Dual Catalysis: Merging Cobaltoximes with Photocatalysts in DehydrogenativeOrganic Synthesis

Introduction: The broader scientific community of chemists is focused on developing efficient methods for synthesizing new molecules that can benefit society by efficient utilization of accessible energy sources to facilitate chemical reactions. Among the various renewable energy sources, solar energy stands out as one of the most plentiful forms of energy found in nature. In the endeavour to convert solar energy into chemical energy, numerous researchers are focused on developing materials capable of capturing solar light. The captured solar energy can subsequently participate in a chemical reaction by facilitating energy or electron transfer to another substrate, resulting in the production of the intended product. Such a process of converting substrates into products using light is known as photocatalysis, which is regarded as a sustainable approach to conducting organic reactions, especially when visible light is utilized. This mini-review primarily examines the dual photocatalysis involving cobaltoximes and photocatalysts in the context of dehydrogenative organic reactions with the formation of molecular hydrogen gas. Methods: This mini-review was designed following the methodology criteria, like the database search and scope, the inclusion and exclusion criteria, study selection process, and data extraction and analysis. This mini-review discussed the photocatalytic synthetic process which utilizes visible light in the presence of catalytic amounts of cobaltoximes [Co(dmgH)2XY], where X = substituted pyridine & Y = halogen and relevant photocatalysts (Ru, Ir polypyridyl complexes, organic dyes) at room temperature with reaction time duration of 6-48 h. Results: This review underscores several applications where dehydrogenation and coupling reactions are pivotal, whether in the synthesis of novel molecules or in practical applications. The transformation of the substrate into the product was observed to be highly efficient through the photocatalytic pathway, with the application of 1 to 10 mol% of cobaltoximes-photocatalysts resulting in product yields ranging from 70% to 99%. Discussion: This paper elucidates that photocatalytic dehydrogenation reactions represent a method for converting substrates into significant molecules or products with broader applications. However, to date, these reactions are predominantly advantageous only when precious metal photocatalysts are utilized. Conclusion: The present work emphasizes the cooperativity of the photocatalyst and cobaltoximes to unlock the greener routes of the challenging reactions, which generally need harsh reaction-conditions. In the context of the current high demand for energy, it is noteworthy that the products generated from these reactions, which are used in the synthesis of drugs, dyes, and radical intermediates, could also function as energy carriers. Thus, the present work will comprehensively provide diverse information which may help to overcome more challenging situations in the field of applied chemistry.