Chemical Catalysis
One aspect of our effort focuses on developing the chemistry of the late-transition metal complexes of the N/O-functionalized N-heterocyclic carbene ligands from the perspectives of their utility in homogeneous catalysis namely, the C-C and the C-N bond forming reactions, the polymerization reactions and etc.
Targeting the oxidative addition step of the C-C cross-coupling reaction, we hypothesized that the electron-rich metal center would facilitate the aryl halide activation step, and based on which we study variouspalladium complexes of the types(NHC)2PdX2 (X = halide) and the PEPPSI (Pyridine Enhanced Precatalyst Preparation, Stabilization and Initiation) themed (NHC)PdX2(pyridine) ones in various coupling reactions like the Suzuki-Miyura, Sonogashiraand the Hiyama couplings.
Continuing further along the catalytic construction of the C-C bonds, our interest remains in developing the concept of bifunctional catalysis of the transition metal complexes of the N-heterocyclic carbene ligands, which have largely remained overlooked despite the phenomenal success of these NHC ligands in catalysis.
Using the amido-functionalized N-heterocyclic carbene ligands, our group developed a family ofnickel based bifunctional catalysts for the base-free Michael addition of 1,3-dicarbonyl compounds against activated olefins at room temperature. The chiral bifunctional catalyst variants were successfully used for the asymmetric version of the addition reaction.
Our interest extends beyond the conventional C-C bond forming reactions to the more challenging but environmentally relevant 100 % atom economic hydroamination reactions. Our group designed gold(I) N-heterocyclic carbene complexes for the alkyne hydroamination reaction and the nickel and palladium complexes for the alkene hydroamination reaction. Of prime importance, is our discovery of the role of adventitious water on the kinetics of the reaction as achieved through lowering of the reaction transition state by the active participation of awater molecule in a 1,3-proton shuttle step.
Quite remarkably, our group demonstrated the utility of inert coinage metals in its gold(I) and silver(I)complexes in the Ring Opening Polymerization (ROP) of L-lactides that proceeded viaa coordination-insertion pathway. Significantly enough, our group reported the first example of a gold based initiator for the polymerization reaction.
Our group reported the utility of Au(III) N-heterocyclic carbene complexes as catalysts for the synthesis of -enaminones from 1,3-dicarbonyl compounds and aliphatic amines.
Biomedical applications
On the biomedical application front, our group was among the firsts to highlight the promising potential of palladium N-heterocyclic carbene complexes in anticancer studies. In particular, a palladium N-heterocyclic carbene complex was found to be ~ 2-20 times more active than the frequently used metallodrug, cisplatin, against three commonly occurring human cancer cell lines namely, cervical cancer (HeLa), breast cancer (MCF-7), and colon adenocarcinoma (HCT 116) under analogues in-vitroconditions. The palladium complex inhibited cancer cell proliferation by arresting the cell cycle progression at the G2/M phase.
Our group investigated the application of the silver and gold N-heterocyclic carbene complexes in antimicrobial studies. The cell morphological studies suggested that the metal complexes affected the cytokinesis step of the cell division.
We also designed encapsulated nickel complexesstabilized by strongly chelating N-heterocyclic carbene ligandsshowing subdued cytotoxicity with the intent of their potential application as immunotolerent agents.
Non-N-heterocyclic carbene Chemistry
Apart from the N-heterocyclic carbenes, our other interest lies in olefin polymerization and in oxidation reactions. Of special mention are our groups work on titanium isopropoxide based precatalysts for the sulfoxidation reaction, the biomimetic modeling of galactose oxidase, catechol dioxygenase and catechol oxidase enzymes employing small molecule synthetic analogs of copper and iron respectively. Using homoscorpionatopyrazole derived palladium precatalysts, our group also reported the Suzuki-Miyaura C-C cross-coupling of the more challenging aryl chloride substrates.
One aspect of our effort focuses on developing the chemistry of the late-transition metal complexes of the N/O-functionalized N-heterocyclic carbene ligands from the perspectives of their utility in homogeneous catalysis namely, the C-C and the C-N bond forming reactions, the polymerization reactions and etc.
Targeting the oxidative addition step of the C-C cross-coupling reaction, we hypothesized that the electron-rich metal center would facilitate the aryl halide activation step, and based on which we study variouspalladium complexes of the types(NHC)2PdX2 (X = halide) and the PEPPSI (Pyridine Enhanced Precatalyst Preparation, Stabilization and Initiation) themed (NHC)PdX2(pyridine) ones in various coupling reactions like the Suzuki-Miyura, Sonogashiraand the Hiyama couplings.
Continuing further along the catalytic construction of the C-C bonds, our interest remains in developing the concept of bifunctional catalysis of the transition metal complexes of the N-heterocyclic carbene ligands, which have largely remained overlooked despite the phenomenal success of these NHC ligands in catalysis.
Using the amido-functionalized N-heterocyclic carbene ligands, our group developed a family ofnickel based bifunctional catalysts for the base-free Michael addition of 1,3-dicarbonyl compounds against activated olefins at room temperature. The chiral bifunctional catalyst variants were successfully used for the asymmetric version of the addition reaction.
Our interest extends beyond the conventional C-C bond forming reactions to the more challenging but environmentally relevant 100 % atom economic hydroamination reactions. Our group designed gold(I) N-heterocyclic carbene complexes for the alkyne hydroamination reaction and the nickel and palladium complexes for the alkene hydroamination reaction. Of prime importance, is our discovery of the role of adventitious water on the kinetics of the reaction as achieved through lowering of the reaction transition state by the active participation of awater molecule in a 1,3-proton shuttle step.
Quite remarkably, our group demonstrated the utility of inert coinage metals in its gold(I) and silver(I)complexes in the Ring Opening Polymerization (ROP) of L-lactides that proceeded viaa coordination-insertion pathway. Significantly enough, our group reported the first example of a gold based initiator for the polymerization reaction.
Our group reported the utility of Au(III) N-heterocyclic carbene complexes as catalysts for the synthesis of -enaminones from 1,3-dicarbonyl compounds and aliphatic amines.
Biomedical applications
On the biomedical application front, our group was among the firsts to highlight the promising potential of palladium N-heterocyclic carbene complexes in anticancer studies. In particular, a palladium N-heterocyclic carbene complex was found to be ~ 2-20 times more active than the frequently used metallodrug, cisplatin, against three commonly occurring human cancer cell lines namely, cervical cancer (HeLa), breast cancer (MCF-7), and colon adenocarcinoma (HCT 116) under analogues in-vitroconditions. The palladium complex inhibited cancer cell proliferation by arresting the cell cycle progression at the G2/M phase.
Our group investigated the application of the silver and gold N-heterocyclic carbene complexes in antimicrobial studies. The cell morphological studies suggested that the metal complexes affected the cytokinesis step of the cell division.
We also designed encapsulated nickel complexesstabilized by strongly chelating N-heterocyclic carbene ligandsshowing subdued cytotoxicity with the intent of their potential application as immunotolerent agents.
Non-N-heterocyclic carbene Chemistry
Apart from the N-heterocyclic carbenes, our other interest lies in olefin polymerization and in oxidation reactions. Of special mention are our groups work on titanium isopropoxide based precatalysts for the sulfoxidation reaction, the biomimetic modeling of galactose oxidase, catechol dioxygenase and catechol oxidase enzymes employing small molecule synthetic analogs of copper and iron respectively. Using homoscorpionatopyrazole derived palladium precatalysts, our group also reported the Suzuki-Miyaura C-C cross-coupling of the more challenging aryl chloride substrates.
