Scientia Iranica C (2013) 20 (3), 555–560

Sharif University of Technology

Scientia IranicaTransactions C: Chemistry and Chemical Engineering

www.sciencedirect.com

Ionic liquid [bmim][NO3], an efficient medium for green and one-potsynthesis of benzothiazinones at room-temperatureA. Sharifi ∗, M.S. Abaee, M. Rouzgard, M. MirzaeiChemistry and Chemical Engineering Research Center of Iran, Tehran, P.O. Box 14335-186, Iran

Received 17 June 2012; revised 12 November 2012; accepted 16 December 2012

KEYWORDSBenzothiazin-3-ones;Green chemistry;Ionic liquids;Heterocycles.

Abstract A one-pot room-temperature procedure is developed for an efficient reaction of 2-aminothiophenols with 2-bromoalkanoates in ionic liquid [bmim][NO3] to obtain high yields of differentbenzothiazin-3-ones under base- and additive-free conditions. Products are easily separated from thereactionmixtures by Et2O extraction. Notably, condensation of the extract under reduced pressure resultsin precipitation of the products and, consequently, no chromatographic separation is needed. The ionicliquid can be recovered and successfully recycled into subsequent reactions without significant loss ofactivity.

© 2013 Sharif University of Technology. Production and hosting by Elsevier B.V. All rights reserved.

1. Introduction

There is a world-wide demand in the new millennium formore severe environmental enforcements to lower or eliminatethe use of toxic reagents and solvents. In this connection, IonicLiquids (ILs) have emerged as green and reusable solvents indifferent areas of chemistry [1–3]. Notably, ILs can be tailoredtomeet particular physical and chemical demands, and increasethe selectivity and reactivity of various transformations [4–7].This feature is of great importance in today’s synthetic organicchemistry, and, therefore, IL’s are, nowadays, among verypromising benign surrogates for classic organic solvents. Inaddition, IL’s are recoverable in many instances, have very lowvapor pressure and high thermal stability, can dissolve manyorganic reactants, and have relatively long shelf lives [8–10].

Structures of type 3, which represent the 2H-benzo[b][1,4]thiazin-3(4H)-one moiety, are considered as important hete-rocycles, due to featuring biological [11,12], medicinal [13,14],and agricultural [15] characteristics. Therefore, these com-pounds have been the target of extensive synthetic studies. One

∗ Corresponding author. Tel.: +98 21 44580749; fax: +98 21 44580785.E-mail address: sharifi@ccerci.ac.ir (A. Sharifi).

Peer review under responsibility of Sharif University of Technology.

1026-3098© 2013 Sharif University of Technology. Production and hosting by Els

http://dx.doi.org/10.1016/j.scient.2012.12.038

approach involves a stepwise substitution-reduction procedureconsisting of the addition of thiol acetate to halonitrobenzenes,plus the reduction of the nitro moiety, and then a cyclizationstep [16,17]. Other methods are:

(1) Cyclization of o-aminothiophenols or their disulfide equiv-alents with α-substituted carbonyl compounds [18–21];

(2) Substitution of chlorine in 2-chloroanilines with Na2Sto give an aminothiophenol intermediate, which furtherannulates with chloroacetic acid derivatives [22];

(3) Combination of 2-chlorothiophenols with chloroacetylchlorides and amines in one-pot [23,24];

(4) Ring enlargement of smaller heterocycles into a benzoth-iazinone structure [25,26].

However, there is still a need for more convenient andefficient methods for the synthesis of 3, since many of the re-ported procedures are carried out in a step-wise fashion, re-quire elevated temperatures, involve uncommercially availablereagents, and are low yielding.

In the framework of our studies on heterocyclic systems[27–29], and in continuation of our previous research on the de-velopment of environmentally benign methodologies [30,31],we would like to report a base-free [bmim][NO3] mediated an-nulation of 2-aminothiophenolswith 2-bromoalkanoates, usingno other additive (Scheme 1). The present one-pot work em-ploys mild conditions and involves a broad range of reactants.In addition, reactions take place at ambient temperature andthe IL can be reused efficiently in subsequent reactions.

evier B.V. All rights reserved.

