Co‐Condensation Reactions of Substituted Aromatic Compounds with Lithium Atoms at 77 K

Abstract

Lithium atoms were co‐condensed with +I‐substituted benzene derivatives like trimethyl(phenyl)silane and tert‐butylbenzene in the presence of THF at 77 K, which resulted in C−H bond activation, to produce the aryllithium compound as well as the coupling of the substituted phenyl radicals. Other +I‐substituted benzene derivatives like xylene and mesitylene failed to react with lithium atoms in the presence of THF. Oxygen and nitrogen donor substituted benzene derivatives (anisole, N,N‐dimethylaniline, and N,N‐dimethylbenzylamine) showed activation of the ortho C−H bond when co‐condensed with lithium atoms in the presence of THF. However, when thioanisole was co‐condensed with lithium atoms and THF, a C−S bond cleavage occurred instead. These results were interpreted with the aid of DFT calculations, which show π‐ and σ‐complexes between the lithium clusters and benzene derivatives as reactive intermediates. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Cocondensation Reactions of Five‐Membered Heterocycles with Lithium Atoms at 77 K

“…The first possibility is the coordination of the Li 2 cluster to the aromatic system to form a π-complex, and the second possibility is η 1 -coordination of the Li 2 cluster to the heteroatom in the ring. [12] When methyl groups are placed in the two ortho positions in the furan, a similar situation is found. The η 1 -complex is the more stable intermediate with a small energy difference of 2.7 kcal/mol from the π-complex.…”

“…[9,10,11] When a methoxy group was added to the aromatic hydrocarbons, activation was always found in an ortho position with respect to the methoxy group. [12] Thus methoxy groups can be considered as useful tools to activate the ortho position on hydrocarbon aromatic rings.…”

“…[12] The aim of this paper was to perform cocondensation reactions with furans, thiophenes, pyrroles and oxazole in order to find similarities to and differences from benzene derivatives.…”

Efficient homocoupling reactions of halide compounds catalyzed by manganese (II) chloride

“…[23] This compound was prepared from 1g and the catalytic system [24] This compound was prepared from 1h and the catalytic system [25] This compound was prepared from 1i and the catalytic system MnCl 2 -Mg to give the product as a white solid after column chromatography with hexane.…”

Cocondensation reactions of heterocyclic aromatic compounds with lithium, calcium and magnesium atoms at 77K

“…The work has been expanded to +I substituted (CMe 3 , SiMe 3 , o-and m-xylene) and donor substituted (OMe, NMe 2 , SMe) benzene derivatives [7] as well as five-membered heterocycles [8] and nitrogen-containing heterocycles [9]. In the case of anisole a selective C-H bond activation was found to occur in the absence of THF as well; its reaction mechanism was calculated in detail in a recent DFT study [10].…”