Metalations utilizing aryllithiums; ortho-functionalization of p-bromoanisole (pBrA)
摘要:
An ortho-metalation protocol has been developed, which permits the survival of a bromine substituent in p-bromoanisole. Eight derivatives of the generated ortho-lithiated intermediate have been prepared. A neglected metalation concept is being explored here: one which proposes that minimizing the pK(a) difference between the aryl substrate and the conjugate acid of the metalating agent will lead to a regiospecific and selective metalation process. Published by Elsevier Ltd.
Two 2-[bis(pentafluorophenyl)boryl]-N,N-dialkylanilines reported here exemplify a new class of intramolecular frustrated B/N Lewis pairs. A structure closely related to this class structure was synthesized in 2003 by Piers et al. but was unable to activate H2. The new aminoboranes can activate hydrogen at near ambient conditions; besides, one of them can hydrogenate imines and enamines in a catalytic fashion demonstrating the validity of the original Piersâ approach to hydrogen activation with ansa-aminoboranes.
Efficient Pd‐Catalyzed Direct Coupling of Aryl Chlorides with Alkyllithium Reagents
作者:Thorsten Scherpf、Henning Steinert、Angela Großjohann、Katharina Dilchert、Jens Tappen、Ilja Rodstein、Viktoria H. Gessner
DOI:10.1002/anie.202008866
日期:2020.11.9
organometallic reagents and frequently used in difficult metallation reactions. However, their direct use in the formation of C−C bonds is less established. Although remarkable advances in the coupling of aryllithium compounds have been achieved, Csp2−Csp3 coupling reactions are very limited. Herein, we report the first general protocol for the coupling or aryl chlorides with alkyllithiumreagents. Palladium
作者:Dominic R. Willcox、Daniel M. De Rosa、Jack Howley、Abigail Levy、Alan Steven、Gary S. Nichol、Carole A. Morrison、Michael J. Cowley、Stephen P. Thomas
DOI:10.1002/anie.202106216
日期:2021.9.13
reactivity at the aluminium hydride centre, switching off hydroalumination and instead enabling selective reactions at the alkyne C−H σ-bond. Chemoselective C−H borylation was observed across a series of aryl- and alkyl-substituted alkynes (21 examples). On the basis of kinetic and density functional theory studies, a mechanism in which C−H borylation proceeds by σ-bondmetathesis between pinacolborane (HBpin)
Influence of the catalyst structure in the cycloaddition of isocyanates to oxiranes promoted by tetraarylstibonium cations
作者:Mengxi Yang、Nilanjana Pati、Guillaume Bélanger-Chabot、Masato Hirai、François P. Gabbaï
DOI:10.1039/c8dt00702k
日期:——
been evaluated as catalysts for the cycloaddition of oxiranes and isocyanates under mild conditions. While all stibonium cations favor the 3,4-oxazolidinone products, the reactivities of 5+ and 6+ are hindered by the ancillary amino donor which quenches the Lewis acidity of the antimony center. A comparison of the other stibonium cations shows that 4+ is the most selective catalyst.
作者:Ramkumar Kannan、Raju Chambenahalli、Sandeep Kumar、Athul Krishna、Alex P. Andrews、Eluvathingal D. Jemmis、Ajay Venugopal
DOI:10.1039/c9cc08272g
日期:——
In search of stable, yet reactive aluminum Lewis acids, we have isolated an organoaluminum cation, [(Me2NC6H4)2Al(C4H8O)2]+, coordinated with two labile tetrahydrofuran ligands. Its catalytic performance in aldehyde dimerization reveals turn-over frequencies reaching up to 6000 h-1, exceeding that of the reported main group catalysts. The cation is further demonstrated to catalyze hydroelementation