Preparation of macrocyclic compounds by thermal dimerization of 1,10-phenanthroline derivatives

摘要

214 J.C.S. Perkin IPreparation of Macrocyclic Compounds by Thermal Dimerization ofI ,lo-Phenanthroline Derivatives.By Shojiro Ogawa, Institute of industrial Science, University of Tokyo, Roppongi, Minato-ku, Tokyo, JapanAn efficient non-template synthesis of a new macrocycle. a conjugated tautomer of 1 ,I 4 :7,8-diethenotetrapyrido-2,1,6-cd:2',1',6'-gh :2",1",6"-jk:2" ',I " ',6" '-na I ,4,8,1 1 tetra-azacyclotetradecine (3). is described. The ther-mal behaviour of several disubstituted 1 ,I 0-phenanthrolines towards dimerization is studied by use of differentialthermal analysis and thermogravimetric analysis, and some spectroscopic properties of the macrocycles producedare described.AZAMACROCYCLIC systems have been intensively investi-gated in attempts to correlate their electronic propertiesand reactivities with those of polypyrrolic macrocyclessuch as porphins and corroles.Although a number ofmethods have been developed for the preparation ofazamacrocylic systems, non-template preparations offree macrocycles usually have the disadvantage that themethod gives only low yield of the desired pr0ducts.lWe have recently reported a synthesis of a conjugatedtautomer of a diethenodipyridohexa-azacyclotetradecineby condensing 2,9-diamino-1, 10-phenanthroline with a2,9-dihalogeno-l,lO-phenanthroline in the presence ofI 1 Ialkali in nitrobenzene, and its behaviour as a ligand.22,9-Diamino-1 ,lo-phenanthroline alone also gave acyclic dimer when heated without solvent. We describehere the thermal behaviour of several disubstituted1,lO-phenanthrolines, leading to the formation of a newmacrocycle.The study was conducted by use ofHevolution of ammonia. These needles were shown to bethe hexa-aza-macrocycle (1). The reaction was studiedby DTA and TGA.A thermogram of DAP shows a melting endotherm at292 "C, followed by exothermic macrocycle formationat 306 "C and a small endothermic peak at 326 "C. TheTGA curve consists of two continuous steps, whichmight be interpreted in terms of a two-step deamination-condensation. The weight loss in the range 290-330 "Ccorresponds to 1 mol of ammonia per mol of DAP.The thermogram for an equimolar mixture of DAP and2,9-dichloro-1, 10-phenanthroline (DCP) shows an endo-therm at 224 "C and a complex exotherm beginning at230 "C with a peak at 280 "C.The TGA curve shows nosubstantial weight decrease. This implies that cross-condensation between DAP and DCP rather than self-condensation of DAP occurs. When an equimolarmixture of DAP and DCP was heated at 300 "C, needlesseparated from the melt with slight evolution of gas.Analysis showed that the needles were the dihydro-chloride of the hexa-aza-macrocycle (2).The freebase (1) was obtained as a precipitate by treating theaqueous solution with alkali. The i.r. spectrum ofthe free base (1) shows bands at 2 780 and 900 cm-l,assigned to stretching and out-of-plane deformationThis salt (2) is moderately soluble in water.differential thermal analysis (DTA) , thermogravimetricanalysis (TGA) , and spectroscopy.When 2,9-diamino-l,lO-phenanthroline (DAP) washeated slightly above its m.p., the formation of needlecrystals was observed just after melting, with vigorous1 J.J. Christensen, D. J. Eathough, and R. M. Izatt, Chern.S. Ogawa, T. Yamaguchi, and N. Gotoh, J.C.S. Perkin I ,Rev., 1974, 74, 353.1974, 976.N-H vibrations, which disappear on N-deuteriation.The vNH value is much lower and the 8NH value muchhigher than those of porphyrins (near 3 310 cm-l andbetween 680 and 675 cm-l, respectively 3). This maybe explained in terms of strong intramolecular hydrogenbonding. The salt (2) shows a very intense N-Hstretching band at 2 780 cm-l; this high frequency in3 W. S . Caughey, J. 0. Alben, W. Y . Fujimoto, and J.L.York. J . Org. Chem., 1966, 31, 26311977 215comparison with pyridinium salts (2 325-2 500 cm-l)may be due to a contribution from the resonance struc-ture (27, strengthening the outer N-H bond. Thefact that the N-H out-of-plane bending band at 910cm-l is very weak supports this idea. The lH n.m.r.spectrum of the free base in trifluoroacetic acid in whichit is assumed that the compound is present as the dication(2) shows that the inner NH protons are abnormallydeshielded ( T -8.5); in other words these protons arevery acidic and the contribution of (2rsquo;) is important.Since the amine bridge structure (2rsquo;) is less effectivelyelectron-delocalized than imine bridge structure (1), ahypsochromic shift is expected in the U.V. spectrum ofthe salt relative to the free base (1); this is in factobserved (see Figure).The ease of cyclisation of DAP to the hexa-aza-macrocycle led us to examine the possibility of co-cyclisation of 2,9-dimethyl-l , 10-phenanthroline (DMP)and DCP to give