Protic ionic liquids: A lucid, rational tool for synthesis of phthalazinediones, quinoxalines and benzopyrans.

A.G. Mulik*a, D.R. Chandamb, D.R. Patilb, P. P. Patilb,G. N. Mulika, S. T. Salunkhea, M.B. Deshmukhb.

a.PG Department of Chemistry, Balwant College, Vita.415311. Maharashtra, India.

bHeterocyclic laboratory, Department of Chemistry, ShivajiUniversity, Kolhapur, 416004. Maharashtra, India.

Experimental:

General:

All chemicals were obtained from Aldrich and used as received. Progress of reaction was monitored by TLC (Silica gel 60 F254). 1H and 13C spectra of isolated compound were reported by using DMSO and CDCl3 solvent on Brucker 300MHz spectrometer with TMS as an internal standard. Elemental Analysis was carried out using EURO Elemental Analyser.

Typical procedure for the synthesis of 1H-pyrazolo[1,2-b]phthalazinediones (4a-4k) using DABCO:AcOH:H2O or 1-methylimidazole:AcOH

To a glass tube of diameter 2cm containing 0.5 g DABCO-AcOH-H2O (1/1/3 mol ratio)(Method A) or 1-methylimidazole:AcOH (1:1)(Method B) composite were added phthalhydrazide (1 mmol), malononitrile (1 mmol) and aryl aldehyde (1 mmol) at room temperature and the reaction mixture stirred magnetically for 5 minutes. After the completion of reaction monitored by TLC little water was added to the mixture entailed by filtration afforded the product with high purity without use of column chromatography which was recrystallized using ethanol and preceded for analysis.

Typical procedure for the synthesis of quinoxalines using DABCO:AcOH:H2O

To a glass tube of diameter 2cm containing 0.5 g DABCO-AcOH-H2O (1/1/3 mol ratio)composite were added 1,2-diamine (1 mmol),1,2-diketone (1 mmol) and stirred magnetically at 800Ctill completion of reaction. After the completion of reaction monitored by TLC little water was added to the mixture entailed by filtration afforded the product with high purity without use of column chromatography which was recrystallized using ethanol.

Typical procedure for the synthesis of benzopyran derivatives:

To a glass tube of diameter 2cm containing 0.5 g DABCO-AcOH-H2O (1/1/3 mol ratio)composite were added Dimedone (1 mmol),malononitrile (1 mmol) and various aromatic aldehydes (1 mmol) stirred magnetically at room temperaturetill completion of reaction. After the completion of reaction monitored by TLC little water was added to the mixture entailed by filtration afforded the product with high purity without use of column chromatography which was recrystallized using ethanol.

Spectral data of some representative Phthalazinedione derivatives:

3-Amino-1-(3-hydroxyphenyl)-4,9–dioxo-3a,4,9a–tetrahydro-1H-cyclopenta[b]naphthalene-2-carbonitrile (4i).

IR (KBr): 3372, 3268, 2192, 1660, 1578 cm-1. 1H NMR(DMSO,d6,300MHz): δ (ppm) 1.28(bs, 1H,OH), 6.00 (s,1H,CH), 6.69-7.13 (m,4H,Ar-H), 7.87(d,2H,Ar-H),8.00(bs,2H,NH2) 8.10-8.25(dd,2H,Ar-H). C13 NMR (DMSO, d6, 300MHz): δ 61.92, 63.36, 113.81, 115.88, 116.01, 117.58, 127.16, 127.70, 128.73, 128.91, 129.74, 133.78, 134.79, 150.86, 153.78, 156.76, 157.89 ppm. Anal Calcd for C18H12N4O3: C, 65.06 H, 3.64 N, 16.86%. Found: C, 65.08 H, 3.63 N, 16.85%.

3-Amino-1-(4-nitrophenyl)-4,9–dioxo-3a,4,9a–tetrahydro-1H-cyclopenta[b]naphthalene-2-carbonitrile (4g).

