02129nas a2200157 4500008004100000245004500041210004400086260000800130300001100138490000600149520166800155100002401823700002401847700002001871856008001891 2023 eng d00aMetal-catalyzed plastic depolymerization0 aMetalcatalyzed plastic depolymerization cMAY a1013410 v43 a

Polymers have become an indispensable part of our daily lives, and today we produce around 370 MT of plastic per year. Only about 20% of it is being recycled, and the rest, 80%, is unleashed into the environment without appropriate treatment. This calls forth the evaluation of strategies available for mitigating the menace of ``after-use''plastic waste. Various approaches have evolved over a decade and are at different levels of development. Plastic depolymerization and upcycling are considered some of the most prominent and long-term solutions. The metal-catalyzed depolymerization of plastic waste to chemical feedstocks has emerged as one of the promising ways to address global plastic pollution. Therefore, this review aims to examine the available metal-catalyzed depolymerization methods, notify recent progress, pinpoint current gaps, and gauge the potential of this strategy. Both homogeneous and heterogeneous catalysts have been reported to depolymerize various polymers over the last decade. Considerable advances have been reported in the metal-mediated depolymerization of polyolefins, polyesters, polycarbonates, polyurethanes, polyamides, and polyethers. The depolymerization of the above polymers produces the monomers or intermediates, which can be used again for polymerization and thus brings the waste polymers back into circularity. The overview debates the usage of high temperaagents, etc., in metal-catalyzed depolymerization. Thus, this review summarizes the current understanding of the fundamental science of metal-catalyzed plastic depolymerization, the remaining scientific challenges, and the potential opportunities.

1 aKhopade, Kishor, V.1 aChikkali, Samir, H.1 aBarsu, Nagaraju uhttps://library.ncl.res.in/content/metal-catalyzed-plastic-depolymerization00825nas a2200229 4500008004100000022001400041245012100055210006900176260001000245300001600255490000700271653001600278653002800294653002100322653001900343653002500362100002600387700002100413700001800434700002000452856012300472 2024 eng d a2168-048500aCopper/Iron cocatalyzed depolymerization of postconsumer polycarbonate: a one-pot strategy to synthesize aryl ethers0 aCopperIron cocatalyzed depolymerization of postconsumer polycarb cDEC 7 a18362-183720 v1210aaryl ethers10acopper/iron cocatalysis10adepolymerization10apolycarbonates10aValue-added products1 aMoyilla, Nageswararao1 aPadhi, Ganeshdev1 aKalsi, Deepti1 aBarsu, Nagaraju uhttps://library.ncl.res.in/content/copperiron-cocatalyzed-depolymerization-postconsumer-polycarbonate-one-pot-strategy02091nas a2200193 4500008004100000022001400041245010700055210006900162260000800231300001600239490000700255520138000262100002401642700002401666700003101690700002001721700002401741856013201765 2024 eng d a1463-926200aDepolymerization of waste polyethylene to linear alkenes via sequential dehydrogenation and metathesis0 aDepolymerization of waste polyethylene to linear alkenes via seq cOCT a10558-105660 v263 a

Polyethylene (PE) is the most abundantly sourced plastic and significant efforts are needed for its end-of-life management. The deconstruction of PE is an uphill task and requires the breaking of highly stable C-C bonds. Here we demonstrate that PE can be deconstructed to value-added dodecene, along with other long-chain alkenes. The PCP-iridium complex catalyzes the dehydrogenation of commercial and post-consumer polyethylene waste to produce dehydrogenated polyethylene (DHP) with 0.5-1.0% unsaturation. The DHP was subjected to an ethylene cross-metathesis reaction in the presence of suitable catalysts. Through meticulous optimization of reaction parameters, 63% selectivity toward dodecene, with 26% overall yield, was achieved. The practical significance of our method has been demonstrated by subjecting post-consumer plastic waste to dehydrogenation followed by ethylene metathesis to produce dodecene as a major product, together with long-chain alkenes. The PE deconstruction has been confirmed by recording molar mass before and after depolymerization using high-temperature gel permeation chromatography. The existence of dodecene has been unambiguously ascertained using GC, GC-MS, NMR, and IR spectroscopy. Thus, these results demonstrate the conversion of waste PE to value-added dodecene and long-chain alkenes under mild reaction conditions.

