13
14.Abdel-Jalil, R. L.; Voelter, W.; Saeed, M. Tetrahedron Lett. 2004, 45, 3475–3476. doi:10.1016/j.tetlet.2004.03.003
Go to reference 14
6.LeMahieu, R. A.; Carson, M.; Welton, A. F.; Baruth, H. W.; Yaremko, B. J. Med. Chem. 1983, 26, 107–110. doi:10.1021/jm00355a022
7.Vandenberk, J.; Kennis, L.; Van der Aa, M.; Van Heertum, A. U.S. Patent 4, 522, 945, June 11, 1985.
8.Sohda, T.; Makino, H.; Baba, A. Eur. Patent EP0567107, Oct 27, 1993.
Go to references 6-8
9.Jiarong, L.; Xian, C.; Daxin, S.; Shuling, M.; Qing, L.; Qi, Z.; Jianhong, T. Org. Lett. 2009, 11, 1193–1196. doi:10.1021/ol900093h
Go to reference 9
3.Xia, Y.; Yang, Z.-Y.; Hour, M.-J.; Kuo, S.-C.; Xia, P.; Bastow, K. F.; Nakanishi, Y.; Nampoothiri, P.; Hackl, T.; Hamel, E.; Lee, K.-H. Bioorg. Med. Chem. Lett. 2001, 11, 1193–1196. doi:10.1016/S0960-894X(01)00190-1
Go to reference 3
4.De Clercq, E. Curr. Med. Chem. 2001, 8, 1543–1572.
5.Corbett, J. W. Curr. Med. Chem. - Anti-Infect. Agents 2002, 1, 119–140.
Go to references 4,5
1.Connolly, D. J.; Cusack, D.; O’Sullivian, T. P.; Guiry, P. J. Tetrahedron 2005, 61, 10153–10202. doi:10.1016/j.tet.2005.07.010
2.Mhaske, S. B.; Argade, N. P. Tetrahedron 2006, 62, 9787–9826. doi:10.1016/j.tet.2006.07.098
Go to references 1,2
32.Ghosh, A. K.; Bilcer, G.; Schiltz, G. Synthesis 2001, 2203–2229. doi:10.1055/s-2001-18434
33.List, B.; Castello, C. Synlett 2001, 1687–1689. doi:10.1055/s-2001-18095
Go to references 32,33
30.Green, B.; Khaidem, I. S.; Crane, R. I.; Newaz, S. S. Tetrahedron 1976, 32, 2997–3001. doi:10.1016/0040-4020(76)80158-5
31.Khaidem, I. S.; Sagolsem, L. S.; Laishram, R. S.; Khan, M. Z. R. Indian J. Chem. 1996, 35B, 911–914.
Go to references 30,31
25.Devi, N. A.; Laitonjam, W. S. Indian J. Chem. 1996, 35B, 478–479.
Go to reference 25
26.Devi, N. A.; Khuman, C. K.; Singh, R. K. T.; Laitonjam, W. S. Indian J. Heterocycl. Chem. 1998, 7, 193–196.
Go to reference 26
27.Thokchom, H. S.; Devi, N. A.; Laitonjam, W. S. Can. J. Chem. 2005, 83, 1056–1062. doi:10.1139/v05-054
Go to reference 27
28.Laitonjam, W. S.; Rajkumar, T. S.; Chingakham, B. S. Steroids 2002, 67, 203–209. doi:10.1016/S0039-128X(01)00146-5
29.Tombisana, R. K.; Laitonjam, W. S. Indian J. Chem. 1999, 38B, 847–849.
Go to references 28,29
19.Makino, S.; Suzuki, N.; Nakanishi, E.; Tsuji, T. Tetrahedron Lett. 2000, 41, 8333–8337. doi:10.1016/S0040-4039(00)01442-8
20.Makino, S.; Nakanishi, E.; Tsuji, T. Tetrahedron Lett. 2001, 42, 1749–1752. doi:10.1016/S0040-4039(01)00008-9
21.Makino, S.; Nakanishi, E.; Tsuji, T. Bull. Korean Chem. Soc. 2003, 24, 389–392. doi:10.5012/bkcs.2003.24.3.389
Go to references 19-21
22.Ivachtchenko, A. V.; Kovalenko, S. M.; Drushlyak, O. G. J. Comb. Chem. 2003, 5, 775–788. doi:10.1021/cc020097g
Go to reference 22
23.Devi, N. A.; Laitonjam, W. S. Indian J. Chem. 1994, 33B, 1091–1092.
24.Devi, N. A.; Laitonjam, W. S. Indian J. Heterocycl. Chem. 1995, 5, 139–140.
Go to references 23,24
© 2010 Moirangthem and Laitonjam; licensee Beilstein-Institut.
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