ICMMO, UMR CNRS 8182, Université Paris-Sud 11, 91405 Orsay cedex, France.
J Org Chem. 2010 Dec 17;75(24):8435-49. doi: 10.1021/jo101709n. Epub 2010 Nov 17.
Under noble (Au, Pt, Ru) and group 13 (Ga, In) metals catalysis, 1,6-arenynes rearrange to give 1,2-dihydronaphthalenes in a high yielding, regiocontrolled fashion. When the reaction is carried out in the presence of electron-rich arenes (anisole, phenol, indole derivatives), Friedel-Crafts addition may follow the cycloisomerization step. Only GaX(3) salts proved able to catalyze these two C-C bond formation events. This specificity of gallium has been exploited for the synthesis of valuable polycyclic compounds that would be very difficult to prepare otherwise. For instance, tetrahydroisoquinolines and tetrahydrobenzoazepines have been obtained by selective 6-exo-dig or 7-endo-dig cyclization of N-tethered 1,6-arenynes. DFT calculations were carried out to shed light on the mechanism and provide a rationale for this regiodivergency. Computations also reveal the fundamental role of the tether in the stabilization of carbocationic species. Differential reactivities of other types of substrates in gallium- and gold-catalyzed cascades are also exposed, showing that the two approaches are complementary. In particular, bimolecular Friedel-Crafts additions are facilitated under gallium catalysis.
在贵金属（金、铂、钌）和第 13 族金属（镓、铟）催化下，1,6-芳炔重排以高产率、区域选择性方式得到 1,2-二氢萘。当反应在富电子芳环（苯甲醚、苯酚、吲哚衍生物）存在下进行时，傅克加成可能会紧随环化异构化步骤。只有 GaX(3)盐被证明能够催化这两个 C-C 键形成反应。镓的这种特异性已被用于合成非常难以制备的有价值的多环化合物。例如，通过选择性的 6-endo-dig 或 7-endo-dig 环化 N-键合的 1,6-芳炔，可以得到四氢异喹啉和四氢苯并氮杂卓。通过密度泛函理论（DFT）计算阐明了反应机理，并为这种区域多样性提供了理论依据。计算还揭示了连接基团在稳定碳阳离子物种中的基本作用。还揭示了其他类型底物在镓和金催化级联反应中的不同反应活性，表明这两种方法是互补的。特别是，双分子傅克加成在镓催化下更容易进行。
