N CO2Me CO2Me CO2Me 1 N N X RO2C C C CO2R a b c d X = H X = Me X = Cl X = NO2 2 a b R = Me R = Et 3 N N CO2R CO2R CO2R CO2R CO2R CO2R X a b c d e X = H, R = Me X = H, R = Et X = Me, R = Me X = Cl, R = Me X = NO2, R = Me 4 1 2 3 4 5 6 212 J. CHEM. RESEARCH (S), 1997 J. Chem. Research (S), 1997, 212–213† Reaction between 1,10-Phenanthroline and Dialkyl Acetylenedicarboxylates. A Facile Synthetic Route to Helical Dipyrrolophenanthrolines† Issa Yavari,* Malek Taher Maghsoodlou and Ali Pourmossavi Chemistry Department, Tarbiat Modarres University, P.O.Box 14155-4838, Tehran, Iran 1,10-Phenanthroline and its 5-substituted derivatives react with dialkyl acetylenedicarboxylates to give dipyrrolo[1,2- a:2p,1p-k][1,10]phenanthroline derivatives, which exhibit nonplanarity enforced by the crowding of the ester groups. Many diverse products can be prepared from the addition of acetylenic esters to nitrogen-containing heterocycles.1 An example is the interesting reaction between pyridine and dimethyl acetylenedicarboxylate in methanol, in which the indolizine-1,2,3-tricarboxylate (1) is isolated.2–5 However, there appears to be no report of a reaction product formed from 1,10-phenanthroline (2a)6 and acetylenic esters.We have found that 1,10-phenanthrolines 2a–d undergo reaction with dialkyl acetylenedicarboxylates 3a,b to give hitherto unknown dipyrrolo[1,2-a:2p,1p-k][1,10]phenanthroline derivatives 4a–e in moderate yields. The essential structures of compounds 4a–e were deduced from their elemental analyses and their 1H and 13C NMR spectra as well as from the IR spectra which exhibited strong C�O signals.The mass spectra of these compounds displayed molecular ion peaks at m/z 604, 688, 618, 638 and 649 for 4a–e, respectively. Initial fragmentations involve loss of the side chains. The 1H NMR spectrum of 4a exhibited three single sharp lines at d 3.37, 3.99 and 4.03, readily recognizable as arising from methoxy protons, along with two superimposed AB systems and an A2 system for the 1,10-phenanthroline residue in 4a.The 13C NMR spectrum of 4a displayed three signals for the methoxy (d 51.48, 51.95 and 52.78) groups, along with nine signals for the dipyrrolophenanthroline nucleus. The chemical shifts of the ester carbonyl groups at d 158.16, 163.64 and 166.26 are consistent with the symmetrical structure of 4a. The 1H NMR spectrum of compound 4b is analogous to that obtained for 4a, except for the ester groups which exhibited three ABX3 systems (see Table 1) as a result of nonplanarity enforced by the crowding of the ester groups.7 Compounds 4c–e are unsymmetrical and exhibit more complicated, but resolved, 1H and 13C spectra (see Table 1).The structural assignments made on the basis of the NMR spectra of compounds 4a–e were supported by measure- *To receive any correspondence. †This is a Short Paper as defined in the Instructions for Authors, Section 5.0 [see J.Chem. Research (S), 1997, Issue 1]; there is therefore no corresponding material in J. Chem. Research (M). Table 1 1H and 13C NMR data for compounds 4a–e Compound 1H/13C d (ppm) (CDCl3–Me4Si) 4a 1H 3.37, 3.99 and 4.03(18 H, 3 s, 6 OCH3), 8.06 (2 H, d, J 9.2 Hz, C2-H and C5-H), 8.10 (2 H, s, C3-H and C4-H), 8.66 (2 H, d, J 9.2 Hz, C1-H and C6-H) 13C 51.48, 51.95 and 52.78 (6 OCH3), 106.44 (2 C), 118.14 (2 CH), 120.07 and 124.82 (4 C), 126.58 (2 CH), 126.92 (2 C), 127.56 (2 CH), 131.08 and 137.62 (4 C), 158.16, 163.64 and 166.26 (6 C�O) 4b 1H 1.166 (6 H, t, J 7.2 Hz, 2 CH3), 1.440 (6 H, t, J 7.2 Hz, 2 CH3), 1.474 (6 H, J 7.2 Hz, 2 CH3), 3.73 and 3.79 (4 H, q of AB system, JAB µ10.8, J 7.2 Hz, 2 CH2), 4.434 and 4.468 (4 H, q of AB system, JAB µ10.8, J 7.2 Hz, 2 CH2), 4.441 and 4.480 (4 H, q of AB system, JAB µ10.7, J 7.2 Hz, CH2), 8.040 (2 H, d, J 9.2 Hz, C2-H and C5-H), 8.070 (2 H, s, C3-H and C4-H), 8.67 (2 H, d, J 9.2 Hz, C1-H and C6-H) 13C 13.80, 14.23 and 14.42 (6 CH3), 60.67, 60.70 and 61.62 (6 CH2), 107.76 (2 C), 118.02 (2 CH), 120.58 and 125.45 (4 C), 126.56 and 127.08 (4 CH), 127.52, 131.25 and 138.12 (6 C), 157.65, 164.10 and 166.06 (6 C�O) 4c 1H 2.95 (3 H, s, CH3), 3.35, 3.38, 3.98, 4.00, 4.04 and 4.05 (18 H, 6 s, 6 OCH3), 7.94 (1 H, s, C4-H), 8.02 and 8.62 (2 H, AB system, J 9.0 Hz, CHCH), 8.24 and 8.68 (2 H, AB system, J 9.2 Hz, CHCH) 13C 19.46 (CH3), 51.35, 51.40, 51.98, 52.00, 52.65 and 52.70 (6 OCH3), 106.50, 106.57, 117.56, 118.09, 119.35, 121.59, 123.18, 123.79, 124.65, 126.19, 126.64, 127.05, 130.07, 130.39, 132.95, 136.82, 136.93, and 138.33 (18 C), 157.43, 157.45, 163.45, 163.48, 165.77 and 165.82 (6 C�O) 4d 1H 3.36, 3.38, 4.00, 4.03, 4.06 and 4.07 (18 H, 6 s, 6 OCH3), 7.97 and 8.67 (2 H, AB system, J 9 Hz, C1-H and C2-H), 8.20 (1 H, s, C4-H), 8.52 and 8.73 (2 H, AB system, J 9.2 Hz, C5-H and C6-H) 13C 51.46, 51.50, 52.02, 52.10, 52.65 and 52.70 (6 OCH3), 107.01, 107.18, 118.62, 118.86, 119.39, 119.56, 123.14, 123.75, 124.93, 125.20, 125.28, 126.19, 125.56, 129.41, 130.43, 130.84, 136.75 and 136.86 (18 C), 157.35, 157.45, 163.16, 163.22, 165.49 and 165.62 (6 C�O) 4e 1H 3.36, 3.39, 4.00, 4.02, 4.05, and 4.06 (18 H, 6 s, 6 OCH3), 8.15 and 8.78 (2 H, AB system, J 9.0 Hz, C1-H and C2-H), 8.82 (1 H, s, C4-H), 8.81 and 8.88 (2 H, AB system, J 9.1 Hz, C1-H and C3-H) 13C 51.46, 51.55, 52.20, 52.25, 52.74 and 52.82 (6 OCH3), 107.67, 107.72, 119.72, 120.00, 120.29, 121.55, 122.49, 122.94, 124.52, 124.89, 126.45, 126.60, 130.12, 131.12, 133.49, 136.21, 137.43 and 143.13 (18 C), 157.06, 157.20, 162.76, 162.84, 164.92 and 165.00 (6 C�O).J.CHEM. RESEARCH (S), 1997 213 ments of their IR and UV spectra. Of special interest is the carbonyl absorption (1698–1748 cmµ1) for these compounds. Conjugation with the heterocyclic ring appears to be a plausible factor in the reduction of the wave numbers of the carbonyl absorption bands.8 The electronic spectra of compounds 4a,b each exhibited bands at 237–340 nm owing to the dipyrrolophenanthroline nucleus.The reactions described herein represent a simple and efficient synthesis of functionalized dipyrrolophenanthrolines. Experimental Melting points were measured on an Electrothermal 9100 apparatus and are uncorrected. Elemental analyses for C, H and N were performed using a Heraeus CHN-O-Rapid analyser. IR spectra were measured on a Shimadzu IR-460 spectrometer.UV spectra were measured using solutions in ethanol (95%) on a Shimadzu UV-2100 spectrometer. 