556 A. Sharifi et al. / Scientia Iranica, Transactions C: Chemistry and Chemical Engineering 20 (2013) 555–560

Scheme 1: IL mediated synthesis of various benzothiazinones.

2. Experimental

2.1. General

Progress of the reactions was monitored by TLC using silicagel coated plates and EtOAc/hexane solutions as the eluent.Melting points are uncorrected. FT-IR spectra were recordedusing KBr disks on a Bruker Vector-22 infrared spectrometerwith absorptions being reported as wave numbers (cm−1).1H NMR (500 MHz) and 13C NMR (125 MHz) spectra wereobtained on a FT-NMR Bruker Ultra ShieldTM instrument asCDCl3 solutions, and the chemical shifts are expressed as δunits with Me4Si as the internal standard. Mass spectra wererecorded on a Finnigan Mat 8430 apparatus at ionizationpotential of 70 eV. Elemental analyses were done by a ThermoFinnigan Flash EA 1112 instrument. [Bmim][NO3] was preparedusing available procedures [32] and recovered by removing itsvolatiles under reduced pressure at 50 °C for 1 h. Reagents werepurchased from commercial sources and were freshly usedafter being purified by standard procedures. The identity of theknown productswas confirmed by comparison of their physicaland spectroscopic datawith those reported. Newproductswerecharacterized by 1H NMR, 13C NMR, IR and mass spectrometry,and their purity was confirmed by elemental analyses.

2.2. Typical procedure

A mixture of 1 (1 m mol) and 2 (1 m mol) in [bmim][NO3](1 m mol) was stirred in a flask at room-temperature for 1 h.After reactions were completed (based on TLC monitoring), thereaction mixture was extracted with Et2O. The etheral phasewas washed with brine, dried over anhydrous Na2SO4, andconcentrated under reduced pressure to obtain product 3. Theproduct was purified by recrystallization from ether. The ILwas recovered by evaporating its volatile content and reusedin subsequent reactions.

2.3. Spectral data of new products

6-Chloro-2-ethyl-2H -benzo[b][1,4] thiazin-3(4H)-one(3dd). White solid: mp 140–142 ˚C; 1H NMR (500 MHz, CDCl3)δ9.58 (br s, NH), 7.26 (d, J = 8.0 Hz, 1H), 7.02 (d, J = 2.0 Hz, 1H),6.99 (dd, J = 8.5, 2.0 Hz, 1H), 3.35 (dd, J = 8.5, 6.0 Hz, 1H),1.98-1.94 (m, 1H), 1.67-1.64 (m, 1H), 1.10 (t, J = 7.5 Hz, 3H);13C NMR (125 MHz, CDCl3) δ 168.9, 137.4, 133.0, 129.6, 124.2,117.4, 117.3, 44.6, 23.6, 11.7; IR (KBr) 3188, 2964, 1855, 1664,1465, 1097, 866, 740 cm−1; MS 227, 198, 170, 134, 95, 69, 39,27; Elemental analyses calcd for C10H10ClNOS: %C, 52.75; %H,4.43; %N, 6.15; %S, 14.08. Found: %C, 52.77; %H, 4.48; %N, 6.10%;%S, 14.00.

6-Chloro-2-propyl-2H-benzo[b][1,4] thiazin-3(4H)-one(3de). White solid: mp 129–131 ˚C; 1H NMR (500 MHz, CDCl3)δ9.35 (br s, NH), 7.26 (d, J = 8.5 Hz, 1H), 7.02 (dd, J = 8.0, 2.0 Hz,1H), 6.96 (d, J = 2.0 Hz, 1H), 3.44 (dd, J = 8.5, 6.0 Hz, 1H), 2.08-1.89 (m, 1H), 1.64-1.62 (m, 2H), 1.61-1.59 (m, 1H), 0.96 (t, J =

7.0 Hz, 3H); 13C NMR (125 MHz, CDCl3) δ 168.9, 137.3, 133.0,129.6, 124.3, 117.5, 117.2; 42.6, 32.1, 20.3, 13.8; IR (KBr) 3194,2956, 1853, 1666, 1469, 1228, 800, 673, 540 cm−1; MS 241,154, 138, 114, 59; Elemental analyses calcd for C11H12ClNOS:%C, 54.65; %H, 5.00; %N, 5.79; %S, 13.26. Found: %C, 54.36; %H,4.97; %N, 5.33%; %S, 13.22.

