Synthesis of the novel fused pi-electronic systems by the intramolecular electrophilic attack of tropylium ion

含七元环的稠合全pi共轭体系由于其独特的电子结构而成为理论和实验上感兴趣的分子，并且已经制备了各种这类化合物。然而，已报道的合成方法在不饱和七元环的构建阶段普遍存在步骤繁琐和产率低的问题。我们注意到三联吡啶离子的亲电性，并开发了两种简便的合成方法来合成含共轭七元环的化合物。我们的合成策略是使用市售的1，3，5-环庚三烯作为七元单元。1)通过邻芳基和邻杂芳基对甲苯的分子内Friedel-Craft型反应，简便、新颖地合成了含托吡啶离子的稠合全共轭环化合物。以合理的产率得到了三苯的等电子阳离子环庚烷[a]硫代萘和环庚烷[a]呋喃并[a]萘离子，以及具有致癌活性的环庚烷[a]苯并[c]萘离子、环庚烷[α]苯并[c]并[c]萘离子和环庚烷[a]并[c]并[c]萘正离子。2)合成了新的杂七氮杂衍生物--β-(10-苯并[a]-天青基)-、b-不饱和酮和β-(9-天青[1，2-b]硫基)。分别从欧米隆-[2-呋喃]对甲苯和1-对呋喃-2-[2-呋喃]噻吩制得β-不饱和酮，产率合理。通过分子内分子内对呋喃环2位的攻击，推测了一种新的环化反应机理。测定了两个β-(9-偶氮烯并[1，2-b]噻吩基)-α，β-不饱和酮的X射线晶体结构。

Fused full pi-conjugated systemss containing seven-membered ring are molecules of both theoretical and experimental interest due to their unique electronic structures, and various kinds of such compounds have been prepared. However the reported synthetic methods generally suffered from tedious multistep procedures and low yields at the stage of construction of the unsaturated seven-membered ring. We pay our attention to electrophilic nature of tropylium ion, and developed two facile synthetic methods of the compounds containing conjugated seven-membered ring. Our synthetic stratery was to use commercially available 1,3,5-cycloheptatriene as the seven-membered unit.1) The facile and novel synthesis of fused full conjugated cyclic compounds containing tropylium ion by an intramolecular Friedel-Crafts type reaction of o-aryl-, and o-heteroaryl-tropyliobenzenes. Cyclohepta [a] thienonaphthalenylium ions and cyclohepta [a] furonaphthalenylium ion which are the isoelectronic cations of triphenylene, and cyclohepta [a] benzofuro [c] naphthalenylium ions, cyclohepta [alpha] benzothieno [c] naphthalenylium ions and cyclohepta [a] indoro [c] naphthalenylium ion which are the isoelectronic carbocations of the potent carcinogenic benzo [g] chrysene, were obtained in reasonable yields.2) The facile and novel synthesis of heteroaromatic fused azurene derivatives.beta- (10-Benz [a] -azulenyl) -a, b-unsaturated ketone and beta- (9-azuleno [1,2-b] thienyl) -alpha, beta-unsaturated ketones were obtained from omicron- [2-furyl] tropyliobenzenes and 1-tropylio-2- [2-furyl] thiophenes, respectively, in reasonable yields. The mechanism involving a novel ring-cyclization by intramolecular attack of the tropylium ion to the 2-position of the furan ring is postulated. X-ray crystal structure of two of beta- (9-azuleno [1,2-b] thienyl) -alpha, beta-unsaturated ketones have been determined.