(College of Chemistry and Chemical Enfineering of Nantong University, Nantong 226007, Jiangsu, China) Received Jul. 1, 2004; Financial assistance from Education Department of Jiangsu Province (No. 01KJD150005). Abstract Ceric ammonium nitrate efficiently catalyzes the reaction of pyrrole with various aldehydes to afford the corresponding dipyrromethane in good yield and they are used in the preparation of porphyrins.Keywords Ceric ammonium nitrate, pyrrole, dipyrromethane, porphyrin 1 INTRODUCTION 2 EXPERIMENTAL 3 RESULTS AND DISCUSSION Table 1 Synthesis of dipyrromethanes
Most of the dipyrromethanes are indefinitely stable in the purified form upon storage at 0oC in the absence of light. 3.2 Characteristics results meso-Phenyldipyrromethane (3a): (53%) as pale yellow crystals; mp: 100-101ºC; 1H NMR (CDCl3): d 5.48 (s, 1 H), 5.92 (s, 2 H,), 6.16 (q, J=2.8 Hz, 2 H), 6.70 (d, J=1.2 Hz, 2 H), 7.21-7.32 (m, 5 H), 7.92 (br s, 2 H); HRMS: m/z cacld for C15H14N2: 222.1157, found: 222.1190. Anal. Calcd. for C15H14N2: C, 81.05; H, 6.35; N, 12.60. Found: C, 80.10; H, 6.32; N, 12.48. meso -(p-tolyl)dipyrromethane (3b). (76.45%) as tan solid: mp 110-111ºC; 1H NMR (CDCl3) d 2.35 (s, 3 H), 5.46 (s, 1 H), 5.94 (s, 2 H) 6.17 (q, J= 3.2 Hz, 2 H), 6.70 (q, J= 2.8 Hz, 2 H), 7.15 (dd, J= 2.8 Hz and 3.6 Hz, 4 H), 7.92(br s, 2H); HRMS (EI+) cacld for C16H16N2: 236.1313, found 236.1336. Anal. Calcd. for C16H16N2: C, 81.32; H, 6.82; N, 11.85. Found: C, 81.40; H, 6.89; N, 11.71. meso -(p-chlorophenyl)dipyrromethane (3c). (54.37%) as light yellow solid: mp 112-113ºC; 1H NMR (CDCl3) d 5.44 (s, 1 H), 5.88 (s, 2 H), 6.16 (q, J=2.8 Hz, 2 H), 6.70 (d, J=1.2 Hz, 2 H), 7.09-7.14 (m, 2 H), 7.24-7.29(m, 2 H), 7.93 (br s, 2 H); HRMS (EI+) cacld for C15H13N2Cl: 256.0767, found 256.0795. Anal. Calcd. for C15H13N2Cl: C, 70.18; H, 5.10; N, 10.91. Found: C, 70.06; H, 5.15; N, 10.86. meso -(p-bromophenyl)dipyrromethane (3d). (55.68%) as white solid: mp 125-126ºC; 1H NMR (CDCl3) d 5.43 (s, 1 H), 5.86(d, 2 H), 6.15 (q, J= 2.8 Hz, 2 H), 6.68 (d, J= 1.6 Hz, 2 H), 7.10 (m, 2 H), 7.24(m, 2H), 7.92 (br s, 2 H); HRMS (EI+) cacld for C15H13N2Br 300.0262 ,found 300.0289. Anal. Calcd. for C15H13N2Br: C, 59.82; H, 4.35; N, 9.30. Found: C, 59.84; H, 4.30; N, 9.38. meso -(p-iodophenyl)dipyrromethane (3e). (54.37%) as light tan solid: mp 145-147 ºC; 1H NMR (CDCl3) d 5.42 (s, 1 H), 5.86 (s, 2 H), 6.14 (q, J= 2.8 Hz, 2 H), 6.65 (d, J= 1.8 Hz, 2 H), 6.99 (m, 2 H), 7.58(m, 2 H), 8.42 (br