NOZON - Development of a Novel Photochemical Strategy for the “Ozonolysis-like” Cleavage of Aromatics Using Photoexcited Nitroarenes

• Applicant: Professor Dr. Daniele Leonori
• Subject Area: Organic Molecular Chemistry - Synthesis and Characterisation
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 545531108

Aromatics are feedstocks obtained from petroleum mass of integral relevance to the preparation of high-value materials. As an example, the European production of benzene, toluene and xylenes amounts to >12million tons per year. The vast majority of reactions run on these species retain the aromatic core, either through introduction of new substituents or manipulation of pre-existing functionalities. A different and highly underdeveloped approach would be to deconstruct the aromatic skeleton while simultaneously introducing useful functionality handles. In particular, the possibility to run ozonolysis on aromatics would convert these stable species into carbonyl-rich intermediates which can be easily converted into high-value materials. Achieving this is however very difficult because ozone has higher reactivity towards the cleavage products than the starting aromatics and this causes uncontrolled side- and decomposition reactions. Furthermore, the use of ozone raises many toxicity and safety concerns causing it to be often a banned reagent in both academia and industry. The invention of a novel strategy able to oxidatively deconstruct aromatics in a controllable and selective manner, without using ozone, would be of strategic importance to streamline the preparation of functional building blocks. The overarching aim of this joint French–German proposal is to develop the first general oxidative cleavage of aromatics. We aim to use simple nitroarenes, a large class of feedstocks produced annually on multi ton-scale, as photoactive oxidants in combination with visible-light. This strategy will explore the ability of these species to undergo photoexcitation to the triplet state and engage in novel addition reactions to aromatics. This reactivity blueprint will eventually lead to the cleavage of one specific aromatic position over others without additional oxidation. In this way, we will provide fundamentally new tactics for the synthesis O-containing fragments currently difficult to prepare but highly sought after by pharmaceutical and agrochemical discovery programs. The primary scientific objectives involved are: (1) To develop the first approach where nitroarenes and visible-light are used to perform the oxidative cleavage of aromatics. (2) To apply this reactivity to the oxidation of several types of aromatics and to fully evaluate the scope of the process. (3) To understand the key mechanistic aspects of this photochemical activation using several spectroscopic, experimental and computational techniques. (4) To scale-up the process using flow technologies (ideally >25g scale). (5) To demonstrate the potential of the oxidative cleavage process for the deconstruction and diversification of ‘high-value molecules’. Overall, this proposal aims to introduce a fundamentally novel approach where visible-light and nitro-aromatics are used for the conversion of feedstock materials to those to academia as well as the bulk- and fine-chemical sectors.

• DFG Programme: Research Grants
• International Connection: France
• Partner Organisation: Agence Nationale de la Recherche / The French National Research Agency
• Cooperation Partner: Professor Thomas Poisson