6-Chloro-2-(2-hydroxyethyl)-2H-benzo[b][1,4]thiazin-3(4H)-one (3df).White solid:mp 132–133 ˚C; 1HNMR (500MHz,CDCl3)δ 10.11 (br s, NH), 7.07 (d, J = 8.5 Hz, 1H), 6.88 (d, J =

2.0 Hz, 1H), 6.80 (dd, J = 8.5, 2.0 Hz, 1H), 3.65-3.56 (m, 2H),3.50 (t, J = 6.0 Hz, 1H), 1.96 (br s, OH), 2.03-1.96 (m, 1H), 1.66-1.59 (m, 1H); 13C NMR (125 MHz, CDCl3) δ 168.1, 138.2, 132.6,129.2, 123.4, 117.3, 117.2, 58.9, 39.4, 32.8; IR (KBr) 3194, 2954,2364, 1668, 1471, 800 cm−1; MS 243, 212, 170, 116, 95, 69, 55,43, 31; Elemental analyses calcd for C10H10ClNO2S: %C, 49.28;%H, 4.14; %N, 5.75; %S, 13.16. Found: %C, 49.16; %H, 4.17; %N,5.46%; %S, 13.14.

7-Fluoro-2-(2-hydroxyethyl)-2H-benzo[b] [1,4]thiazin-3(4H)-one (3ef). White solid: mp 110–111 ˚C; 1H NMR (500MHz, CDCl3) δ 9.93 (br s, NH), 6.91 (dd, J = 8.3, 2.7 Hz, 1H),6.85 (dd, J = 8.8, 5.0 Hz, 1H), 6.90 (ddd, J = 8.8, 8.2, 2.7 Hz,1H), 3.70-3.61 (m, 2H), 3.55 (dd, J = 8.2, 6.4 Hz, 1H), 3.27 (br s,OH), 2.08-2.01 (m, 1H), 1.72-1.66 (m, 1H); 13C NMR (125 MHz,CDCl3) δ 168.0, 159.6, 157.6, 133.4, 132.8, 120.6, 120.5, 118.5,118.5, 115.0, 114.8, 114.3, 114.1, 59.1, 39.5, 32.9; IR (KBr) 3188,2877, 1859, 1654, 1489, 808, 605 cm−1; MS 227, 209, 168, 154,83, 69, 29; Elemental analyses calcd for C10H10FNO2S: %C, 52.85;%H, 4.44; %N, 6.16; %S, 14.11. Found: %C, 52.54; %H, 4.83; %N,6.34%; %S, 14.01.

Ethyl 7-methoxy-3-oxo-3,4-dihydro-2H -benzo[b][1,4]thiazine-2-carboxylate (3cg). White solid: mp 138–139 ˚C; 1HNMR (500 MHz, CDCl3) δ 10.03 (br s, NH), 6.85 (d, J = 8.7 Hz,1H), 6.73 (d, J = 2.7 Hz, 1H), 6.63 (dd, J = 8.7, 2.7 Hz, 1H), 4.12-4.07 (m, 1H), 4.07 (s, 1H), 4.05-4.00 (m, 1H), 3.67 (s, 3H), 1.08(t, 7.1 Hz, 3H); 13C NMR (125MHz, CDCl3) δ 167.3, 162.6, 155.9,130.6, 118.7, 118.0, 114.1, 112.7, 62.6, 55.9, 45.6, 14.2; IR (KBr)3184, 2951, 1730, 1676, 1492, 1282, 866, 812, 628 cm−1; MS267, 194, 166, 123, 96, 69, 45, 29; Elemental analyses calcd forC12H13NO4S: %C, 53.92; %H, 4.90; %N, 5.24; %S, 12.00. Found: %C,53.62; %H, 4.85; %N, 4.84%; %S, 12.12.

