Both syn- and anti-[2+2] heterodimers (1 and 2)
of methyl phenanthrene-9-carboxylate (9-MP) and benzene were synthesized from
9-MP and cyclohexa-1,4-diene. Upon irradiation of 9-MP and excess methyl orthoformate
of cis-cyclohexa-3,5-diene-1,2-diol followed by hydrolysis, the syn-[2+2]
cycloadduct and also four cyclodimers of 9-MP were produced. Triplet-sensitized
photocycloaddition followed by hydrolysis provided the anti-[2+2]
cycloadduct. Dehydroxylation of the cycloadducts under mild conditions gave 1 and 2.
In contrast to the previous reports on [2+2] dibenzenes and [2+2] heterodimers
of acenaphthylenes and benzene, kinetic analysis of the thermolyses of 1 and 2
indicated that 1 was kinetically
less stable than 2. Photodissociation
of 1 and 2
were found to be adiabatic with efficiencies of 0.33 and 0.39. An explanation
is provided for their thermoreversion and photoreversion.
由 9-MP 和
环己烯-1,4-二烯合成了
菲-9-
羧酸甲酯(9-MP)和苯的合[2+2]异二聚体(1 和 2)。将 9-MP 和过量的顺式-环己-3,5-二烯-1,2
-二醇的原
甲酸甲酯进行辐照,然后进行
水解,生成了 9-MP 的合成[2+2]环加载物和四个环二聚体。三重敏化光环加成后再
水解,可得到反[2+2]环加合物。与之前有关[2+2] 二苯以及
苊烯和苯的[2+2] 异二聚体的报道不同,对 1 和 2 的热解动力学分析表明,1 在动力学上不如 2 稳定。研究发现,1 和 2 的光解是绝热的,效率分别为 0.33 和 0.39。这为它们的热转化和光转化提供了解释。