Directed ruthenium-catalysed C-H functionalisation of heteroarenes, such as 2-phenylpyridineor 1-phenylpyrazole, has emerged as an efficient and environmentally benign alternative totraditional cross-coupling chemistry. Using readily available and inexpensive aryl halides, themechanisms of these transformations are beginning to be understood. However, there has beenno work completed towards understanding the different directing group power of thesesubstrates. Many of the literature examples consider only the behaviour of substrates with onefunctional group, and the behaviour of more densely functionalised substrates remainsunpredictable.In this work we have presented a quantitative reactivity scale of directing group power for aseries of ruthenium(II)-catalysed ortho-directed intermolecular C-H arylation reactions acrossa range of substrates. The scale of directing group power has been determined using sets ofcompetition reactions that were analysed by calibrated GC-FID. Using least squaresminimisation, relative reaction rates were obtained for each substrate delivering the firstquantifiable assessment of directing group power.These results have found that, in our series, 2-phenylpyridine >> 2-phenylpyrazole > Nmethyl-2-phenyl-imidazole > 2-phenyloxazoline >> N-(1-phenylethylidene)aniline. Theseresults cover a synthetically useful reactivity range of 10²and allow a quantitative predictionof site selectivity under the conditions examined.Additionally, we have presented initial experimental findings that support the intermolecularquantitative predictions within an intramolecular substrate. This sets the scene for predictionof regioselectivity in more densely functionalised molecules, on an inter- and intramolecularsetting.
| Date of Award | 12 Oct 2017 |
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| Original language | English |
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| Awarding Institution | - University Of Strathclyde
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