@article {48102, title = {Room temperature chemoselective hydrogenation of C=C, C=O and C=N bonds by using a well-defined mixed donor Mn(I) pincer catalyst}, journal = {Chemical Science}, volume = {13}, year = {2022}, month = {NOV }, pages = {13764-13773}, type = {Article}, abstract = {

Chemoselective hydrogenation of C=C, C=O and C=N bonds in alpha,beta-unsaturated ketones, aldehydes and imines is accomplished at room temperature (27 degrees C) using a well-defined Mn(I) catalyst and 5.0 bar H-2. Amongst the three mixed-donor Mn(I) complexes developed, kappa(3)-((PNNPyz)-P-R2-N-3)Mn(CO)(2)Br (R = Ph, Pr-i, Bu-t); the Bu-t -substituted complex ((PNNPyz)-P-tBu2-N-3)Mn(CO)(2)Br shows exceptional chemoselective catalytic reduction of unsaturated bonds. This hydrogenation protocol tolerates a range of highly susceptible functionalities, such as halides (-F, -Cl, -Br, and -I), alkoxy and hydroxy, including hydrogen-sensitive moieties like acetyl, nitrile, nitro, epoxide, and unconjugated alkenyl and alkynyl groups. Additionally, the disclosed method applies to indole, pyrrole, furan, thiophene, and pyridine-containing unsaturated ketones leading to the corresponding saturated ketones. The C=C bond is chemoselectively hydrogenated in alpha,beta-unsaturated ketones, while the aldehyde{\textquoteright}s C=O bond and imine{\textquoteright}s C=N bond are preferentially reduced over the C=C bond. A detailed mechanistic study highlighted the non-innocent behavior of the ligand in the ((PNNPyz)-P-tBu2-N-3) Mn(I) complex and indicated a metal-ligand cooperative catalytic pathway. The molecular hydrogen (H-2) acts as a hydride source, whereas MeOH provides a proton for hydrogenation. DFT energy calculations supported the facile progress of most catalytic steps, involving a crucial turnover-limiting H-2 activation.

}, issn = {2041-6520}, doi = {10.1039/d2sc05274a}, author = {Shabade, Anand B. and Sharma, Dipesh M. and Bajpai, Priyam and Gonnade, Rajesh G. and Vanka, Kumar and Punji, Benudhar} } @article {48723, title = {Pd nanoparticles supported on N-incorporated hybrid organosilica as an active and selective low-temperature phenol hydrogenation catalyst}, journal = {ACS Applied Nano Materials}, volume = {6}, year = {2023}, month = {JUN}, pages = {11500-11512}, type = {Article}, abstract = {

A heterogeneous Pd-NPMO hybrid-silicacatalyst is synthesized andits application for aqueous phase selective hydrogenation of phenolto cyclohexanone at near ambient temperature (40 degrees C) and underatmospheric hydrogen pressure is demonstrated. The homogeneously distributedPd nanoparticles on N-bridged hybrid mesoporous organosilica showedremarkable activity and selectivity for cyclohexanone compared tothe unmodified Pd-SBA-15 catalyst. Control experiments strongly claimthe role of nitrogen domains in the organic framework of hybrid silicasupport in stabilizing small Pd nanoparticles and possibly modifyingthe Pd sites responsible for catalysis to activate the substrate moleculesin water. The hybrid silica catalyst was stable and reused severaltimes without any significant drop-in activity, proving the heterogeneityof the bifunctional Pd catalyst. Based on the density functional theorystudy and experimental interventions, a possible reaction mechanismfor the low-temperature phenol hydrogenation explaining the role oforganic domains in the hybrid-silica framework is proposed.

}, keywords = {cyclohexanone, Hybrid silica, palladium nanoparticles, Periodic mesoporous organosilica, phenol hydrogenation}, doi = {10.1021/acsanm.3c01540}, author = {Betsy, K. J. and Bajpai, Priyam and Lazar, Anish and Vanka, Kumar and Vinod, C. P.} } @article {49869, title = {The critical helping hand of water: theory shows the way to obtain elusive, granular information about kinetic asymmetry driven systems}, journal = {Chemical Science}, volume = {16}, year = {2025}, month = {AUG }, pages = {14940-14955}, type = {Article}, abstract = {

Kinetic asymmetry is crucial in chemical systems where the selective synthesis of one product over another, or the acceleration of specific reaction(s) is necessary. However, obtaining precise information with current experimental methods about the behavior of such systems as a function of time, substrate concentration and other relevant factors, is not possible. Computational chemistry provides a powerful means to address this problem. The current study unveils a two-pronged computational approach: (i) full quantum chemical studies with density functional theory (DFT), followed by (ii) stochastic simulations with a validated Gillespie algorithm (GA) (using representative model systems where necessary), to study the behavior of a kinetic asymmetry driven unidirectional molecular motor (1-phenylpyrrole2,2 {\textquoteleft}-dicarboxylic acid) (Nature, 2022, 604 (7904), 80-85). Our approach allows us to understand what is really taking place in the system, underlining the crucial role played by water molecules in facilitating the rotation of the motor. It is seen that water lubricates the motion by increasing the rotation rate constant of the final step by, remarkably, more than ten orders of magnitude! These insights further serve to explain the efficient rotation of the very recently reported gel-embedded molecular motor (Nature, 2025, 637 (8046), 594-600), providing an upper limit for the allowed rotation barrier in such systems, and thus also casts light into the functioning of bio-molecular motors. The current work therefore provides a template for carefully and properly studying a wide variety of important, kinetic asymmetry driven systems in the future.

