Palladium Photocatalysis :
The merger of transition metal catalysis and photocatalysis has provided a platform for the development of highly efficient synthetic methodologies via entirely new mechanistic paradigms. This redefining of chemistry is forged either by a modulated oxidation state or in situ generation of an excited catalytic species through intersystem energy transfer. Converging the appealing properties and complementary reactivities of palladium catalysis with photocatalysis has the potential of creating diverse CH activation manifolds in a sustainable manner.
Despite the applicability of the traditional approach in different fields of C-H activation, the problem associated is reactivity and regioselectivity issues that has rendered it redundant. Often high thermal energy required to promote olefination leads to multiple site functionalization’s. To this aim we as a group trying to develop a photoredox catalytic system constituting a merger of palladium/organo-photocatalyst that forges different functionalization in an explicit regioselective fashion with diverse arenes and heteroarenes. The catalytic system will also amenable towards proximal and distal position aided by respective directing groups (DGs), which entails the versatility of the protocol in engaging the entire spectrum of C(sp2)-H bond functionalization.
Representative Publications:
1. Photoinduced Regioselective Olefination of Arenes at Proximal and Distal Sites
Saha, A.;† Guin, S.;† Ali, W.; Bhattacharya, T.; Sasmal, S.; Goswami, N.; Prakash, G.; Sinha, S. K.; Chandrashekar, H. B.; Panda, S.; Anjana, S. S.; Maiti, D. J. Am. Chem. Soc., 2022, 144, 1929.
2. Substrate-Rhodium Cooperativity in Photoinduced ortho-Alkynylation of Arenes
Saha, A.; Ghosh, A.; Guin, S.; Panda, S.; Mal, D. K.; Majumdar, A.; Akita, M.; Maiti, D. Angew. Chem. Int. Ed., 2022, 61, e202210492
3. Photoinduced meta-Selective C-H Oxygenation of Arenes
Ali, W.;† Saha, A.;† Ge, H.; Maiti, D. JACS Au, 2023, 3, 1790.
Nickel Photocatalysis :
Diverse and selective functionalization of aromatic compounds promise facile construction of biologically active and structurally complex molecules Over the past decade, investigation of nickel reveals it proclivity to both accept and generate reactive radical species by visible light photoredox catalysis could be intercepted to effect cross coupling.
Ni/photoredox catalysis has been demonstrated to be a powerful platform for conducting challenging cross-coupling reactions under mild conditions. Characteristic of these reactions is excitation of a visible-light-absorbing photoredox catalyst. However, catalytic Ni species can also absorb visible light, and several reports have demonstrated the importance of excited Ni species in Ni/photoredox reactions. Our group is focused on developing Ni/photoredox catalysis has since emerged as a versatile platform for the development of a broad array of C–C and Heteroatom bond-forming methodologies.
Representative Publications:
1. Photo-Excited Nickel-Catalyzed Silyl-Radical-Mediated Direct Activation of Carbamoyl Chlorides To Access (Hetero)aryl Carbamides
Maiti, S.;† Roy, S.;† Ghosh, P.; Kasera, A.; Maiti, D. Angew. Chem. Int. Ed., 2022, 61, e202207472.
Photo-induced cross-electrophilic coupling :
Transition metal catalyzed cross-coupling is a versatile tool for the construction of (hetero)biaryl scaffolds. However, the cross-electrophile coupling using abundant (hetero)aryl halides and pseudohalides is still in its infancy. In particular, a robust and general method for the cross-electrophile coupling would allow unparalleled entry into the vast collection of commercially available, structurally-diverse (hetero)aryl halides and pseudohalides as coupling partners. We demonstrate herein a ligand controlled visible light driven monometallic cross-electrophile coupling platform in which the synergistic operation of dual palladium catalytic cycle differentiates the electrophiles based on the bond dissociation enthalpy. This method is mild, robust, selective, and displays unique efficacy towards a wide range of functional groups and challenging heteroaryls, providing access to structurally diverse (hetero)biaryl scaffolds. The power of the transformation has been revealed through the synthesis of (hetero)biaryl core of various pharmaceuticals, and diversification of peptides. More than 55% new (hetero)biaryl core synthesis has been demonstrated, opening up an expanded chemical space for further exploration in functional materials, drug discovery, and bioconjugation-based therapeutics development. Bypassing the traditional transmetalation step, this technology enables a general strategy for the cross-electrophile coupling of (hetero)aryl halides and pseudohalides.
Representative Publications:
1. Light-induced Pd catalyst enables C(sp2)–C(sp2) cross-electrophile coupling bypassing the demand for transmetalation
Maiti, S.; Ghosh, P.; Raja, D. K.; Ghosh, S.; Chatterjee, S.; Sankar, V.; Roy, S.; Lahiri, G. K.; Maiti, D.