Research Projects

Coumarin derivatives especially 3,4-dihydro coumarins belong to the class of compounds frequently encountered in natural products and drug molecules. They possess numerous activities like anti-HIV, anti-oxidant, anti-tumor, etc. To show different bioactivities proper substitution at proper positions of coumarin is crucial. Therefore, functionalization of coumarin derivatives is always interesting and lots of work have been done on it using conventional techniques. To explore the visible light induced functionalization as an effective green tool here we aim to develop a sustainable route to the synthesis of functionalized coumarin derivatives utilising visible light photochemistry. The functionalization is mostly focused on C-3 and C-4 position of coumarin-3-carboxylic acid derivatives. First, different derivatives of coumarin-3-carboxylic acid will be prepared followed by visible light induced regioselective functionalization on these derivatives will be attempted to achieve the target products, viz., C-4 arylation as well as alkylation, C-3 alkylation, and C-4 hetero functionalization, via a decarboxylative pathway. In contrast to the literature reported C-3 alkylation here in this project, we will explore other alkylating partners such as xanthate esters, acyl halides, and 1,4-dihydropyridine derivatives. similarly, for C-4 arylation we will explore the possibility of using aryl radical precursors such as aryl diazonium salts, phenyl hydrazines, and aryl halides. Most interestingly we can add the in situ generated alkyl or aryl radicals to the C-3 position by blocking C-4 position of coumarin-3-carboxylic acid. For hetero functionalization, we will choose the C-4 position rather than C-3 position, where most of the works are reported, i.e., diaryldiselenide, aryl sulphide. KsCN or KseCN, and diaryl phosphine oxide etc.