Relative Basicities of ortho-, meta-, and para-Substituted Aryllithiums
摘要:
The relative basicities of aryllithiums bearing methoxy, chlorine, fluorine, trifluoromethyl and trifluoromethoxy substituents at the ortho, meta, and para positions have been assessed. To this end, two aryllithiums of comparable basicity were equilibrated together with the corresponding bromo- or iodoarenes in a 1: 2 mixture of pentanes with tetrahydrofuran at -50, -75, or -100 degrees C. The "basicity" (protodelithiation) increments Delta Delta G derived from the equilibrium constants are linearly correlated with the relative protonation enthalpies of the corresponding aryl anions in the gas phase. However, the correlation factor proves to be position-dependent. Compared with "naked" aryl anions, the basicity of aryllithiums mirrors the effects of ortho, meta, and para substituents to the extent of 36%, 30%, and 25%, respectively.
作者:Jorn de Jong、Dorus Heijnen、Hugo Helbert、Ben L. Feringa
DOI:10.1039/c8cc08444k
日期:——
followed by the Buchwald–Hartwigamination with in situ released lithium amides is presented. In this work amides are used as masked ketones, revealed by the addition of organolithium reagents which generates a lithium amide, suitable for subsequent Buchwald–Hartwig coupling in the presence of a palladium catalyst. This methodology allows for rapid, efficient and atom economic synthesis of aminoarylketones
Cross-Coupling Knows No Limits: Assessing the Synthetic Potential of the Palladium-Catalysed Cross-Coupling of Organolithiums
作者:James D. Firth、Peter O'Brien
DOI:10.1002/cctc.201402886
日期:2015.2
Organolithiums have passed the test! Previously considered too reactive and unstable, organolithiums have been tamed and can now participate successfully in palladium‐catalysed cross‐coupling with aryl/vinyl bromides and triflates.
2-bis(diphenylphosphino)benzene), substituents of increasing van der Waals volumes have been introduced into the ortho- or meta-positions of the platinum-bonded phenyl rings in order to influence the relative orientations of these rings with espect to the plane defined by the four valences of the central platinum. The consequences of the different conformations on the photochemical elimination of the biphenyl