Research Projects

Nitrile, a polar unsaturated triple bond is sufficiently stable but can be converted to many other functional groups such as acids, amides, ketones which make it an important group in organic synthesis. Lately, with the aid of transition metals, various cascade addition/cyclization has been developed leading to C-C, C=N, and C=O bonds in decorated substrates. Usually, boronic acid is added to the cyano group through a catalytic carbometallation or a radical process leading to ketones, amides, carbocycles and N,O-heterocycles. Recently, we have found that thiol radicals generated under a photocatalytic condition in the presence of a photo-redox catalyst can trigger similar cascade reactions in designer nitrile-containing substrates without the aid of any additives or metal catalysts. For the photocatalytic cascade reaction, usually, two electrophilic sites are necessary. The substrates investigated are classified in the four main categories: (i) Nitrile-carbonyl systems; (ii) di-nitrile and nitrile-amino systems; (iii) nitrile alkyne systems, and (iv) other miscellaneous systems. Various photo catalysts such as Eosin Y, Rose Bengal, 9-mesityl-10-methylacridinium perchlorate [Acr-Mes]+ClO4-, Ir-based catalyst shall be employed. Besides these traditional photocatalysts, the next generation catalysts such as Thermally Activated Delayed Fluorescent (TADF) such as 2,4,5,6-tetra(carbazol-9-yl)benzene-1,3-dicarbonitrile (4CzIPN), 3DPA2FBN, and 3DPAFIPN shall be employed. The illustrative schemes in this project are with thiol-radical, but other N-centered radicals, SO2F and CF3 radicals etc., will also be explored for triggering the cascade reactions. Each of the proposed schemes would generate an interesting heterocyclic skeleton. For multiple electrophilic sites containing substrates, the product will be characterized and an appropriate mechanism shall be proposed. Based on the product obtained the reactivity trend shall be rationalized. The synthesized products shall be subjected to various biological evaluations.

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