Manley Jerad M, Roper Tracy J, Lash Timothy D
Department of Chemistry, Illinois State University, Normal, IL 61790-4160, USA.
J Org Chem. 2005 Feb 4;70(3):874-91. doi: 10.1021/jo040269r.
Porphyrins built up from two naphtho[1,2-c]pyrrole subunits and two beta-substituted pyrroles can produce five isomeric dinaphthoporphyrin systems. To gain insights into the effects of ring fusion on extended porphyrin chromophores, all five of these systems were synthesized in isomerically pure form. In four of these syntheses, dihydronaphthopyrroles were used to introduce one or both of the naphthalene subunits, and dehydrogenation with DDQ in refluxing toluene later produced the fully conjugated systems. Naphthopyrroles were also prepared by reacting isocyanoacetate esters with 1-nitronaphthalene in the presence of a phosphazene base. These compounds proved to be less stable than their dihydronaphthopyrrolic counterparts but could still be utilized in these synthetic studies. Three isomeric adj-dinaphthoporphyrin systems were prepared using the MacDonald "2 + 2" condensation or by the cyclization of a,c-biladiene intermediates with copper(II) chloride or AgIO(3)-Zn(OAc)(2). A dinaphthoporphyrin with two naphthalene units pointing toward one another could only be obtained in low yields due to a combination of stability and steric factors, but the other two adj-difused systems were isolated in good overall yields. However, the final dehydrogenation step occurred in moderate yields (50-60%) and could only be performed when the porphyrins bore propionate ester side chains that produced sufficient solubility in organic solvents. The two related opp-dinaphthoporphyrins were synthesized by a "head-to-tail" self-condensation of a dipyrrylmethane aldehyde, or a "3 + 1" synthesis using a tripyrrane intermediate bearing two fused dihydronaphthalene moieties, in excellent yields. In both cases, a final dehydrogenation step was required, but the opp-dinaphthoporphyrins were consistently formed in virtually quantitative yields. The opp-dinaphthoporphyrin series gave UV-vis spectra with relatively strong Soret bands at 425 nm, and the visible region was dominated by an unusually strong Q-band III. The adj-dinaphthoporphyrins produced broader less intense Soret bands and four well-defined Q-bands, including a relatively strong absorption at 645 nm. However, the relative orientation of the naphthalene rings had no significant effects on these spectra. On the other hand, the dications produced in TFA-chloroform solutions showed more discrimination between the individual porphyrin systems, and the metallo derivatives also displayed significant variations in their electronic absorption spectra.
由两个萘并[1,2 - c]吡咯亚基和两个β - 取代吡咯构建的卟啉可以产生五种异构的二萘卟啉体系。为了深入了解环融合对扩展卟啉发色团的影响，所有这五种体系均以异构体纯形式合成。在其中四种合成中，二氢萘并吡咯用于引入一个或两个萘亚基，随后在回流甲苯中用DDQ脱氢生成完全共轭体系。萘并吡咯也通过异氰基乙酸酯与1 - 硝基萘在磷腈碱存在下反应制备。这些化合物被证明比其二氢萘并吡咯对应物更不稳定，但仍可用于这些合成研究。使用麦克唐纳“2 + 2”缩合或通过a,c - 联二烯中间体与氯化铜(II)或AgIO(3)-Zn(OAc)(2)环化制备了三种异构的邻位 - 二萘卟啉体系。由于稳定性和空间因素的综合作用，只能以低产率获得两个萘单元彼此指向的二萘卟啉，但另外两个邻位 - 扩散体系以良好的总产率分离出来。然而，最后的脱氢步骤产率适中（50 - 60%），并且只有当卟啉带有在有机溶剂中产生足够溶解度的丙酸酯侧链时才能进行。两种相关的对位 - 二萘卟啉通过二吡咯甲烷醛的“头对尾”自缩合或使用带有两个稠合二氢萘部分的三吡咯中间体的“3 + 1”合成以优异的产率合成。在这两种情况下，都需要最后的脱氢步骤，但对位 - 二萘卟啉始终以几乎定量的产率形成。对位 - 二萘卟啉系列在425 nm处给出具有相对较强Soret带的紫外 - 可见光谱，并且可见区域由异常强的Q带III主导。邻位 - 二萘卟啉产生更宽、强度更低的Soret带和四个明确的Q带，包括在645 nm处的相对较强吸收。然而，萘环的相对取向对这些光谱没有显著影响。另一方面，在TFA - 氯仿溶液中产生的二价阳离子在各个卟啉体系之间表现出更多差异，并且金属衍生物在其电子吸收光谱中也显示出显著变化。