Ethyl 7-methoxy-2-methyl-3-oxo-3,4-dihydro-2H -benzo[b][1,4]thiazine-2-carboxylate (3ch). White solid: mp 127–128 ˚C; 1H NMR (500 MHz, CDCl3) δ 8.52 (br s, NH), 6.86 (d, J =

2.6 Hz, 1H), 6.84 (d, J = 8.7 Hz, 1H), 6.78 (dd, J = 8.7, 2.7 Hz,1H), 4.19-4.12 ((m, 1H), 4.10-4.03 (m, 1H), 3.80 (s, 3H), 1.82 (s,3H), 1.07 (t, J = 7.1 Hz, 3H); 13C NMR (125MHz, CDCl3) δ 170.0,166.5, 156.25, 130.4, 120.2, 118.0, 114.4, 112.6, 62.7, 56.0, 50.5,19.7, 14.2; IR (KBr) 3192, 2964, 1735, 1668, 1494, 1222, 815,615 cm−1; MS 281, 209, 181, 166, 138, 96, 84, 60, 30; Elementalanalyses calcd for C13H15NO4S: %C, 55.50; %H, 5.37; %N, 4.98;%S, 11.40. Found: %C, 55.56; %H, 5.45; %N, 4.95%; %S, 11.31.

Ethyl 2-ethyl-7-methoxy-3-oxo-3,4-dihydro-2H -benzo[b][1,4]thiazine-2-carboxylate (3ci).White solid:mp 102–103˚C; 1H NMR (500 MHz, CDCl3) δ 9.03 (br s, NH), 6.89 (d, J =

2.6 Hz, 1H), 6.85 (d, J = 8.7 Hz, 1H), 6.78 (dd, J = 8.7, 2.7 Hz,1H), 4.20-4.15 (m, 1H), 4.14-4.08 (m, 1H), 3.80 (s, 3H), 2.30-2.20(m, 2H), 1.16 (t, J = 7.3 Hz, 3H), 1.11 (t, J = 7.0 Hz, 3H); 13CNMR (125MHz, CDCl3) δ 169.3, 166.2, 156.2, 130.0, 120.3, 118.1,114.3, 112.8, 62.7, 56.8, 56.0, 26.1, 14.3, 9.9; IR (KBr) 3186, 2968,

A. Sharifi et al. / Scientia Iranica, Transactions C: Chemistry and Chemical Engineering 20 (2013) 555–560 557

Table 1: [Bmim][NO3] mediated synthesis of 3.

Entry Reactants Product Time (h) Yield%a

1 1a+2a 2 83

2 1a+2b 2 88

3 1a+2c 24 92

4 1b+2b 0.5 93

5 1c+2a 0.25 89

6 1d+2d 2 92

7 1d+2e 4 90

8 1a+2f 1 90

9 1d+2f 2 85

10 1e+2f 3 82

11 1a+2g 1 92

12 1a+2h 1 90

13 1c+2g 3 88

(continued on next page)

558 A. Sharifi et al. / Scientia Iranica, Transactions C: Chemistry and Chemical Engineering 20 (2013) 555–560

Table 1 (continued)

Entry Reactants Product Time (h) Yield%a

14 1c+2h 3 88

15 1c+2i 3 90

16 1f+2g 1 91

17 1f+2i 1 88

a Isolated yields.

1724, 1494, 1247, 825, 655 cm−1; MS 295, 22, 194, 166, 136, 80,69, 29; Elemental analyses calcd for C14H17NO4S: %C, 56.93; %H,5.80; %N, 4.74; %S, 10.86. Found: %C, 56.57; %H, 5.65; %N, 4.74%;%S, 11.01.

Ethyl 7-chloro-3-oxo-3,4-dihydro-2H -benzo[b][1,4] thia-zine-2-carboxylate (3fg). White solid: mp 152–153 ˚C; 1HNMR(500 MHz, CDCl3) δ 8.94 (br s, NH), 7.35 (d, J = 2.2 Hz, 1H),7.20 (dd, J = 8.5, 2.2 Hz, 1H), 6.87 (d, J = 8.5 Hz, 1H), 4.24 (s,1H), 4.24-4.14 (m, 2H), 1.18 (t, 7.1 Hz, 3H); 13C NMR (125 MHz,CDCl3) δ 166.7, 163.5, 134.8, 129.6, 128.2, 127.9, 119.0, 118.4,66.2, 45.0, 15.7; IR (KBr) 3473, 3188, 2947, 1749, 1676, 1240,821 cm−1; MS 271, 198, 170, 135, 108, 95, 69, 45, 29; Elementalanalyses calcd for C11H10ClNO3S: %C, 48.62; %H, 3.71; %N, 5.15;%S, 11.80. Found: %C, 48.37; %H, 3.48; %N, 5.38%; %S, 12.05.

