Periodic Reporting for period 1 - PhotoCuRiOT (Visible Light-Mediated Copper Photoredox-Catalyzed Ring-Opening Transformations of Activated Small Ring Aza-Heterocycles and Carbacycles)
Periodo di rendicontazione: 2018-04-01 al 2020-03-31
The primary objectives of PhotoCuRiOT were the demonstration of the concept of visible-light-induced homolysis (VLIH) unambiguously and the development of novel synthetic tactics by photooxidation of small molecules to generate open-shell intermediates that can be productively harnessed for the synthesis of a range of high-value functional motifs. Considering the earth abundance, low cost, and low toxicity, Cu(I/II)-based complexes, especially copper(I/II) phenanthroline derivatives, have been planned to use as efficient photocatalysts instead of commonly-used Ru or Ir-based complexes. The initial plan involved the employment of small ring aza-heterocycles and aminocarbacyles which would supposedly get photooxidized by an in situ generated Cu(II) photocatalyst via VLIH, to generate reactive amino radical cationic intermediates that could undergo successive ring-opening and annulation with suitably functionalized nucleophiles to produce biologically significant cyclic and acyclic nitrogenous organic compounds. PhotoCuRiOT has also aimed to bridge the gap between the fields of medicine and energy by enabling facile and highly selective synthesis of a wide array of high-value organic compounds by utilizing first-row transition metal (e.g. Cu) complexes as environmentally benign photoredox catalysts and visible-light as a sustainable source of energy.
The project has achieved most of its objectives and milestones in terms of technical aspects and developments, discovered new directions in earth-abundant metal-complex-based visible-light photocatalysis, and it has fully achieved its parallel objectives regarding the researcher’s training, transfer of knowledge, and fostering his development towards an independent researcher.
Fluorinated and trifluoromethylated organic compounds are of great importance in medicinal chemistry as they productively enhance the pharmacological and physicochemical properties of the molecules. Cognizant of these facts, diverse functionalization of organic chemical feedstocks such as olefins was next undertaken to directly access new chemical spaces which would otherwise be difficult to access. An extensively long screening study with different photocatalysts including Cu(I/II)-based phenanthroline derivative complexes, commonly employed Ir(III)- and Ru(II)-based photocatalysts, Fukuzumi’s catalyst, and first-row transition metal-based [Fe(III), Co(II), Ni(II), Cu(II), and Zn(II)] tetraphenylporphyrin complexes was carried out for efficient oxotrifluoromethylation of vinyl arenes without any significant success. Then, the researcher explored the possibility of a newer class of Fe(II)-based photocatalysts and synthesized a range of photoactive Fe(II)-complexes. Subsequently, a novel process for visible-light-induced Fe(III)-catalyzed photooxidative bifunctionalization of olefins has been developed. The method provides easy access to a wide range of α-trifluoromethylated ketones, ketoazides, and oxoarylsulfonylated derivatives from vinyl arenes in good yields. The developed process can be exploited in the late-stage functionalization of biologically important molecules. The results of the studies are being prepared in a manuscript and will be communicated in the form of a journal article in due course. During the duration of the project, the researcher was also involved in an ongoing work dealing with unusual cycloaddition of amine substituent-containing polycyclic compounds. The results are also in the process of being communicated in a top tier journal for publication.