Photoelectrochemistry and Photochemistry for Sustainable Organic Synthesis

Abstract

To address the sustainability issues of the existing industrial processes for producing fine chemicals and pharmaceuticals, we should develop alternative methods that raise energy efficiency, atom economy and eliminate toxic chemicals.1 One way to do that is to take inspiration from biological systems - Nature itself offers paradigms for sustainability. For decades, the natural systems, and in particular photosynthesis, have provided the principal model for solar-energy science and engineering. Therefore, electron and charge transfer are not only at the core of life-sustaining biological processes (photosynthesis), but also at the core of modern sustainable technology (solar cells, energy storage, energy conversion).2 Regarding sustainable organic synthesis chemists also realized the potential of electron and charge transfer. Electrochemistry3 together with photochemistry4 are one of the greenest ways for driving chemical transformations, since their application improves atom economy, efficiency and prevents generation of toxic wastes.Both of them have given rise to new and efficient access to some of the most reactive intermediates,that are challenging or impossible to generate by traditional chemical methods. Our main efforts concern development of new methods for an ecological and sustainable organic synthesis. On one hand, our work describe the application of NHC-Cu three-coordinate complexes as photocatalysts in energy and electron transfer reactions. Taking into account photophysical properties of NHC-Cu(I) complexes along with the fact that they are straightforward in synthesis, non-toxic, inexpensive and abundant, we envisioned that their application as photocatalysts could provide a general alternative for toxic, expensive and rare Ir- and Ru-based complexes.5 On the other hand, the constructive merge of electrochemistry and photochemistry offers the potential to overcome the drawbacks of one method through the complementary advantages of the other. One of the effective ways for their merge is interfacial photoelectrochemistry (iPEC), where the reaction occurs at photoelectrode surface.6 Our work in this area describes mild and efficient electrochemical methods for [2+1], [2+2] and [2+4] cycloaddition reactions of alkene radical cations.7 Anodic oxidation of olefins at the photoanode surface produces electrophilic alkene radical cations, which further react with nucleophiles in a formal [2+1], [2+2] and [2+4] cycloaddition towards synthesis of 3-,4-,6-membered rings. The advantages of the application of photoelectrodes in organic synthesis include high selectivity, the use on reusable materials, non-precious metal catalysts and lost but not least significant energy savings.[1] R. Gorini at all Energy Strateg. Rev. 2019, 24, 38 [2] Y. Wang, H. Suzuki, J. Xie, O. Tomita, D. J. Martin, M. Higashi, D. Kong, R. Abe, J. Tang Chem. Rev. 2018, 118, 5201 [3] a) S. Waldvogel at all Chem. Sci. 2020, 11, 12386; b) K. D. Moeller Tetrahedron 2000, 56, 9527; c) P. S. Baran at all Chem. Rev. 2017, 117, 13230; [4] a) D.W.C. MacMillan at all J. Org. Chem. 2016, 81, 6898; b) P. Melchiorre at all Angew. Chem. Int. Ed. 2019, 58, 3730; c) T. P. Yoon at all Chem. Rev. 2016, 116, 10035; d) M. Rueping at all Chem. Sci. 2020, 11, 4051; e) F. Glorius at all Chem. Soc. Rev. 2018, 47, 7190. [5] K. Rybicka-Jasińska at all unpublished results; [6] K. Rybicka-Jasińska, V. I. Vullev Charge Transfer & Organic Photoelectrochemistry ACS in focus 2023 DOI: 10.1021/acsinfocus.7e7025 [6] K. Rybicka-Jasińska et all unpublished results