在六氟异丙醇[（CF）CHOH]中通过布朗斯特酸催化的环化芳构化反应合成螺旋烯。

Fujita Takeshi, Shoji Noriaki, Yoshikawa Nao, Ichikawa Junji

Division of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.

Beilstein J Org Chem. 2021 Feb 9;17:396-403. doi: 10.3762/bjoc.17.35. eCollection 2021.

A facile synthesis of carbo- and heterohelicenes was achieved via tandem cycloaromatization of bisacetal precursors, which were readily prepared through C-C bond formation by Suzuki-Miyaura coupling. This cyclization was efficiently realized by a catalytic amount of trifluoromethanesulfonic acid (TfOH) in a cation-stabilizing solvent, 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP), which readily allowed gram-scale syntheses of higher-order helicenes, double helical helicenes, and heterohelicenes.

通过双缩醛前体的串联环化反应，实现了碳螺旋烯和杂螺旋烯的简便合成，双缩醛前体可通过铃木-宫浦偶联反应形成C-C键轻松制备。在阳离子稳定溶剂1,1,1,3,3,3-六氟-2-丙醇（HFIP）中，催化量的三氟甲磺酸（TfOH）可有效实现这种环化反应，该反应能够轻松实现克级规模的高阶螺旋烯、双螺旋螺旋烯和杂螺旋烯的合成。