}, issn = {2041-6520}, doi = {10.1039/d5sc03256c}, author = {Bajpai, Priyam and Thulasiram, Shrivatsa and Vanka, Kumar} } @article {49421, title = {Depolymerization of waste polycarbonates to value-added products}, journal = {ChemSusChem}, volume = {18}, year = {2025}, month = {JAN}, type = {Article}, abstract = {

Additive free aminolysis method developed for the depolymerization/upcycling of polycarbonates. We report here chemical recycling of polycarbonate under ambient conditions to get its monomer bisphenol A, monoaminocarbamate and biscarbamates in 1 : 2 : 1 ratio respectively. By employing the secondary amine as the aminating reagent, facilitates the depolymerization to work under additive/catalyst free conditions. The developed method deals with depolymerization of waste polycarbonates and works even with late-stage amine derivatives such as amoxapine and desloratadine which are drugs molecules known to treat neurotic disorders and allergies respectively. The reaction can be scaled up and works with similar efficacy which depicts the efficiency of the depolymerization of wasteend-of-life polycarbonate plastic waste. The biscarbamate and bisphenol-A was further subjected for the post functionalization to obtain amides and phenol in good yields. Developed additive/catalyst free aminolysis of waste polycarbonates to carbamates and monomer BPA at ambient conditions. Variety of secondary amines were screened including the late stage amine derivatives like amoxapine and desloratadine which delivered the expected products successfully. Later the developed methodology was even applied for the different end-of-life polycarbonates with the secondary amine and achieved the depolymerization without any obstacle. Further carried out the scale up reaction and derivatization of carbamates and BPA to amide and phenol synthesis. image

}, keywords = {Aminolysis, carbamates, depolymerization, End-of-life, Polycarbonate}, issn = {1864-5631}, doi = {10.1002/cssc.202400756}, author = {Padhi, Ganeshdev and Pansare, Vaibhav Ramachandra and Bajpai, Priyam and Krishna, Gamidi Rama and Vanka, Kumar and Barsu, Nagaraju} } @article {49834, title = {Palladium(II)-catalyzed desymmetrization of 2-alkynylbenzoate-tethered cyclohexadienones for the synthesis of polycyclic compounds}, journal = {Organic Letters}, volume = {27}, year = {2025}, month = {MAY}, pages = {5429-5434}, type = {Article}, abstract = {

Pd-catalyzed cascade cyclization of 2-alkynylbenzoate-tethered cyclohexadienone was developed for the single step synthesis of isocoumarin-fused dihydrochromenones. This highly atom economical method proceeds via 6-endo-dig cyclization of tert-butyl benzoate with a tethered alkyne. By modulating the reaction solvent and metal catalyst, the methodology was diverted for the purposeful synthesis of either of the E/Z tetra-substituted alkenes.

}, issn = {1523-7060}, doi = {10.1021/acs.orglett.5c01396}, author = {Rai, Archana and Bajpai, Priyam and Gamidi, Rama Krishna and Vanka, Kumar and Das, Utpal} } @article {49775, title = {Unified photoredox-catalyzed aerobic oxidative dynamic kinetic asymmetric transformation for C-N atropoisomers mediated by chiral organophosphites}, journal = {Organic Letters}, volume = {27}, year = {2025}, month = {AUG }, pages = {8171-8177}, type = {Article}, abstract = {

The synthesis of anilides with a chiral C(=O)-N axis has relied on direct installation of the chiral C(sp2)-N(sp2) bond or enantioselective modification of the peripheral groups. However, these methods are constrained by the size and type of functional groups compatible with each strategy. Herein, we report a dynamic kinetic asymmetric transformation (DYKAT) for the aerobic oxidation of iminium ions to access C(=O)-N axial chirality that addresses those limitations. Furthermore, it eliminates the need for any auxiliary functional groups, which enables us to develop a unified method for the synthesis of atroposelective isoquinolone, lactam, and amide.

}, issn = {1523-7060}, doi = {10.1021/acs.orglett.5c02273}, author = {Saikia, Pinku and Aarthika, M. and Bhattacharjya, Ayantika and Maity, Susmita and Bajpai, Priyam and Bera, Asish and Saha, Arindam and Gonnade, Rajesh G. and Vanka, Kumar and Maity, Pradip} } @article {50106, title = {Intramolecular alder-ene reaction of 2-methyl-4-(alkynyloxy)cyclohexa-2,5-dienones: catalyst-free access to hydrobenzofuran derivatives}, journal = {Organic Letters}, volume = {28}, year = {2026}, month = {APR }, pages = {5195-5199}, type = {Article}, abstract = {

An atom-economical intramolecular Alder-ene reaction has been developed to construct hydrobenzofurans via the direct coupling of an allylic hydrogen atom to an alkyne. This transformation delivers hydrobenzofuran and hydroindole scaffolds in a single step, incorporating all atoms of the starting materials and exemplifying high atom economy. The synthesized products serve as versatile intermediates and exhibit notable reactivity toward further derivatization, as showcased through a range of transformations enabling rapid access to structurally diverse and complex molecules.

}, issn = {1523-7060}, doi = {10.1021/acs.orglett.6c01057}, author = {Rai, Archana and Bajpai, Priyam and Kundu, Ananya I. and Vanka, Kumar and Das, Utpal} }