IR (KBr): 3433, 3323, 2197, 1659, 1601 cm-1. 1H NMR(DMSO,d6,300MHz): δ (ppm) 6.11 (s,1H,CH),7.37-7.50(dd,4H,Ar-H) 7.95 (bs,2H.NH2), 8.03-8.24(m,4H,Ar-H). C13 NMR(DMSO,d6,300MHz): δ 61.32, 63.09, 100.03, 116.68, 127.14, 129.07, 133.42, 134.22, 135.19, 138.09, 151.28, 154.18, 155.27 ppm. Anal Calcd for C18H11N5O4: C, 59.84 H, 3.07 N, 19.38%. Found: C, 59.81 H, 3.10 N, 19.34%.

3-amino-5,10-dioxo-1-(pyridin-3-yl)-5,10-dihydro-1H-pyrazolo[1,2-b]phthalazine-2-carbonitrile (4j).

IR (KBr): 3005, 2905, 2222, 1659, 1271 cm-1. 1H NMR(DMSO,d6,300MHz): δ 3.8 (s,3H,OCH3),3.89 (s,3H,OCH3), 7.1 (s,1H,CH),7.57(t,2H,Ar-H), 7.8(d,2H,Ar-H), 8.05(d,2H,Ar-H), 8.26(s,1H,Ar-H), 11.44 (bs,2H.NH2), C13 NMR(DMSO,d6,75MHz): δ 55.97, 56.32, 111.36, 111.41, 113.81, 114.60, 124.35, 125.56, 127.71, 128.20, 132.42, 149.29, 154.81, 155.79, 160 ppm. Anal Calcd for C20H16N4O4: C, 63.82; H, 4.28; N, 14.89%. Found: C, 63.85; H, 4.25; N, 14.88%.

Spectral data of some representative Quinoxaline derivatives:

2,3-diphenylquinoxaline (7a):IR (KBr): 3057, 1629, 1647, 771cm-1. 1H NMR (CDCl3, 300 MHz) δ (ppm): 7.34 (d, 6H, Ar-H), 7.37-7.55 (m, 4H, Ar-H), 7.77(q, 2H, Ar-H), 8.17 (q, 2H, Ar-H) 13C NMR (CDCl3, 300 MHz): δ 96.1, 128.1, 128.7, 129.2, 129.8, 139, 141.2, 153.3 ppm. Anal Calcd for C20H14N2: C, 85.08 H, 5.00 N, 9.92%. Found: C, 85.04 H, 5.02 N, 9.89%.

6-Nitro-2,3-diphenylquinoxaline(7c): IR (KBr): 2920, 1661, 1605, 1172cm-1. 1H NMR (CDCl3, 300 MHz) δ (ppm): 7.37-7.45(m, 6H, Ar-H), 7.57-7.60(q, 4H, Ar-H), 8.29(d, 1H, J=9.17, Ar-H), 8.55-8.59(dd, 1H, dd, J=2.50, 9.10Hz,ArH),9.09(d,J=2.38,1H).13CNMR(CDCl3,300MHz):100,123.2,125.6,128.3,129.5,129.5,129.7,129.9,130.6,138.0,138.1,140,143.5,147.9,155.4. Anal Calcd for C20H13N302: C, 73.38 H, 4.00 N, 12.84 O, 9.78%. Found: C, 73.44 H, 4.05 N, 12.92 %.

Dibenzo(a,c)phenazine(7e): IR (KBr):3059, 2923, 1605, 1499, 1357cm-1. 1H NMR (CDCl3, 300 MHz) δ (ppm): 7.71-7.88(m, 6H, Ar-H), 8.31-8.35(q, 2H, Ar-H), 8.53(t, 2H, Ar-H), 9.39(t, 2H, Ar-H). 13C NMR (CDCl3, 300 MHz): 96.15, 122.8, 126.4, 127.8, 129.6, 130.1, 130.2, 132, 142.2, 142.4 ppm. Anal Calcd for C20H12N2: C, 85.69 H, 4.31 N, 9.99 %. Found: C, 85.64 H, 4.28 N, 9.98%.

6-methyl-2,3-bis(4-methylphenyl)quinoxaline(7j): IR (KBr):3042, 2919, 1661, 1606, 1343cm-1. 1H NMR (CDCl3, 300 MHz) δ (ppm): 2.41 (s, 6H, 2CH3), 2.65 (s, 3H, CH3), 7.15(d, 4H, Ar-H), 7.29(t, 1H, Ar-H), 7.43(d, 3H, Ar-H), 7.58(q, 1H, Ar-H), 7.95(s, 1H, Ar-H), 8.04(d, 1H, Ar-H). 13C NMR (CDCl3, 300 MHz): 21.4, 21.9, 96.2, 122.8, 127.9, 128.6, 128.9, 129.6, 129.83, 129.86, 130, 132, 136, 138.4, 138.5, 139.6, 140, 141.1, 152.5, 153.1 ppm. Anal Calcd for C23H20N2: C, 85.15 H, 6.21 N, 8.63%. Found: C, 85.20 H, 6.28 N, 8.64%.

