REGIOSELECTIVITY IN THE PHOTOCYCLIZATION OF STILBENES

这项建议的目标是开发 紫外光照射下的光环化反应 邻甲氧基二苯乙烯在没有溶解氧的情况下得到4a-甲氧基-4a， 4B-二氢菲作为过渡中间体，随后可以 经过甲醇的消除，得到菲。除了几个人 由其他人报道的这种消除光环化的例子 1974年，工人的这种反应在很大程度上仍然被忽视。研究 将与母体邻甲氧基二苯乙烯进行最佳建立 反应条件；特别是，将检验这一假设 消除光环化反应在酸化甲醇中进行得比 在环己烷中也有。将对这一方案的可行性进行研究。 反应是克服区域化学问题的一种方法，有时 限制众所周知的氧化光环化反应的合成价值 方法。例如，间位取代的氧化光环化反应 二苯乙烯类化合物产生2-和4-取代菲的混合物，通常与 几乎没有地区选择性。的消除光环化反应 将携带2-甲氧基-5-甲基二苯乙烯和2-甲氧基-3-甲基二苯乙烯 来检验这样的假设，即这些反应会产生个体 2-甲基菲和4-甲基菲的样品。 2-苯基萘的氧化光环化反应表现出较高的活性 区域选择性，几乎只给出苯并[c]菲； 区域异构体苯并[a]并[a]菲仅在微量中生成。为 类似的原因，二苯并[a，j]菲和二苯并[a，h]菲 系统也不能通过氧化光环化来获得。它是 提议尝试提供合成苯并[a]菲的途径， 二苯并[a，j]-菲和二苯并[a，h]菲体系 3-甲氧基-2-苯基萘的消除光环化反应， 2，4-二甲氧基-1，5-二苯基苯和2，5-二甲氧基-1，4-二苯基苯， 分别进行了分析。 这些拟议的实验尝试开发了 消除光环化方法主要集中在最简单的分子上 示例，但最终目标是将这些示例视为原型 为未来该方法在多取代体系中的应用奠定了基础。这个 多核芳香族体系合成能力的扩展 在这里考虑的类型应该具有未来的重要性 与健康相关的研究，因为广泛发生的 与菲有关的生理活性天然产物，以及 苯并蒽类化合物的致癌性。

The objective of this proposal is to develop the synthetic potential of the photocyclization reaction in which the ultraviolet irradiation of o-methoxystilbenes in the absence of dissolved oxygen gives 4a-methoxy-4a, 4b-dihydrophenanthrenes as transient intermediates that subsequently can undergo elimination of methanol to give phenanthrenes. Except for a few examples of this eliminative photocyclization that were reported by other workers in 1974, this reaction has remained largely overlooked. Studies will be carried out with the parent o-methoxystilbene to establish optimum reaction conditions; in particular, the hypothesis will be tested that this eliminative photocyclization will proceed better in acidified methanol than it has in cyclohexane. Studies will be undertaken of the viability of this reaction as a method to overcome the regiochemical problems that sometimes limit the synthetic value of the well-known oxidative photocyclization method. For example, oxidative photocyclizations of meta-substituted stilbenes give mixtures of 2- and 4-substituted phenanthrenes, often with almost no regioselectivity. The eliminative photocyclizations of 2-methoxy-5-methylstilbene and 2-methoxy-3-methylstilbene will be carried out to test the hypothesis that these reactions will produce individual samples of 2- and 4-methylphenanthrene, respectively. Oxidative photocyclizations of 2-styrylnaphthalenes exhibit high regioselectivity, giving almost exclusively benzo[c]phenanthrenes; the regioisomeric benz[a]anthracenes are formed only in trace amounts. For similar reasons, the dibenz[a,j]anthracene and dibenz[a,h]anthracene systems also are not available by oxidative photocyclization. It is proposed to try to provide synthetic access to the benz[a]anthracene, dibenz[a,j]-anthracene, and dibenz[a,h]anthracene systems by carrying out eliminative photocyclizations of 3-methoxy-2-styrylnaphthalene, 2,4-dimethoxy-1,5-distyrylbenzene, and 2,5-dimethoxy-1,4-distyrylbenzene, respectively. These proposed experimental attempts to develop the synthetic utility of the eliminative photocyclization method focus on the simplest molecular examples, but the ultimate aim is to consider these examples as prototypes for future applications of the method to multi-substituted systems. The expansion of the capabilities for synthesizing polynuclear aromatic systems of the type considered here should have future importance for health-related studies because of the widespread occurrence of physiologically active natural products related to phenanthrenes, and the carcinogenicity of benzanthracenes.