AA-STARR: Aromatic Amine Synthesis by Tapping Aminium Radical Reactivity

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Aromatic amines are amongst the most important chemical motifs, featuring in functional molecules such as colourants, pharmaceutical drugs and agrochemicals. Indeed, the foundation of the modern chemical industry was driven in large part by the development of new dyestuffs based on aromatic amines in the 1850s. Despite the significance of aryl amines, methods for their production can still involve wasteful multi-step processes with noxious waste streams. More modern methods have been developed such as the so-called Buchwald-Hartwig coupling, but these require the use of pre-functionalised substrates (which carry their own waste inventory) and catalysts based upon the scarce precious metal palladium. In this work, we will develop methods to directly aminate aromatic rings using simple and cheap reagents in conjunction with light sources (ultra-violet and visible). The reactions exploit active species known as aminium radicals. Reactions of aminium radicals have been known for over 100 years, but they remain underexploited. We have recently developed ways to harness these reactive species to give highly productive amination of aromatics. Further, the reactivity allows us to access unusual molecular structures which will find applications in drug discovery and the preparation of fluorescent materials.Our objectives are to (i) create a suite of conditions to achieve the amination reactions; (ii) to demonstrate this in the creation of a wide range of novel molecules with diverse structures; (iii) develop a new variant in which the aromatic ring is 'destroyed' in the process, allowing access to very different products from the same type of starting materials. We will demonstrate non-academic impact of our work by making novel molecular 'building blocks' available to buy (through a project partner), and by creating a unique library of small molecules known as fragments which can be used for screening programmes in drug discovery.