11-methyl-dibenzo(a,c)phenazine(7l): IR (KBr): 2922, 1500, 1357cm-1. 1H NMR (CDCl3, 300 MHz) δ (ppm): 2.69(s, 3H, CH3),7.67-7.81(m, 5H, Ar-H), 8.09(s, 1H, Ar-H), 8.19(d, 1H, Ar-H), 8.54(d, 2H, Ar-H), 9.36(t, 2H, Ar-H). 13C NMR (CDCl3, 300 MHz): 22, 96.1, 122.8, 126, 127.8, 128, 128.9, 129.9, 130.1, 130.4, 131.8, 132, 132.3, 140.3 ppm. Anal Calcd for C21H14N2: C, 85.69 H, 4.79 N, 9.52%. Found: C, 85.72 H, 4.82 N, 9.49%.

IR Spectrum of3-amino-1-(3-hydroxyphenyl)-5,10-dioxo-5,10-dihydro-1H-pyrazolo[1,2-b]phthalazine-2-carbonitrile.

1H Spectrum of3-amino-1-(3-hydroxyphenyl)-5,10-dioxo-5,10-dihydro-1H-pyrazolo[1,2-b]phthalazine-2-carbonitrile.

13C Spectrum of3-amino-1-(3-hydroxyphenyl)-5,10-dioxo-5,10-dihydro-1H-pyrazolo[1,2-b]phthalazine-2-carbonitrile.

IR Spectrum of3-Amino-1-(4-nitrophenyl)-4,9–dioxo-3a,4,9a–tetrahydro-1H-cyclopenta[b]naphthalene-2-carbonitrile.

1H Spectrum of3-Amino-1-(4-nitrophenyl)-4,9–dioxo-3a,4,9a–tetrahydro-1H-cyclopenta[b]naphthalene-2-carbonitrile.

13C Spectrum of3-Amino-1-(4-nitrophenyl)-4,9–dioxo-3a,4,9a–tetrahydro-1H-cyclopenta[b]naphthalene-2-carbonitrile.

IR Spectrum of 3-amino-5,10-dioxo-1-(pyridin-3-yl)-5,10-dihydro-1H-pyrazolo[1,2-b]phthalazine-2-carbonitrile

1H NMR Spectrum of 3-amino-5,10-dioxo-1-(pyridin-3-yl)-5,10-dihydro-1H-pyrazolo[1,2-b]phthalazine-2-carbonitrile

13C Spectrum of 3-amino-5,10-dioxo-1-(pyridin-3-yl)-5,10-dihydro-1H-pyrazolo[1,2-b]phthalazine-2-carbonitrile

IR Spectrum of 11-methyl-dibenzo(a,c)phenazine.

1H Spectrum of 11-methyl-dibenzo(a,c)phenazine.

13C Spectrum of 11-methyl-dibenzo(a,c)phenazine.

IR Spectrum of 2,3-diphenylquinoxaline.

1H Spectrum of 2,3-diphenylquinoxaline.

13C Spectrum of 2,3-diphenylquinoxaline.

IR Spectrum of 6-Nitro-2,3-diphenylquinoxaline.

1H Spectrum of 6-Nitro-2,3-diphenylquinoxaline.

13C Spectrum of 6-Nitro-2,3-diphenylquinoxaline.

IR Spectrum of Dibenzo(a,c)phenazine.

1H Spectrum of Dibenzo(a,c)phenazine.

13C Spectrum of Dibenzo(a,c)phenazine.

IR Spectrum of 6-methyl-2,3-bis(4-methylphenyl)quinoxaline.

1H Spectrum of 6-methyl-2,3-bis(4-methylphenyl)quinoxaline.

13C Spectrum of 6-methyl-2,3-bis(4-methylphenyl)quinoxaline.