Ethyl 7-chloro-2-ethyl-3-oxo-3,4-dihydro-2H -benzo[b][1,4]thiazine-2-carboxylate (3fi).White solid: mp 105–107 ˚C;1H NMR (500 MHz, CDCl3) δ 8.98 (br s, NH), 7.35 (d, J = 2.2 Hz,1H), 7.18 (dd, J = 8.5, 2.2 Hz, 1H), 6.85 (d, J = 8.5 Hz, 1H), 4.20-4.11 (m, 2H), 2.30-2.20 (m, 2H), 1.16 (t, J = 7.3 Hz, 3H), 1.12(t, J = 7.1 Hz, 3H); 13C NMR (125 MHz, CDCl3) δ 168.9, 166.2,134.9, 129.2, 128.0, 127.8, 120.9, 118.0, 62.9, 56.4, 26.1, 14.2,9.8; IR (KBr) 3190, 2960, 1726, 1477, 1363, 1228, 823, 547 cm−1;MS 299, 198, 170, 95, 69, 45, 29; Elemental analyses calcd forC13H14ClNO3S: %C, 52.09; %H, 4.71; %N, 4.67; %S, 10.70. Found:%C, 52.17; %H, 4.58; %N, 4.88%; %S, 10.99.

3. Results and discussion

First, the conditionswere optimized using the unsubstitutedparent reactants, 1a and 2a, in ionic liquid [bmim][NO3](Table 1). The best results were obtained when the reactantswere mixed in the IL at room-temperature, giving 83% of3aa after 2 h (entry 1). With no IL, no product was obtainedafter a long reaction time, illustrating the promoting effectof the IL in the catalysis of the reaction. Under optimumconditions, the same reactions of 1a with 2b and 2c gave highyields of the respective products within 2–24 h (entries 2–3).Electron releasing- (entries 4–5) and electron withdrawingsubstituted thiophenols (entries 6–7) also annulated with 2-bromoalkanoates to provide high yields of products, 3bb–3de,

Figure 1: Efficient recovery of the catalyst.

in relatively short time periods. Reactions of 1 with lactone2f also proceeded efficiently to produce 2-hydroxyethylsubstituted products (entries 8–10). To further illustrate thegenerality of themethod,we applied optimumconditions to thereactions of1with 2-bromo-2-alkylmalonates2g–i. Thiophenol1a rapidly reacted with 2g–h to produce 3ag–3ah 90%–92%(entries 11–12). In the same manner, 1c and 1f gave highyields of their respective products when they were subjectedto reaction conditions (entries 13–17).

It is noteworthy that all reactions take place in one potand at room temperature within short time periods, andproducts are obtained by a simple ethereal extraction. In themajority of cases, concentration of the ethereal phase at lowpressure resulted in precipitation of the products, allowing aneasy purification by recrystallization from ether and avoidingcolumn chromatography separation. As a result of this, theIL was recovered and reused in subsequent reactions withoutsignificant loss of activity. This is shown for five reactions of 1awith 2a, in a row, in Figure 1.

Based on these results, a mechanism can be offered for theprocedure, as shown in Figure 2. Initially, removal of the protonof 2-aminothiophenol 1 by nitrate anion leads to the formationof the thiophenolate moiety. The thiophenolate then attacks 2to produce the intermediate 12. On the other hand, the IL itself

A. Sharifi et al. / Scientia Iranica, Transactions C: Chemistry and Chemical Engineering 20 (2013) 555–560 559

Figure 2: The proposed mechanism.

as a polar medium helps the process by easing the dissociationof the acidic proton of the thiol group and also by coordinationto the carbonyl group of the intermediate to facilitate the final insitu annulation. Similar mechanisms are offered for some otherIL mediated reactions [33,34].