1 aKhopade, Kishor, V.1 aRajput, Nikhita, S.1 aRangappa, Raghavendrakumar1 aBarsu, Nagaraju1 aChikkali, Samir, H. uhttps://library.ncl.res.in/content/depolymerization-waste-polyethylene-linear-alkenes-sequential-dehydrogenation-and-metathesis00980nas a2200157 4500008004100000022001400041245007100055210006900126260000900195300001200204490000700216520044300223100003300666700002000699856010300719 2025 eng d a1477-052000aBase-mediated denitrative C3-alkylation of quinoxaline derivatives0 aBasemediated denitrative C3alkylation of quinoxaline derivatives cJAN  a303-3070 v233 a

We have developed a novel base-mediated method for the selective C3-alkylation of quinoxalin-2(1H)-one and N-protected quinoxalin-2(1H)-one using inexpensive, unactivated nitroalkanes. This approach tolerates a wide range of functional groups and supports the synthesis of various bioactive compounds. Gram-scale reactions demonstrate the scalability of the method. The proposed mechanism was validated by control experiments.

1 aPansare, Vaibhav, Ramachandr1 aBarsu, Nagaraju uhttps://library.ncl.res.in/content/base-mediated-denitrative-c3-alkylation-quinoxaline-derivatives02337nas a2200253 4500008004100000022001400041245006900055210006800124260000800192490000700200520155700207653001501764653001501779653002101794653001601815653001801831100002101849700003301870700001901903700002601922700001701948700002001965856009801985 2025 eng d a1864-563100aDepolymerization of waste polycarbonates to value-added products0 aDepolymerization of waste polycarbonates to valueadded products cJAN0 v183 a

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

10aAminolysis10acarbamates10adepolymerization10aEnd-of-life10aPolycarbonate1 aPadhi, Ganeshdev1 aPansare, Vaibhav, Ramachandr1 aBajpai, Priyam1 aKrishna, Gamidi, Rama1 aVanka, Kumar1 aBarsu, Nagaraju uhttps://library.ncl.res.in/content/depolymerization-waste-polycarbonates-value-added-products02171nas a2200241 4500008004100000245011900041210006900160260000800229490000700237520131600244653001901560653002601579653001401605653001401619653001801633100002101651700002401672700002601696700003101722700002401753700002001777856013201797 2025 eng d00aRuthenium-catalyzed deconstruction of polyolefins: a strategy to up-cycle waste polyethylene to value-added alkene0 aRutheniumcatalyzed deconstruction of polyolefins a strategy to u cAPR0 v643 a

Synthesis of value-added products from post-consumer waste polyolefins is fascinating as well as challenging. Here we report ruthenium-catalyzed up-cycling of the polyethylene to long-chain alkene derivatives. The developed methodology mainly involves two steps i.e., dehydrogenation of polyethylene through hydrogen atom transfer and its metathesis using the HG-II catalyst. The dehydrogenation of polyethylene using ruthenium catalysis derived up to 3.38 %, of double bonds; with 90 % of the recovered polyolefin material. The obtained unsaturated polyethylene was subjected to cross-metathesis with ethylene using HG-II catalytic system. This resulted in the synthesis of predominantly dodecene (C12) derivatives, with 58 % selectivity, along with other derivatives of varying chain lengths. The overall reaction produced terminal and internal olefins in the ratio 1:0.8 respectively. The dehydrogenation of polyethylene and its deconstruction was confirmed by NMR spectroscopy, Gel Permeation Chromatography (GPC) and Differential Scanning Calorimetry (DSC). The origin of C12 selectivity has been demonstrated by control experiments. The scope of the methodology was extended to post-consumer waste polyethylene which gave high conversion to value-added dodecene derivatives as a major product.

