Cine Substitution of Arenes Using the Aryl Carbamate as a Removable Directing Group
摘要:
An efficient and controlled means to achieve a rare cine substitution of arenes is reported. The methodology relies on the strategic use of aryl O-carbamates as readily removable directing groups for arene functionallzation. The removal of aryl carbamates is achieved by employing an airstable Ni(II) precatalyst, along with an inexpensive reducing agent, to give synthetically useful yields across a range of substrates. The net cine substitution process offers a new strategy for analogue synthesis, which complements the well-established logic for achieving arene functionalization by ipso substitution.
Herein we describe an iron-catalyzed borylation of alkenyl and arylcarbamatesthrough the activation of a C–O bond. This protocol exhibits high efficiency, a broad substrate scope, and the late-stage borylation of biorelevant compounds, thus providing potential applications in medicinal chemistry. Moreover, this method enables orthogonal transformations of phenol derivatives and also offers good opportunities
在本文中,我们描述了通过C-O键的活化,铁催化的烯基和芳基氨基甲酸酯的硼酸酯化反应。该方案显示出高效率,广泛的底物范围以及生物相关化合物的后期硼化,因此在药物化学中提供了潜在的应用。而且,该方法能够使酚衍生物进行正交转化,并且还为合成多取代的芳烃提供了良好的机会。初步的机理研究表明,通过自由基途径的Fe II / Fe III催化循环可能与反应有关。
Revisitation of Organoaluminum Reagents Affords a Versatile Protocol for C–X (X = N, O, F) Bond-Cleavage Cross-Coupling: A Systematic Study
A revisit of organoaluminumreagents for cross-coupling reactions has opened up several types of C–C bond formation protocols through cleavage of phenolic/alcoholic C–O and C–F and ammonium C–N bonds. Catalyzed by the commercially available NiCl2(PCy3)2 catalyst, these reactions proceed smoothly with a wide range of substrates and broad functional group compatibility, providing a versatile methodology
Aryl carbamates were employed in the nickel-catalyzed monoarylation of ammonia. The applied, well-defined single-component nickel(II) precatalyst contains a Josiphos ligand, is air-stable, and operates without any ancillary reductant. This catalyst system also promotes the amination of aryl carbamates with ammonium sulfate as well as with hydrochloride salts of primary alkylamines. Their easy preparation
氨基甲酸芳基酯用于氨的镍催化单芳基化。应用的、定义明确的单组分镍 (II) 预催化剂包含 Josiphos 配体,在空气中稳定,并且无需任何辅助还原剂即可运行。该催化剂体系还促进了氨基甲酸芳基酯与硫酸铵以及伯烷基胺的盐酸盐的胺化。它们的容易制备、稳健性和导向基团能力使氨基甲酸芳基酯成为特别有吸引力的合成中间体。
Suzuki−Miyaura Cross-Coupling of Aryl Carbamates and Sulfamates: Experimental and Computational Studies
作者:Kyle W. Quasdorf、Aurora Antoft-Finch、Peng Liu、Amanda L. Silberstein、Anna Komaromi、Tom Blackburn、Stephen D. Ramgren、K. N. Houk、Victor Snieckus、Neil K. Garg
DOI:10.1021/ja200398c
日期:2011.4.27
The first Suzuki-Miyaura cross-coupling reactions of the synthetically versatile aryl O-carbamate and O-sulfamate groups are described. The transformations utilize the inexpensive, bench-stable catalyst NiCl2(PCy3)(2) to furnish biaryls in good to excellent yields. A broad scope for this methodology has been demonstrated. Substrates with electron-donating and electron-withdrawing groups are tolerated, in addition to those that possess ortho substituents. Furthermore, heteroaryl substrates may be employed as coupling partners. A computational study providing the full catalytic cycles for these cross-coupling reactions is described. The oxidative addition with carbamates or sulfamates occurs via a five-centered transition state, resulting in the exclusive cleavage of the aryl C-O bond. Water is found to stabilize the Ni-carbamate catalyst resting state, which thus provides rationalization of the relative decreased rate of coupling of carbamates. Several synthetic applications are presented to showcase the utility of the methodology in the synthesis of polysubstituted aromatic compounds of natural product and bioactive molecule interest.
Suzuki−Miyaura Coupling of Aryl Carbamates, Carbonates, and Sulfamates
作者:Kyle W. Quasdorf、Michelle Riener、Krastina V. Petrova、Neil K. Garg
DOI:10.1021/ja906477r
日期:2009.12.16
The first Suzuki-Miyaura cross-couplings of carbamates, carbonates, and sulfamates is described. The method provides a powerful means of using simple derivatives of phenol as precursors to polysubstituted aromatic compounds, as exemplified by a concise synthesis of the anti-inflammatory drug flurbiprofen.