4. Conclusion

This procedure presents a very convenient route to differ-ent benzothiazin-3-ones derivatives, because the cyclizationtakes place in one-pot, starting from 2-aminothiophenols and2-bromoalkanotes with different steric and electronic charac-teristics. Moreover, the reaction proceeds chemoselectively atroom temperature, giving high yields of the products in shorttime periods, and the IL is efficiently recyclable.

Acknowledgments

Authors would like to thank the Iran National ScienceFoundation (INSF) for financial support of this work (Project88000118).

References

[1] Wasserscheid, P. and Welton, T., Ionic Liquids in Synthesis, Wiley-VCH,Weinheim (2002).

[2] Hallett, J.P. and Welton, T. ‘‘Room-temperature ionic liquids: solvents forsynthesis and catalysis 2’’, Chem. Rev., 111, pp. 3508–3576 (2011).

[3] Martins, M.A.P., Frizzo, C.P., Moreira, D.N., Zanatta, N. and Bonacorso, H.G.‘‘Ionic liquids in heterocyclic synthesis’’, Chem. Rev, 108, pp. 2015–2050(2008).

[4] Zare, A., Hasaninejad, A., Salimi Beni, A., Moosavi-Zared, A.R., Merajod-dina, M., Kamali, E., Akbari-Seddigh, M. and Parsaee, Z. ‘‘Ionic liquid1-butyl-3-methylimidazolium bromide ([Bmim]Br) as a green and neu-tral reaction media for the catalyst-free synthesis of 1-amidoalkyl-2-naphthols’’, Sci. Iran, 18, pp. 433–438 (2011).

[5] Hardacre, C., Holbrey, J., Nieuwenhuyzen,M. and Youngs, T.G.A. ‘‘Structureand solvation in ionic liquids’’, Acc. Chem. Res., 40, pp. 1146–1155 (2007).

[6] Pârvulescu, V.I. and Hardacre, C. ‘‘Catalysis in ionic liquids’’, Chem. Rev.,107, pp. 2615–2665 (2007).

[7] Chauhan, S.M.S., Agarwal, S. and Kumari, P. ‘‘Synthesis of metal-freephthalocyanines in functionalized ammonium ionic liquids’’, Synth.Commun, 17, pp. 2917–2925 (2007).

[8] Earle, M.J., McCormac, P.B. and Seddon, K.R. ‘‘Diels–Alder reactions in ionicLiquids, A safe recyclable alternative to lithium perchlorate–diethyl ethermixtures’’, Green Chem., 1, pp. 23–25 (1999).

[9] Huddleston, J.G.,Willauer, H.D., Swatloski, R.P., Visser, A.E. and Rogers, R.D.‘‘Room temperature ionic liquids as novel media for clean liquid–liquidextraction’’, Chem. Commun, pp. 1765–1766 (1998).

[10] Wilkes, J.S. ‘‘A short history of ionic liquids—from molten salts to neotericsolvents’’, Green Chem., 4, pp. 73–80 (2002).

[11] Marchetti, C., Ulisse, S., Bruscoli, S., Russo, F.P., Migliorati, G., Schiaffella, F.,Cifone, M.G., Riccardi, C. and Fringuelli, R. ‘‘Induction of apoptosis by 1,4-benzothiazine analogs in mouse thymocytes’’, J. Pharmacol. Exp. Ther, 300,pp. 1053–1062 (2002).

[12] Fringuelli, R., Schiaffella, F., Navarro, M.P.U., Milanese, L., Santini, C.,Rapucci, M., Marchetti, C. and Riccardi, C. ‘‘1,4-Benzothiazine analoguesand apoptosis: structure–activity relationship’’, Bioorg. Med. Chem., 11,pp. 3245–3254 (2003).

[13] Cecchetti, V., Schiaffella, F., Tabarrini, O. and Fravolini, A. ‘‘(1,4-Benzothiazinyloxy)alkylpiperazine derivatives as potential antihy-pertensive agents’’, Bioorg. Med. Chem. Lett., 10, pp. 465–468 (2000).

[14] Fujita, M., Ito, S., Ota, A., Kato, N., Yamamoto, K., Kawashima, Y.,Yamauchi, H. and Iwao, J. ‘‘Synthesis and calcium ion antagonistic activ-ity of 2-[2-[(aminoalkyl)oxy]-5-methoxyphenyl]-3,4-dihydro-4-methyl-3-oxo-2H-1,4-benzothiazines’’, J. Med. Chem., 33, pp. 1898–1905 (1990).

