Early attempts to oxidize N-activated and donor-acceptor aziridines with Cu(I/II)-photocatalysts and subsequent reaction with various nucleophiles met with little success. Moreover, similar work on photocatalytic ring-opening reactions of aziridines with nucleophiles as originally proposed in the project was published concurrently. Therefore, the subsequent focus of the project objectives was directed towards developing novel photooxidative transformations of other small organic molecules by employing various first-row transition metal-based photocatalysts. In this vein, the use of Cu in visible-light photoredox catalysis and its recent upsurge have been chronicled and highlighted in a top tier journal (Science 2019, 364, eaav9713) where it was shown that Cu(I) and Cu(II) complexes can act as standalone photocatalysts, in situ generated Cu(I)-substrate complexes can be photoexcited, Cu can be used in cooperative photoredox-Cu dual catalysis, and other miscellaneous ways.
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.
