ORGN 510 |
| The regioselective coupling of polyhaloheteroaromatics is an attractive route to differentially substituted heteroaromatics. Such an approach requires two main features: a method to predict the order/site of coupling and, ideally, reaction conditions that afford regioselective couplings. In terms of a predictive guide, we have developed a method based upon the 1H NMR chemical shift values of the parent non-halogenated aromatic systems, which enables the accurate prediction for polyhaloheteroaromatics studied in the literature as well as new systems from these labs. Further, two sets of experimental conditions have been discovered that enable regioselective couplings. One, using phosphine-modified palladium(0), works for compounds which are capable of serving as ligands on palladium (such as pyridine), while the second, using phosphine-free palladium, works for compounds which are not capable of serving as ligands. This combination has enabled us to achieve high levels of regioselectivity in the Suzuki coupling of a variety of polyhaloheteroaromatics.
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Heterocycles, Aromatics, Metal-Mediated Reactions and Syntheses, Materials, Devices, and Switches
8:00 PM-10:00 PM, Wednesday, 29 March 2006 Georgia World Congress Center -- Ex. Hall B4, Poster
Sci-Mix
Division of Organic Chemistry |