[15] Anderson, J.E., Bell, S., Best,W.M., Drygala, P.F. andWatson, K.G. ‘‘Synthesisand herbicidal activity of 1,4-benzoxazin-3-one sulfonylureas’’, Pestic. Sci.,46, pp. 131–138 (1996).

[16] Cecchetti, V., Fravolini, A., Fringuelli, R., Mascellani, G., Pagella, P., Palmi-oli, M., Segre, G. and Terni, P. ‘‘Quinolonecarboxylic acids. 2. Synthe-sis and antibacterial evaluation of 7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de][1,4]benzothiazine-6-carboxylic acids’’, J. Med. Chem., 30, pp. 465–473(1987).

[17] Molteni, V., He, X., Nabakka, J., Yang, K., Kreusch, A., Gordon, P.,Bursulaya, B., Warner, I., Shin, T., Biorac, T., Ryder, N.S., Goldberg, R.,Doughty, J. and He, Y. ‘‘Identification of novel potent bicyclic peptidedeformylase inhibitors’’, Bioorg. Med. Chem. Lett., 14, pp. 1477–1481(2004).

[18] Cizej, V.L. and Urleb, U. ‘‘The synthesis of 3,4-dihydro-2-methyl-3-oxo-2H-benzo-1,4-thiazine-2-carboxylic acids’’, J. Hetrocyclic Chem., 33,pp. 97–101 (1996).

[19] Shawali, A.S., Elsheikh, S. and Párkányi, C. ‘‘Cyclization of thiohydrazonateesters and azo-hydrazone tautomerism of 2-arylhydrazono-3-oxo-1,4-benzothiazines’’, J. Heterocyclic Chem., 40, pp. 207–212 (2003).

[20] Dolzhenko, A.V. and Chui, W.-K. ‘‘A synthesis of a novel hetero-cyclic system: 2H-furo[3,2-b][1,4]benzothiazin-2-one’’, Heterocycles, 63,pp. 2623–2626 (2004).

[21] Fujita, M., Ota, A., Ito, S., Yamamoto, K. and Kawashima, Y. ‘‘A novel, conve-nient synthesis of 2-aryl-3-oxo-3,4-dihydro-2H-1,4-benzothiazines’’, Syn-thesis, pp. 599–604 (1988).

[22] Guarda, V.L.deM., Perrissin, M., Thomasson, F., Ximenes, E.A., Galdino, S.L.,Pitta, I.R. and Luu-Duc, C. ‘‘Synthesis and microbiological activity ofsome 4-butyl-2H-benzo[1,4]thiazin-3-one derivatives’’, Il Farmaco, 56,pp. 689–693 (2001).

[23] Gupta, R.R., Ojha, K.G. and Kumar, M. ‘‘Studies on phenothiazines. Part7. Synthesis of 3-substituted 2-aminobenzenethiols and their conversioninto phenothiazines’’, J. Heterocyclic Chem., 17, pp. 1325–1327 (1980).

[24] Zuo, H., Li, Z.-B., Ren, F.-K., Falck, J.R., Lijuan, M., Ahn, C. and Shin, D.-S. ‘‘Microwave-assisted one-pot synthesis of benzo[b][1,4]thiazin-3(4H)-ones via Smiles rearrangement’’, Tetrahedron, 64, pp. 9669–9674 (2008).

[25] Shimizu, H., Ueda, N., Kataoka, T. and Hori, M. ‘‘Non-stereospecific ringexpansion reactions of benzothiazoline sulfoxides’’, Chem. Pharm. Bull., 32,pp. 2571–2590 (1984).

[26] Hori, M., Kataoka, T., Shimizu, H. and Imai, Y. ‘‘Studies on benzothiazolinederivatives. III. Reactions of 2,2-disubstituted benzothiazolines withhaloacyl halides or acid anhydrides’’, Chem. Pharm. Bull., 27, pp. 1973–1981(1979).