a methine-bridged tetra-aza-macro-cycle.However, our attempts to condense DMPwith DCP in solution were unsuccessful. Nevertheless,a thermogram of anshows endothermsequimolar mixture of DMP and DCPat 118 and 193 ldquo;C and a distinct250 OC, and this was the case. The reaction gave a redproduct and its structure was confirmed as (3) byelemental analysis and spectral evidence.The elimination of hydrogen chloride in this reactionis in contrast to the reaction of DAP and DCP, whichshows little weight loss on the exothermic reaction.The mass spectrum of the product shows the molecularion at m/e 384 and also an intense doubly charged mole-cular ion at m/e 192.The IH n.m.r. spectrum could notbe determined owing to solubility problems.In marked contrast to the hexa-aza-macrocycle (l),which gives a yellow solution in chloroform, the tetra-aza-macrocycle (3) gives an intensely red solution. Theelectronic spectrum of (3) is .qualitatively similar tothat of (1) (see Figure). The bathochromic shift withrespect to the hexa-aza-macrocycle, might be due tomore effective electron delocalization in the former.In the i.r. spectrum of (3) the vNH band is too weak tobe observed. Bands at 1 280 and 960 cm-1 were assignedto N-H in-plane and out-of-plane deformation, respect-ively, on the basis of their disappearance on deuteriationeffected by treating (3) with D,SO, and then with K,-CO, in D,O.The tetra-aza-macrocycle (3) is stable inamp;)amp;amp;exotherm at 269 ldquo;C. The TGA curve shows weight lossat 45-120 ldquo;C corresponding to 0.5 mol of water perElectronic spectra of the hexa-aza-macrocycle ( 1) in chloroform,the tetra-aza-macrocycle (3) in methanol, and the hexa-aza-macrocycle dihydrochlonde (2) in watermol of DMP hemihydrate, and another weight loss at ca.250 ldquo;C. The second weight loss corresponded to 2 molof hydrogen chloride per mol each of DMP and DCP.This suggested than an equimolar mixture of DMP andDCP would give a macrocycle (3) on heating at ca.the dark, but the absorption spectrum changed signifi-cantly when the solution was exposed to light.Thephotochemistry of this system will be reported in a forth-coming paper.EXPERIMENTALThermal analysis was conducted by using a Thermoflex8021 instrument (Rigaku Denki) under nitrogen at aheating rate of 5 ldquo;C min-1. Sample size was in the range83.0-200 mg. Equimolar proportions of reactants weremixed thoroughly in a mortar. N.m.r. spectra weredetermined with a Hitachi R-20A instrument operating at60 MHz, with tetramethylsilane as internal reference. U.V.and visible spectra were measured with a Union GikenSM 401 spectrophotometer. 1.r. spectra were measuredwith a Hitachi-Perkin-Elmer 125 spectrophotometer.Mass spectra were obtained by direct insertion into theion source of a Hitachi RMU-61) instrument.2,9-Dichloro- and 2,g-diamino- 1,lO-phenanthroline wereprepared by published methods.2 2,9-Dimethyl-I , 10-phenanthroline hemihydrate was obtained commercially(Tokyo Kasei Kogyo Co., Tokyo), and was used withoutfurther purification.Dihydrochloride of 1,14 : 7,8-Diethenotetraf1yrid02,1,6-de :2rsquo;1rsquo;,6rsquo;-gh : 2rdquo;,1rdquo;,6rdquo;-kl : 2rdquo; rsquo;,lrdquo; rsquo;,6rdquo; rsquo;-na1,3,5,8,10,12-hexa-azacyczotetradecine (2)-2,9-Diamino- 1, lo-phenanthro-line (42 mg) and 2,9-dichloro-l, 10-phenanthroline (50 mg)L.J. Bellamy, lsquo; The Infra-red Spectra of Complex Mole-cules,rsquo; 2nd edn., Wiley, New York, 1958, p. 260216 J.C.S. Perkin Iwere mixed thoroughly in a mortar and heated in an atmos-phere of nitrogen. Yellow needles began to separate at230 ldquo;C.After solidification was completed, heating wascontinued a t 260 ldquo;C for 1 h. The product was washed withchloroform, giving yellow needles (77 mg, 83.7) (Found:C, 63.4; H, 3.6; N, 18.8. C,,H,,Cl,N, requires C, 62.8;H, 3.5; N, 18.3). The free base (l), identical with thesample already prepared,2 was obtained by dissolving thesalt (50 mg) in water (100 ml) and adding aqueous ammonia(d 0.88; 5 ml) in water (10 ml).Conjugated Tautomer of 1,14 : 7,8-Diethenotetrapyrido-2,1,6-cd : 2rsquo;,1rsquo;,6rsquo;-gh : 2rdquo;,1rdquo;,6rdquo;-jk : 2rdquo; rsquo;,1rdquo; rsquo;,6rdquo; rsquo;-na1,4,8,-1 ltetra-uzacyclotetradecine (3) .-A mixture of 2, g-dimethyl-1,lO-phenanthroline hemihydrate (83 mg) and 2,g-dichloro-1,lO-phenanthroline (70 mg) was heated to 260 ldquo;C in anatmosphere of nitrogen. After the vigorous evolution ofhydrogen chloride ceased, heating was continued at 260 ldquo;Cfor a further 4 h. The solidified mixture was washed withacetone, giving red crystals (101 mg, 93.6) (Found: C,80.85; H, 4.45; N, 14.75. C,,H,,N, requires C , 81.2;H, 4.2; N, 14.6).I thank Mr. K. Kataoka for experimental assistance andProfessors J. Kumanotani and S. Shiraishi for comments.6/542 Received, 22nd March, 19760 Copyright 1977 by The Chemical Societ