Consecutively fused single‐, double‐, and triple‐expanded helicenes
Consecutively fused single‐, double‐, and triple‐expanded helicenes
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DOI：
10.1002/ntls.20210047
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发表时间：
2022-03
期刊：
影响因子：
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通讯作者：
Wei Zheng;T. Ikai;Kosuke Oki;E. Yashima
中科院分区：
文献类型：
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作者：
Wei Zheng;T. Ikai;Kosuke Oki;E. Yashima
摘要我们报道了无缺陷的C形单链和S形和M形双链和三链连续熔融的同手性螺旋烯(全右手（P)或全左手(M)）的定量、化学选择性和非对构特异性形成，其中两个和三个膨胀的螺旋烯亚基分别以螺旋缠绕方式完全熔融在一起。通过三氟乙酸促进的分子内多步级联炔苄基环化前体，由于轴向手性的原因，形成了由大量复杂的动态立体异构体组成的环化前体。经手性色谱分离得到的外消旋膨化螺旋烯均为对映体，具有较强的圆二色性和圆偏振发光（CPL），吸收和发光不对称系数分别高达1.5 × 10−2和0.94 × 10−2。此外，三膨胀螺旋烯在所有CPL -活性碳-杂螺旋烯和-螺旋烯中显示出最高的CPL亮度（255 M−1·cm−1）。螺旋反转势垒随着螺旋烯亚基数量的增加而显著增加，即使在80°C下，三倍膨胀螺旋烯的外消旋化也被完全抑制，提供了具有静态螺旋手性的光学活性膨胀螺旋烯的第一个例子。无缺陷合成了分别具有C型、S型和M型全共轭螺旋阶梯结构的单、双、三膨胀螺旋烯。定量和化学选择性酸催化非对映特异性多步级联环化。构型稳定的纯展开螺旋螺旋的圆偏振发光。
AbstractWe report the quantitative, chemoselective, and diastereospecific formation of the defect‐free C‐shaped single and S‐ and M‐shaped consecutively fused double‐ and triple‐expanded homochiral helicenes (all‐right (P) or all‐left (M) handed), in which two and three expanded helicene subunits were exclusively fused together in a helically winding manner, respectively, through the trifluoroacetic acid‐promoted intramolecular multistep cascade alkyne benzannulations of anthracene‐based cyclization precursors composed of a large number of complicated dynamic stereoisomers due to axial chirality. The resulting racemic expanded helicenes were all separated into enantiomers by chiral chromatography and showed intense circular dichroism and circularly polarized luminescence (CPL) with the absorption and luminescence dissymmetry factors of up to 1.5 × 10−2and 0.94 × 10−2, respectively. Moreover, the triple‐expanded helicene showed the highest CPL brightness (255 M−1·cm−1) among all the reported CPL‐active carbo‐ and heterohelicenes and ‐helicenoids. The helicity inversion barriers remarkably increased with the increasing number of incorporated helicene subunits, and the racemization of the triple‐expanded helicene was completely suppressed even at 80°C, providing the first example of an optically active expanded helicene with a static helical chirality.Key PointsDefect‐free synthesis of single‐, double‐, and triple‐expanded helicenes with C‐, S‐, and M‐shaped fully conjugated helical ladder structures, respectively.Quantitative and chemoselective acid‐catalyzed diastereospecific multistep cascade cyclizations.Circularly polarized luminescence of configurationally stable optically pure expanded helicenes.