1H and 13C NMR spectra were measured with a JEOL EX-90A spectrometer at 90 and 22.6 MHz, respectively. The 1H NMR spectrum of 4b was recorded at 400 MHz using a Varian Unity Plus NMR spectrometer. Mass spectra were recorded on a Finnigan-Matt 8430 mass spectrometer operating at an ionization potential of 70 eV. 1,10-Phenanthrolines 2a–d and dialkyl acetylenedicarboxylates 3a,b were obtained from Fluka (Buchs, Switzerland) and were used without further purification.Typical preparation of hexamethyl dipyrrolo[1,2-a:2p,1p-k][1,10] phenanthroline-7,8,9,12,13,14-hexacarboxylate (4a).·To a magnetically stirred solution of 1,10-phenanthroline (0.18 g, 1 mmol) in methanol (10 ml) was added dropwise a mixture of dimethyl acetylenedicarboxylate (0.71 g, 5 mmol) in methanol (2 ml) at room temperature and the mixture refluxed for 24 h.After 24 h in a refrigerator at 5 °C, a yellow solid (0.31 g, yield 52%, mp 205–207 °C) was collected by filtration. Recrystallization from methanol yielded 4a as pale yellow crystals (0.28 g), mp 209–211 °C; vmax (KBr)/cmµ1 1745, 1720 and 1698 (C�O); 1240 and 1174 (C·O); lmax/nm (log e) 237 (4.7), 2.8), 289 (3.1), 336 (2.2); MS (m/z, %): 604 (M+, 2), 430 (25), 415 (56), 353 (100), 149 (45), 105 (60) (Found: C, 59.7; H, 4.1; N, 4.7. C30H24N2O12 requires C, 59.61; H, 4.00; N, 4.63%).Selected data for 4b.·Yellow crystals, 0.4 g, yield 58%, mp 183–185 °C; vmax (KBr)/cmµ1 1748, 1741 and 1703 (C�O); 1231 and 1180 (C·O); lmax/nm (log e) 238 (4.5), 270 (2.6), 285 (3.0), 340 (2.5); MS (m/z, %): 688 (M+, 1), 387 (10), 368 (25), 324 (22), 282 (33), 150 (42), 57 (100) (Found: C, 62.1. C36H36N2O12 requires C, 62.83; H, 5.27; N, 4.07%). Selected data for 4c.·Dark-yellow powder, 0.27 g, yield 44%, mp 265 (decomp.); vmax (KBr)/cmµ1 1741, 1735 and 1699 (C�O); 1213 and 1195 (C·O); MS (m/z, %): 619 (M++1, 8), 560 (40), 516 (35), 501 (100), 470 (28), 457 (18), 267 (35) (Found: C, 59.9; H, 4.3; N, 4.7.C31H26N2O12 requires C, 60.20; H, 4.24; N, 4.53%). Selected data for 4d.·Pale yellow powder, 0.26 gm, yield 40%, mp 256 °C (decomp.); vmax(KBr)/cmµ1 1746, 1738 and 1700 (C�O); 1221 and 1174 (C·O); MS (m/z, %): 638 (M+, 15), 579 (25), 535 (38), 520 (100), 489 (35), 286 (82), 149 (42), 144 (76) (Found: C, 56.4; H, 3.7; N, 4.2. C30H23N2O12Cl requires C, 56.39; H, 3.63; N, 4.38%).Selected data for 4e.·Yellow powder, 0.21 g, yield 32%, mp 280 °C (decomp.); vmax (KBr)/cmµ1 1745, 1731 and 1702 (C�O); 1212 and 1168 (C·O); MS (m/z,%): 649 (M+, 5), 590 (12), 546 (55), 531 (100), 485 (26), 310 (38), 251 (42), 149 (90) (Found: C, 55.6; H, 3.6, N, 6.5. C30H23N3O14 requires C, 55.48; H, 3.57; N, 6.47%). Received, 28th February 1997; Accepted, 12th March 1997 Paper E/7/01417A References 1 R. M. Acheson and N. F. Elmore, Adv. Heterocycl. Chem., 1978, 23, 263. 2 R. M. Acheson and J. M. Woollard, J. Chem. Soc. C, 1971, 3296; R. M. Acheson and G. A. Taylor, J. Chem. Soc., 1960, 1691. 3 A. Crabtree, A. W. Johnson and J. C. Tebby, J. Chem. Soc., 1961, 3497. 4 F. J. Swinbourne, J. H. Hunt and G. Klinkert, Adv. Heterocycl. Chem., 1978, 23, 103. 5 W. Flitsh, in Comprehensive Heterocyclic Chemistry, ed. A. R. Katritzky and C. W. Rees, Pergamon, London, 1984, vol. 3, pp. 443–470. 6 L. A. Summers, Adv. Heterocycl. Chem., 1977, 22, 1. 7 E. L. Eliel and S. H. Wilen, Stereochemistry of Organic Compounds, Wiley, New York, 1994, pp. 1163–1166. 8 R. M. Silverstein, G. C. Bassler and T. C. Morril, Spectrometric Identification of Organic Compounds, Wiley, New York, 5th edn., 1991, p