New synthesis of tetraazachlorins and tetraazabacteriochlorins by Diels–Alder reaction of tetraazaporphine

Abstract

<jats:p> The use of the Diels–Alder reaction of unsubstituted tetraazaporphine as dienophile with some dienes of the anthracene series for the synthesis of novel substituted tetraazachlorins, tetraazabacteriochlorins and tetraazaisobacteriochlorins is reported. The condensation of tetraazaporphine with anthracene, 9,10-dimethyl- or 2,6-di(tert-butyl)anthracene in boiling chlorobenzene gives novel dibenzobarreleno-substituted tetraazachlorins 3–5 in yields of up to 71%. When AlCl<jats:sub>3</jats:sub> was used as catalyst in the reaction of tetraazaporphine with 2,6-di(tert-butyl) anthracene, the corresponding cis- and trans-dibenzobarreleno-substituted tetraazabacteriochlorins 6a and 6b were obtained. The reaction of tetraazaporphine with the more active diene 2,3-benzanthracene at 130°C gives mainly benzonaphtho[2,3-b]barreleno-substituted tetraazachlorin 7, while the same reaction conducted at 220°C led to a mixture of cis- and trans isomers of tetraazabacteriochlorins 8a and 8b and tetraazaisobacteriochlorins 9a and 9b. The products were characterized using elemental analysis data and mass, <jats:sup>1</jats:sup>H NMR and visible spectra. The effect of hydrogenation of one or two double bonds of the tetraazaporphine macrocycle on the electronic absorption spectra is discussed. </jats:p>

Synthesis and Spectroscopic and Electrochemical Studies of Pyrazine- or Pyridine-Ring-Fused Tetraazachlorins, Bacteriochlorins, and Isobacteriochlorins

“…Figure shows the absorption and MCD spectra of the compounds reported in this study. Similarly to the results from our previous study, the TACs and TABCs show split Q bands, whereas the TAiBCs have single, intense Q bands. ,, Oppositely signed MCD signals corresponding to the Q-band components of the TACs and TABCs are observed, with the longer wavelength components always having a negative sign, suggesting that the energy difference between the HOMO and HOMO−1 (ΔHOMO) is larger than that of the LUMO and LUMO+1 (ΔLUMO) . The Soret region (ca.…”

“…However, these hydrogenated compounds were too unstable to be isolated and characterized, and it is known today that their characterizations were incorrect . Recently, our group has succeeded in obtaining chemically stable TAC derivatives by employing Diels−Alder addition of dienophiles to the TAP skeleton or by using tetramethylsuccinonitrile as a source of the hydrogenated sites. − These methodologies enabled us to isolate and fully characterize the TAC, TABC, and TAiBC skeletons, and their benzo-, 2,3-naphtho-, or 1,2-naphtho-fused derivatives. Our group has also reported C 60 -containing TAC, TABC, and TAiBC derivatives, in which 1,2-dicyanofullerene was employed as the source of the hydrogenated sites, and proved that these conjugates show large molecular orbital (MO) interactions between the constituting units. , …”

Design and synthesis of tetraazachlorins, tetraazabacteriochlorins and tetraazaisobacteriochlorins

“…Self-condensation of 3 in the presence of magnesium formate in a boiling mixture of nitrobenzene and 2-ethoxyethanol led to a low yield of magnesium TAP. Subsequently, we have investigated self-condensation of succinonitrile (6) with two reagent and solvent systems: lithium dimethylaminoethoxide (LiDMAE) in boiling dimethylaminoethanol or with lithium pentoxide in pentanol and two different atmospheres: inert and also with simultaneous oxidation of the intermediate hydrogenated forms by oxygen (Scheme 3) [17]. We not only succeeded in increasing the yield of TAP (7) up to 15%, but we have also prepared the previously unknown TAC (8) by the direct method when the reaction was carried out in an argon atmosphere.…”

“…The presence of quaternary carbon atoms with four geminal methyl groups effectively prevents transformation of the formed macrocycles into the corresponding TAP derivatives. Syntheses of metal-free benzo-or 2,3-naphtho-fused TACs were performed by the reaction of 9 and phthalonitrile (10) or 2,3-dicyanonaphthalene (11) in the presence of LiDMAE in boiling dimethylaminoethanol (Scheme 4) [18][19][20]. In spite of the fact that triareno-fused TACs (12,13) were obtained in low yields (~ 2%), due to features of the molecular structures, their separation from the lower soluble main products Pc or 2,3-naphthalocyanine (Nc 2,3 ) was relatively easy by extraction with chlorobenzene or trichlorobenzene, followed by column chromatography on alumina.…”

“…For example, the Q 1 band is located at 724 and 842 nm respectively for nickel complexes of benzo-fused TAC (14a) and TABC (15a) (Fig. 5), while the same band of linearly annelated 2,3-naphthalene TAC (17) and TABC (18) is shifted bathochromically to 806 and 892 nm (Fig. 6).…”