1200L instrument. Monitoring of the reaction course and the purity of the materials was carried out
chromatographically on Silufol UV-254 plates with chloroform–methanol (10:1) and revealed using UV light
and/or iodine vapor.
1-Methyl-3-methylaminopyrrole-2,5-dione 1 was prepared according to method [14]. Absolute methanol
was distilled from CaH2.
1-Methyl-3-methylaminopyrrole-2,5-dione (1). IR spectrum, ν, cm-1: 3365 (NH), 3125, 3040, 2960,
1745 (C=O)as, 1705 (C=O)s, 1645 (C=C), 1520, 1455, 1430, 1395, 1255, 1165, 1140, 1100, 995, 810, 765.
Benzenehexacarboxylic acid trimethylimide (2). HCl (5.95 N, 2.4 ml) was added to a solution of the
pyrrole-2,5-dione 1 (2.01 g, 14.3 mmol) in aqueous methanol (80%, 24 ml), refluxed for 5 min, and cooled. The
precipitate was filtered off, washed with methanol, and dried to give the trimethylimide 2 (1.22 g, 78.3%).
Crystallization from acetic acid gave 0.67 g (43%) [mixture of acetonitrile and benzene = 0.49 g (31.4%)] of
compound 2 with mp > 350ºC (sublimes at ~ 400ºC [4]). IR spectrum, ν, cm-1: 1785, 1735 (C=O), 1655 (C=C),
1445, 1380, 1275, 1135, 1045, 960, 775, 735, 620 (1745, 1709, 1681, 1653, 1567 [5]). 1H NMR spectrum (400
MHz, DMSO-d6), δ, ppm: 3.13 (9H, s, 3CH3). 13C NMR spectrum (100 MHz, DMSO-d6), δ, ppm: 24.55
(C-13,14,15); 32.57 (C-2,3,5,8,9,12); 162.84 (C-1,4,6,7,10,11). HPLC-mass spectrum, m/z (Irel, %), peak area,
%: 327.2 [M]– (19) 100. Mass spectrum (EI, 70 eV), m/z (Irel, %): 327 [M]+ (100), 328 [M+1]+ (12.1), 270
(99.6), 187 (19.3), 185 (16.2), 101 (26.4), 100 (29.0), 71 (13.6). Found, %: C 54.94; H 2.63; N 12.90.
C15H9N3O6. Calculated, %: C 55.05; H 2.77; N 12.84.
1,1'-Dimethyl-4-methylamino[3,3']bipyrrolyl-2,5,2',5'-tetraone (3). Dry HCl (4.78 N solution in
absolute methanol, 3.7 ml) was added to a solution of maleimide 1 (2.50 g, 17.9 mmol) in absolute MeOH
(38 ml) and left for 18 h at 20ºC. The precipitate formed was filtered off, washed with absolute MeOH, and
dried to give compound 3 (2.1 g, 94.8%) with mp 166-168ºC (portion A). The filtrate was evaporated to dryness
in vacuo and the residue was triturated with a small amount of methanol. The precipitate formed was washed
with methanol and dried to give additional amount of compound 3 (40 mg, 1.8%) with mp 170-174ºC (portion
B). Portions A and B were combined and recrystallized twice from 2-propanol, to give compound 3 (1.45 g,
65.3%) with mp 172-173ºC. IR spectrum (3% solution in chloroform, cuvet diameter 0.24 mm), ν, cm-1:
3350-2900 (broad band, NH), 2960, 1745 (C=O)as, 1705 (C=O)s, 1695, 1645 (C=C), 1570, 1450, 1410, 1395,
1330, 1300, 1270, 1210, 1180, 1125, 1085, 1020, 1005, 855, 810. 1H NMR spectrum (400 MHz, CDCl3), δ, ppm
3
(J, Hz): 3.04 (3H, s, NCH3); 3.05 (3H, s, NCH3); 3.51 (3H, d, J = 5.6, NHCH3); 7.11 (1H, s, CH); 10.15 (1H,
br. s, NH). 13C NMR spectrum (100 MHz, CDCl3), δ, ppm: 23.59 (C-6'); 23.61 (C-6); 31.89 (C-7); 116.56 (C-3);
138.05 (C-3',4'); 146.68 (C-4); 164.71 (C-2'); 169.18 (C-5); 170.82 (C-5'); 173.62 (C-2). HPLC mass spectrum,
m/z (Irel, %), peak area, %: 248.1 [M-H]+ (80), 234.2 [M-Me]+ (50) (100). Mass spectrum (EI, 70 eV), m/z (Irel,
%): 249 [M]+ (100), 250 [M+1]+ (12.9), 164 (37.7), 163 (19.8), 162 (34.1), 106 (19.1), 79 (58.0), 78 (16.2), 64
(15.5). Found, %: C 52.85; H 4.37; N 16.92 C11H11N3O4. Calculated, %: C 53.01; H 4.45; N 16.86.
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