Periodic Reporting for period 1 - DCMeta (Dual Catalysis for Meta Functionalisation under Mild Conditions)
Reporting period: 2019-02-01 to 2021-01-31
DCMeta is a catalysis project that has examined the role of visible light in activating metal catalysts for new chemical transformations.
The use of high energy UV light to enable chemical reactions has a long history in organic chemistry, enabling a large number of chemical reactions to proceed that are not feasible under any other method. The high energy implicit in UV photochemistry, however, along with attendant issues of specialised equipment and difficulties in scale-up, have hindered wider exploitation in industry for the synthesis of valuable molecules. Recent developments using visible light have created an exciting alternative, where simple light sources can be used in conjunction with a catalyst to enable new chemical reactivity.
The synthesis of new molecules under sustainable conditions has enormous importance in our society: DNA, sugars, proteins, the molecules of nature, drugs, insecticides and vitamins represent just some of the classes of molecule essential to the way we live our lives. As a result, the discovery of new and improved ways to synthesise new and improved molecules is at the forefront of modern chemistry research. The use of metal catalysis and photochemistry offers substantial improvements to both the synthesis of existing molecules and the discovery of new ones, which can have wide application in medicine, engineering and agriculture.
The overall objective is to harness visible light to control the behaviour of metal catalysts in chemical reactions.
The use of high energy UV light to enable chemical reactions has a long history in organic chemistry, enabling a large number of chemical reactions to proceed that are not feasible under any other method. The high energy implicit in UV photochemistry, however, along with attendant issues of specialised equipment and difficulties in scale-up, have hindered wider exploitation in industry for the synthesis of valuable molecules. Recent developments using visible light have created an exciting alternative, where simple light sources can be used in conjunction with a catalyst to enable new chemical reactivity.
The synthesis of new molecules under sustainable conditions has enormous importance in our society: DNA, sugars, proteins, the molecules of nature, drugs, insecticides and vitamins represent just some of the classes of molecule essential to the way we live our lives. As a result, the discovery of new and improved ways to synthesise new and improved molecules is at the forefront of modern chemistry research. The use of metal catalysis and photochemistry offers substantial improvements to both the synthesis of existing molecules and the discovery of new ones, which can have wide application in medicine, engineering and agriculture.
The overall objective is to harness visible light to control the behaviour of metal catalysts in chemical reactions.
DC meta investigated a large number of reaction systems based around the transition metal ruthenium (Ru). We had previously established a number of novel catalysis systems in the area of C-H activation, which operated at high temperature. For this project, we concentrated on bringing the C-H activation into the room temperature regime through the agency of visible light. We were successful in our objective for one main catalysis system that occupied the majority of the research activity - Ru-ortho arylation of arenes. This transformation proceeds under mild conditions, in good yields and is very easy to handle. A wide scope of aryl halides were compatible under standard conditions, producing C-H arylated products that are typically accessed at high temperatures. A thorough scoping of the reaction, along with preliminary mechanistic studies, formed the basis for a paper communicated to the peer-reviewed literature in 2020 in the journal Chemical Science.
Encouraged by the success of arylation, we turned our attention to other underexplored radical precursors that could grow the system to encompass different building blocks. For this purpose, we synthesised a number of N-Hydroxysuccinimide esters, which are widely being used in photoredox catalysis, and tested them out under the standard conditions. This was largely unsuccessful, despite extensive screening of bases, solvents and the wavelength of light, we tried as well to carry out the reaction at different temperatures, switched to a more powerful and widely applied iridium catalysts with various ligands. Extending this idea to other potential precursors for C-H functionalization gave similar results. Despite our persistent attempts to optimize the conditions, we observed either starting materials or traces of products.
Finally, the project examined another approach to arylation using the Smiles rearrangement, a classic organic chemistry transformation that the Greaney laboratory has worked on extensively. The Fellow recorded a number of promising preliminary results for the sulfonate class of starting materials, which will form the basis of future work in the host laboratory.
The project concluded slightly early, after 21 months out of 24, owing to the Fellow securing a permanent research position elsewhere.
Encouraged by the success of arylation, we turned our attention to other underexplored radical precursors that could grow the system to encompass different building blocks. For this purpose, we synthesised a number of N-Hydroxysuccinimide esters, which are widely being used in photoredox catalysis, and tested them out under the standard conditions. This was largely unsuccessful, despite extensive screening of bases, solvents and the wavelength of light, we tried as well to carry out the reaction at different temperatures, switched to a more powerful and widely applied iridium catalysts with various ligands. Extending this idea to other potential precursors for C-H functionalization gave similar results. Despite our persistent attempts to optimize the conditions, we observed either starting materials or traces of products.
Finally, the project examined another approach to arylation using the Smiles rearrangement, a classic organic chemistry transformation that the Greaney laboratory has worked on extensively. The Fellow recorded a number of promising preliminary results for the sulfonate class of starting materials, which will form the basis of future work in the host laboratory.
The project concluded slightly early, after 21 months out of 24, owing to the Fellow securing a permanent research position elsewhere.
DCMeta has accrued a wide range of results in the area of ruthenium catalysis, C-H activation, and visible-light photochemistry. Part of these have been communicated to the peer-reviewed literature in the international journal Chemical Science, and the body of work underpins our future work in the area in the Greaney laboratory.