1/7/2023 0 Comments Photoflow screen printsFirst, the fundamentals of photochemistry are detailed, including the importance of photons for the observed reaction kinetics, the key photochemical laws, and some guidelines for the appropriate light source selection. Herein, we aim to give a detailed perspective on the new technological advances observed within the field of photochemistry and photocatalysis for synthetic organic chemistry. (46) Photochemistry can play a key role in this transition since light can be regarded as a renewable, traceless reagent, (47−49) and most photochemical processes adhere to the principles of green chemistry. ![]() In times of increasing environmental awareness, another strong indicator for this statement is that the chemical industry is required to develop more sustainable and energy-efficient processes with reduced waste generation and minimal environmental impact. (45) Therefore, it can be argued that it is actually the combination of these three different technologies (i.e., photocatalysis, light sources and reactor technology), which have developed independently and with their own set of rules, that could ensure that photochemistry is here to stay. (4) On the contrary, several important contributions were made already decades ago. However, it is important to note that the application of photocatalysis in organic synthesis is not a recent invention. (43,44) Several companies have focused on developing and commercializing standardized equipment to carry out photocatalytic transformations on different scales. (42) And third, various advanced photochemical reactor technologies have been developed in recent years, which show great promise to carry out photochemical processes ranging from laboratory to production scale. (41) Second, the tremendous evolution of light-emitting diode (LED) technology has resulted in the development of monochromatic, energy efficient, durable, and high intensity light sources, reducing the effective costs of photons for photochemical applications. (40) It is remarkable to see how fast companies have established small groups of experts to investigate the potential impact of photocatalysis in their synthetic programs. ![]() The first reason for this statement is the rapid uptake and maturation of photocatalysis in both academia and industry, allowing researchers to completely rethink the assembly of organic molecules. Nevertheless, this time the moment could be right for a definitive breakthrough of synthetic photochemistry in the industry. Photochemistry was only considered when there was no alternative available, such as in the production of vitamin D and rose oxide as prime examples. ![]() The general perception was to avoid photochemistry altogether as it imposed too many insurmountable issues to bring the molecule to the market. (38) This undermined the confidence of researchers─especially in the fine-chemical industry─to integrate photochemical steps in their synthetic routes toward pharmaceuticals, agrochemicals, and materials. (34−36) Also from a scale-up perspective, photochemistry is still regarded as a daunting challenge because of the high cost of photons (37) and the light absorption, which causes a gradual loss of light intensity through the reaction medium. In one of the earlier reviews on photochemistry, (33) Noyes and Kassel stated already in the first paragraph that “ Unfortunately, while Photochemistry may be said to be much older than its fellows, it is at present in a far more unsatisfactory state.” Indeed, photochemical transformations are often perceived as very complex with regard to reaction kinetics. ![]() However, although the use of photons in organic synthesis is as old as the field itself, (32) it was consistently met with skepticism.
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