Addition of 1,3-dicarbonyl compounds to terminal alkynes catalyzed by a cationic cobalt(<scp>iii</scp>) complex
作者:Mohan Chandra Sau、Manish Bhattacharjee
DOI:10.1039/d0ra05923d
日期:——
The Nakamura reaction using a cationic cobalt(III) complex, [Cp*Co(CH3CN)3][SbF6]2 as the catalyst under neutral and aerobic conditions at 110 °C has been described. In solution, the complex is expected to lose a hemilabile acetonitrile ligand to produce a highly electron-deficient cobalt(III) center, and the Lewis acidic nature of the cobalt center has been exploited for the enolization of the dicarbonyl
已经描述了使用阳离子钴( III ) 配合物[Cp*Co(CH 3 CN) 3 ][SbF 6 ] 2作为催化剂在中性和有氧条件下在110 °C 下的Nakamura 反应。在溶液中,该配合物预计会失去半可溶的乙腈配体,从而产生高度缺电子的钴(III) 中心,并且钴中心的路易斯酸性已被用于二羰基化合物的烯醇化。1,3-二羰基化合物与炔烃反应得到相应的烯基衍生物。然而,苯乙炔及其衍生物与 β-酮酯反应得到相应的三联苯化合物。已经基于原位LCMS 测量提出了反应机制的细节。
Manganese-Catalyzed Construction of Tetrasubstituted Benzenes from 1,3-Dicarbonyl Compounds and Terminal Acetylenes
Treatment of beta-keto esters with terminal acetylenes in the presence of a catalytic amount of a manganese complex, MnBr(CO)(5), and molecular sieves, gave multisubstituted aromatic compounds in good to excellent yields. This reaction employs [2 + 2 + 2] cycloaddition of beta-keto esters and 2 equiv of terminal acetylenes with dehydration. In the case of a 1,3-diketone, the corresponding acetophenone derivative and its deacylated compound can be synthesized selectively.
Manganese-Catalyzed Benzene Synthesis by [2+2+2] Coupling of 1,3-Dicarbonyl Compound and Terminal Acetylene
Treatment of a mixture of a 1,3-dicarbonyl compound such as a beta-ketoester or 1,3-ketone and a terminal acetylene with a catalytic amount of MnBr(CO)(5) in heated toluene produces a benzene derivative by a [2+2+2] coupling reaction incorporating the enol part of the dicarbonyl compound and two moles of the acetylene. When the reaction was carried out using phenylacetylene derivatives, the reaction was completely regioselective, producing p-terphenyl compounds in good to excellent yield. Aliphatic terminal acetylenes also reacted readily but gave a mixture of regioisomers. The reaction features high atom economy, neutral conditions, and functional group tolerance, and will be useful for materials-oriented studies.