[27] Sharifi, A., Abaee,M.S., Tavakkoli, A.,Mirzaei,M. and Zolfaghari, A.R. ‘‘Facilemontmorillonite K-10 supported synthesis of xanthene derivatives undermicrowave and thermal conditions’’, Synth. Commun., 38, pp. 2958–2966(2008).

[28] Abaee, M.S., Hamidi, V. and Mojtahedi, M.M. ‘‘Ultrasound promotedaminolysis of epoxides in aqueous media: a rapid procedure with nopH adjustment for additive-free synthesis of β-aminoalcohols’’, Ultrason.Sonochem., 15, pp. 823–827 (2008).

[29] Abaee, M.S., Mojtahedi, M.M., Pasha, G.F., Akbarzadeh, E., Shock-ravi, A., Mesbah, A.W. and Massa, W. ‘‘Switching the reactivity ofdihydrothiopyran-4-one with aldehydes by aqueous organocatalysis:Baylis–Hillman, aldol, or aldol condensation reactions’’, Org. Lett., 13,pp. 5282–5285 (2011).

[30] Sharifi, A., Barazandeh, M., Abaee, M.S. and Mirzaei, M. ‘‘Omim][BF4], agreen and recyclable ionic liquid medium for the one-pot chemoselectivesynthesis of benzoxazinones’’, Tetrahedron Lett., 51, pp. 1852–1855 (2010).

[31] Sharifi, A., Barazandeh, M., Abaee, M.S. and Mirzaei, M. ‘‘K2CO3/H2O in[Omim][BF4] ionic liquid: a greenmedium for efficient room-temperaturesynthesis of N-substituted 1,4-benzoxazin-3-ones’’, J. Heterocyclic Chem.,49, pp. 933–938 (2012).

[32] Dinares, I., de Miguel, C.G., Ibanez, A., Mesquida, N. and Alcalde, E.‘‘Imidazolium ionic liquids: A simple anion exchange protocol’’, GreenChem., 11, pp. 1507–1510 (2009).

560 A. Sharifi et al. / Scientia Iranica, Transactions C: Chemistry and Chemical Engineering 20 (2013) 555–560

[33] Zare, A., Parhami, A., Moosavi-Zare, A.R., Hasaninejad, A., Khalafi-Nezhad, A. and Beyzavi, M.H. ‘‘A catalyst-free protocol for the green andefficient condensation of indoles with aldehydes in ionic liquids’’, Can. J.Chem., 87, pp. 416–421 (2009).

[34] Hasaninejad, A., Zare, A., Shekouhy, M. and Ameri Rad, J. ‘‘Catalyst-free one-pot four component synthesis of polysubstituted imidazolesin neutral ionic liquid 1-butyl-3-methylimidazolium bromide’’, J. Comb.Chem., 12, pp. 844–849 (2010).

Ali Sharifi obtained his B.S. and M.S. degrees from Shiraz University, Iran, andthen obtained his Ph.D. degree from Sharif University of Technology, includinga six-month research project at the Institute of Organic Chemistry of Justus-LiebigUniversity, Giessen, Germany, in 1995. He is currently Associate Professorin the Faculty of Organic Chemistry and Natural Products at the Chemistryand Chemical Engineering Research center of Iran (CCERCI). His researchinterests include: newmethodologies in organic synthesis, green chemistry andmedicinal chemistry.

M. Saeed Abaee obtained his M.S. degree from the University of Tehran, Iran,and a Ph.D. degree from the University of Saskatchewan, Canada, in 1999.He is currently Associate Professor in the Faculty of Organic Chemistry andNatural Products at the Chemistry and Chemical Engineering Research center ofIran (CCERCI). His research interests include: the study of Lewis acid catalyzedreactions, thiopyran heterocycles, and environmental chemistry.

Mahdiyeh Rouzgard obtained her B.S. degree from Kharazmi University, Iran,in 2006, and then entered the Chemistry and Chemical Engineering Researchcenter of Iran (CCERCI), in 2008, to study for her MS degree. Her researchinterests include: ionic liquid mediated organic synthesis.

MojtabaMirzaei obtained his BS degree fromTabriz University, in 1997, and hisM.S. degree from the Chemistry and Chemical Engineering Research center ofIran (CCERCI). He is currently a Ph.D. degree student at the University of Tehran,Iran.