Palladium-Catalyzed Cascade Process Consisting of Isocyanide Insertion and Benzylic C(sp<sup>3</sup>)–H Activation: Concise Synthesis of Indole Derivatives
作者:Takeshi Nanjo、Chihiro Tsukano、Yoshiji Takemoto
DOI:10.1021/ol302035j
日期:2012.8.17
Synthesis of the indole skeleton was achieved using a Pd-catalyzed cascade process consisting of isocyanide insertion and benzylic C(sp3)–H activation. It was found that slow addition of isocyanide is effective for reducing the amount of catalyst needed and Ad2PnBu is a good ligand for C(sp3)–H activation. The construction of the tetracyclic carbazole skeleton was also achieved by a Pd-catalyzed domino
吲哚骨架的合成是通过Pd催化的级联过程完成的,该过程由异氰酸酯插入和苄基C(sp 3)–H活化组成。研究发现,缓慢添加异氰酸酯可有效减少所需催化剂的量,而Ad 2 P n Bu是C(sp 3)–H活化的良好配体。四环咔唑骨架的构建也通过掺有炔烃插入的Pd催化的多米诺反应来实现。
Alkanethiol-Mediated Cyclization of <i>o</i>-Alkynylisocyanobenzenes: Synthesis of Bis-Thiolated Indole Derivatives
the corresponding bis-thiolated indolederivatives. The advantages of the reaction include metal-free, room-temperature, mild reaction conditions and broad functional group compatibility. The reaction proceeds via nucleophilic addition of an alkanethiol to an isonitrile moiety, 5-exo cyclization, followed by nucleophilic addition of an alkanethiol to a 3-alkylidene indole intermediate. Density functional
Diverse 2-sulfonyl- and 2-thiocyanato-3-substituted quinolines were synthesized from o-alkynylisocyanobenzenes by nucleophilic addition of the respective sulfinate sodium salts and ammonium thiocyanate to the isocyanide moiety followed by cyclization. The salient features of the methodology include metal-free, ambient temperature and mild reaction conditions, ease of reagent handling, and broad functional
When a mixture of o-alkynylaryl isocyanides and organic dichalcogenides such as diselenides or ditellurides was irradiated with light of wavelength over 300 or 400 nm, the intramolecular cyclization of the isocyanides took place to afford the corresponding 2,4-bischalcogenated quinolines selectively. The photochemical cyclization of 2-(phenylethynyl)phenyl isocyanide could also proceed in the presence of hydrogen transfer reagents such as tris(trimethylsilyl)silane, tributylgermyl hydride, alkanethiols, and benzeneselenol, providing the corresponding 3-phenylquinoline as the result of 2,4-dihydrogenation.
When o-alkynylaryl isocyanides 1 are treated with triethylamine in chloroform, intramolecular chlorinating cyclization of the isocyanides takes place, affording the corresponding 2-chlorinated quinoline derivatives 2 in good to excellent yields, selectively. Bromoform can be also used for the brominating cyclization of 1. Furthermore, fluorinating and iodinating cyclization of o-alkynylaryl isocyanides has been attained by the selection of fluoride and iodide (ion) sources.