4282-45-5Relevant articles and documents
Intercepting palladacycles derived by C-H insertion. A mechanism-driven entry to heterocyclic tetraphenylenes
Masselot, David,Charmant, Jonathan P. H.,Gallagher, Timothy
, p. 694 - 695 (2006)
Mechanistic support for the intermediacy of a palladacycle, which has been implicated in the crossover Heck reaction, has been obtained by intercepting this species using biphenylene. This leads to the formation of heterocyclic tetraphenylene derivatives. Three examples of this process are reported, and in two cases, the product structures have been confirmed by X-ray crystallographic analysis. Copyright
Quantifying Through-Space Substituent Effects
Adam, Catherine,Burns, Rebecca J.,Cockroft, Scott L.,Mati, Ioulia K.,Muchowska, Kamila B.
supporting information, p. 16717 - 16724 (2020/07/24)
The description of substituents as electron donating or withdrawing leads to a perceived dominance of through-bond influences. The situation is compounded by the challenge of separating through-bond and through-space contributions. Here, we probe the experimental significance of through-space substituent effects in molecular interactions and reaction kinetics. Conformational equilibrium constants were transposed onto the Hammett substituent constant scale revealing dominant through-space substituent effects that cannot be described in classic terms. For example, NO2 groups positioned over a biaryl bond exhibited similar influences as resonant electron donors. Meanwhile, the electro-enhancing influence of OMe/OH groups could be switched off or inverted by conformational twisting. 267 conformational equilibrium constants measured across eleven solvents were found to be better predictors of reaction kinetics than calculated electrostatic potentials, suggesting utility in other contexts and for benchmarking theoretical solvation models.
Photoarylation of Pyridines Using Aryldiazonium Salts and Visible Light: An EDA Approach
Bartolomeu, Aloisio De A.,Brocksom, Timothy J.,De Oliveira, Kleber T.,No?l, Timothy,Silva, Rodrigo C.
, (2019/08/26)
A metal-free methodology for the photoarylation of pyridines, in water, is described giving 2 and 4-arylated-pyridines in yields up to 96percent. The scope of the aryldiazonium salts is presented showing important results depending on the nature and position of the substituent group in the diazonium salt, that is, electron-donating or electron-withdrawing in the ortho, meta, or para positions. Further heteroaromatics were also successfully photoarylated. Mechanistic studies and comparison between our methodology and similar metal-catalyzed procedures are presented, suggesting the occurrence of a visible-light EDA complex which generates the aryl radical with no need for an additional photocatalyst.