10aDeconstruction10aHomogeneous catalysis10aruthenium10aUpcycling10aWaste plastic1 aPadhi, Ganeshdev1 aKhopade, Kishor, V.1 aMoyilla, Nageswararao1 aRangappa, Raghavendrakumar1 aChikkali, Samir, H.1 aBarsu, Nagaraju uhttps://library.ncl.res.in/content/ruthenium-catalyzed-deconstruction-polyolefins-strategy-cycle-waste-polyethylene-value-added01149nas a2200169 4500008004100000022001400041245011300055210006900168260000800237300001600245490000700261520050700268100002600775700002100801700002000822856013700842 2025 eng d a1463-926200aSustainable base-mediated chemical upcycling of poly (propylene carbonate) to β-hydroxy sulfides and oxides0 aSustainable basemediated chemical upcycling of poly propylene ca cSEP a10543-105490 v273 a

We present a cesium carbonate-mediated method to upcycle poly(propylene carbonate) (PPC) waste into beta-hydroxy sulfides, selenides, and phenoxides via selective thermal depolymerization. The process tolerates diverse nucleophiles, including those from multilayer plastics. Mechanistic studies support a cesium aryl thiolate-driven nucleophilic degradation. The beta-hydroxy products are easily functionalized, and the base is recyclable, offering a sustainable route for PPC valorization.

1 aMoyilla, Nageswararao1 aPadhi, Ganeshdev1 aBarsu, Nagaraju uhttps://library.ncl.res.in/content/sustainable-base-mediated-chemical-upcycling-poly-propylene-carbonate-%CE%B2-hydroxy-sulfides-and01470nas a2200229 4500008004100000022001400041245009300055210006900148260000900217300000700226490000800233520072600241653001100967653001900978653002800997653002401025653001501049653001901064100001601083700002001099856012101119 2026 eng d a0974-362600aPhosphine radical cation catalysis for Markovnikov hydroamination of unactivated alkenes0 aPhosphine radical cation catalysis for Markovnikov hydroaminatio cAPR  a510 v1383 a

Markovnikov-selective hydroamination of unactivated terminal alkenes has long remained a challenging transformation in C-N bond formation. Fan and co-workers1 addressed this using a metal-free phosphine photoredox system that operates via an unprecedented phosphine radical cation (P(IV)) mechanism, enabling alkene activation toward azole addition. This work highlights a powerful new strategy for C(sp3)-N bond construction beyond traditional transition-metal catalysis.Graphical abstractMetal-free phosphine photoredox catalysis enables Markovnikov-selective hydroamination of unactivated terminalalkenes via a novel phosphine radical cation mechanism, off ering a new strategy for C(sp3)-N bond formation.

10aazoles10ahydroamination10aMarkovnikov selectivity10aPhosphine catalysis10aphotoredox10aradical cation1 aDas, Nirmal1 aBarsu, Nagaraju uhttps://library.ncl.res.in/content/phosphine-radical-cation-catalysis-markovnikov-hydroamination-unactivated-alkenes00988nas a2200157 4500008004100000245009500041210006900136260000900205300001400214490000700228520039600235100003300631700002000664700002000684856012600704 2026 eng d00aSite-selective iron-catalyzed C-H alkylation of pyrazinones, azauracils and quinoxalinones0 aSiteselective ironcatalyzed CH alkylation of pyrazinones azaurac cMAY  a2725-27290 v133 a

Described herein is an unprecedented iron-catalyzed C(sp2)-H alkylation of pyrazinone, azauracil, and quinoxalinone analogues using ethers and benzyl derivatives, offering broad scope and high functional group tolerance. The method is scalable and enables downstream functionalization. The mechanistic investigations, such as radical trapping, support a radical-mediated pathway.

1 aPansare, Vaibhav, Ramchandra1 aSreelakshmi, N.1 aBarsu, Nagaraju uhttps://library.ncl.res.in/content/site-selective-iron-catalyzed-c-h-alkylation-pyrazinones-azauracils-and-quinoxalinones