s, 2 H); HRMS (EI+) cacld. C15H13N2I 348.0123, found 348.0101. Anal.Calcd. for C15H13N2I: C, 51.74; H, 3.76; N, 8.05. Found: C, 51.79; H, 3.80; N, 8.06. meso -(o-nitrophenyl)dipyrromethane (3f). (57.57%) as yellow solid: mp 145-147ºC; 1H NMR (CDCl3) d 5.86 (s, 2 H), 6.15 (q, J= 2.8 Hz, 2 H), 6.20 (s, 1 H), 6.71 (d, J= 1.6 Hz, 2 H), 7.26 (dd, J= 3.2 Hz and 6.8 Hz, 1 H), 7.36-7.40 (m, 1 H ), 7.49-7.52 (m, 1H), 7.86 (dd, J= 0.8 Hz and 0.4 Hz, 1H), 8.16 (br s, 2 H); HRMS (EI+) cacld. C15H13N3O2 :267.1008, found 267.1029. Anal. Calcd. for C15H13N3O2: C, 67.40; H, 4.90; N, 15.72 Found: C, 67.53; H, 4.72; N, 15.64. meso -(p-nitrophenyl)dipyrromethane (3g). (65.78%) as green solid: mp 159-160ºC; 1H NMR (CDCl3) d 5.58 (s, 1 H), 5.87 (s, 2 H), 6.17 (q, J= 2.4 Hz, 2 H), 6.75 (d, J= 1.8 Hz, 2 H), 7.37 (d, J= 8.4 Hz 2 H), 8.02 (br s, 2 H), 8.17(d, J= 8.8 Hz, 2 H); HRMS (EI+) cacld. C15H13N3O2 :267.1008, found 267.1030. Anal. Calcd. for C15H13N3O2: C, 67.40; H, 4.90; N, 15.72 Found: C, 67.25; H, 4.95; N, 15.58. meso -(p-tert-butyphenyl)dipyrromethane (3h). (38.12%) as pale yellow crystals: mp 160-161ºC; 1H NMR (CDCl3) d 1.31 (s, 9 H), 5.47 (s, 1 H), 5.92 (m, 2 H), 6.15 (q, J= 3.2 Hz, 2 H), 6.70 (m, 2 H), 7.12 (m, 2 H), 7.32(m, 2 H), 7.92 (br s, 2 H); HRMS (EI+) cacld. C19H22N2:278.1783, found 278.1798. Anal. Calcd. for C19H22N2: C, 81.97; H, 7.97; N, 10.06. Found: C, 81.93; H, 7.95; N, 10.12. meso -(p-methoxyphenyl)dipyrromethane (3i). (68.83%) as colorless solid: mp 99-100ºC; 1H NMR (CDCl3) d 3.79 (s, 3 H), 5.42 (s, 1 H), 5.91 (m, 2 H), 6.15 (q, J=2.8 Hz, 2 H ), 6.68 (m, 2 H), 6.85 (m, 2 H), 7.12 (m, 2 H), 7.91 (br s, 2 H); HRMS (EI+) cacld. C16H16N2O :252.1263, found 252.1238. Anal. Calcd. for C15H12N2O2: C, 76.16; H, 6.39; N, 11.10. Found: C, 76.20; H, 6.35; N, 11.00. meso -(mesityl)dipyrromethane (3j). (55.32%) as pale yellow solid: mp 171-172ºC; 1H NMR (CDCl3) d 2.04 (s, 6 H), 2.27 (s, 3 H), 5.92 (s, 1 H), 6.03 (m, 2 H), 6.17 (m, 2 H), 6.65 (m, 2 H), 6.86(s, 2 H), 7.95 (br s, 2 H); HRMS (EI+) cacld. C18H20N2 :264.1626, found 264.1604. Anal. Calcd. for C15H13N3O2: C, 81.78; H, 7.62; N, 10.60 Found: C, 81.80; H, 7.66; N, 10.54. 3.3 Preparation of trans-substituted porphyrin from dipyrromethanes A dipyrromethane can be condensed with an aldehyde to afford the trans-substituted prophyrin (Scheme 2). Results are summarized in Table 2. Scheme 2 Table 2 Synthesis of porphyrins
4 CONCLUSION
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