<i>o</i>‑Quinones Derived from Tribenzotriquinacenes: Functionalization of Inner Bay Positions and Use for Single-Wing Extensions

Through a surprisingly nonregioselective oxidation process, the reaction of two analogous 2-hydroxy-substituted tribenzotriquinacenes (TBTQs) 8a/8b by o-iodoxybenzoic acid was found to afford the corresponding Cs- and C1-symmetrical TBTQ-o-quinones 6a/6b and 7a/7b, respectively, in 1:1 ratio and excellent combined yields. This finding represents the first example of direct introduction of a functional group into a sterically hindered, inner bay-positions of a parent TBTQ skeleton. In contrast, the analogous reaction with 1-hydroxy-TBTQ 15 failed to produce the desired o-quinone 7a. After reduction of the quinones 6a and 7a to the corresponding catechols 17 and 23, electrophilic aromatic substitution could also be realized at the activated inner bay-position(s) to afford several tri- and tetrafunctionalized TBTQ compounds 18, 21, and 25. The Cs-symmetrical o-quinone 6a was converted into further single-wing extended derivatives such as TBTQ-based phenazines 27a–f, through condensation reactions, and to benzodioxine derivative 32 by Diels–Alder reaction with tetracyclone. The novel TBTQ-quinones and the corresponding TBTQ-catechols offer a variety of new accesses to single-wing-extended and -functionalized TBTQ derivatives.通过一种意外的非区域选择性氧化过程，研究发现，两种结构相似的2-羟基取代三苯并三喹烷（tribenzotriquinacenes, TBTQs）8a/8b与邻碘酰苯甲酸（o-iodoxybenzoic acid）发生反应，可分别得到对应的C_s对称TBTQ邻醌6a/6b与C1对称TBTQ邻醌7a/7b，产物比例为1:1，总收率优异。该发现首次实现了在母型TBTQ骨架的位阻较大内侧湾位直接引入官能团。与之相对，以1-羟基-TBTQ 15进行的类似反应未能得到目标邻醌7a。将邻醌6a与7a还原为对应的儿茶酚17与23后，可在活化的内侧湾位发生亲电芳香取代反应，得到多种三官能团化与四官能团化的TBTQ化合物18、21与25。C_s对称的邻醌6a可通过缩合反应进一步转化为单翼扩展衍生物，例如基于TBTQ的吩嗪类化合物27a–f；还可与四苯基环戊二烯酮（tetracyclone）发生狄尔斯-阿尔德反应（Diels–Alder reaction），得到苯并二噁英衍生物32。新型TBTQ醌类化合物及其对应的TBTQ儿茶酚类衍生物，为制备单翼扩展及官能团化的TBTQ衍生物提供了多种全新的合成路径。