A quantitative scale for directing group power in ruthenium(II)-catalysed ortho-directed C-H arylation reactions

  • Jamie McIntyre

Student thesis: Master's Thesis

Abstract

Directed ruthenium-catalysed C-H functionalisation of heteroarenes, such as 2-phenylpyridine or 1-phenylpyrazole, has emerged as an efficient and environmentally benign alternative to traditional cross-coupling chemistry. Using readily available and inexpensive aryl halides, the mechanisms of these transformations are beginning to be understood. However, there has been no work completed towards understanding the different directing group power of these substrates. Many of the literature examples consider only the behaviour of substrates with one functional group, and the behaviour of more densely functionalised substrates remains unpredictable. In this work we have presented a quantitative reactivity scale of directing group power for a series of ruthenium(II)-catalysed ortho-directed intermolecular C-H arylation reactions across a range of substrates. The scale of directing group power has been determined using sets of competition reactions that were analysed by calibrated GC-FID. Using least squares minimisation, relative reaction rates were obtained for each substrate delivering the first quantifiable 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. These results cover a synthetically useful reactivity range of 10² and allow a quantitative prediction of site selectivity under the conditions examined. Additionally, we have presented initial experimental findings that support the intermolecular quantitative predictions within an intramolecular substrate. This sets the scene for prediction of regioselectivity in more densely functionalised molecules, on an inter- and intramolecular setting.
Date of Award12 Oct 2017
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SupervisorDavid Nelson (Supervisor) & John Murphy (Supervisor)

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