Therapeutic Strategies in HCC: Radiation Modalities

Patients with hepatocellular carcinoma (HCC) comply with an advanced disease and are not eligible for radical therapy. In this distressed scenario new treatment options hold great promise; among them transarterial chemoembolization (TACE) and transarterial metabolic radiotherapy (TAMR) have shown efficacy in terms of both tumor shrinking and survival. External radiation therapy (RTx) by using novel three-dimensional conformal radiotherapy has also been used for HCC patients with encouraging results while its role had been limited in the past for the low tolerance of surrounding healthy liver. The rationale of TAMR derives from the idea of delivering exceptional radiation dose locally to the tumor, with cell killing intent, while preserving normal liver from undue exposition and minimizing systemic irradiation. Since the therapeutic efficacy of TACE is being continuously disputed, the TAMR with 131I Lipiodol or 90Y microspheres has gained consideration providing adequate therapeutic responses regardless of few toxicities. The implementation of novel radioisotopes and technological innovations in the field of RTx constitutes an intriguing field of research with important translational aspects. Moreover, the combination of different therapeutic approaches including chemotherapy offers captivating perspectives. We present the role of the radiation-based therapies in hepatocellular carcinoma patients who are not entitled for radical treatment

Terpolymerization of co2 with epoxides and cyclic organic anhydrides or cyclic esters

The synthesis of polymeric materials starting from CO2 as a feedstock is an active task of research. In particular, the copolymerization of CO2 with epoxides via ring-opening copolymerization (ROCOP) offers a simple, efficient route to synthesize aliphatic polycarbonates (APC). In many cases, APC display poor physical and chemical properties, limiting their range of application. The terpolymerization of CO2 with epoxides and organic anhydrides or cyclic esters offers the possibility, combining the ROCOP with ring-opening polymerization (ROP), to access a wide range of materials containing polycarbonate and polyester segments along the polymer chain, showing enhanced properties with respect to the simple APC. This review will cover the last advancements in the field, evidencing the crucial role of the catalytic system in determining the microstructural features of the final polymer

Stereoregular Polymerization of Acyclic Terpenes

The growing environmental pollution and the expected depleting of fossil resources have sparked interest in recent years for polymers obtained from monomers originating from renewable sources. Furthermore, nature can provide a variety of building blocks with special structural features (e. g. side groups or stereo-elements) that cannot be obtained so easily via fossil-based pathways. In this context, terpenes are widespread natural compounds coming from non-food crops, present in a large variety of structures, and ready to use as monomers with or without further modifications. The present review aims to provide an overview of how chemists can stereospecifically polymerize terpenes, particularly the acyclic ones like myrcene, ocimene, and farnesene, using different metal catalyst systems in coordination-insertion polymerization. Attention is also paid to their copolymers, which have recently been disclosed, and to the possible applications of these bio-based materials in various industrial sectors such as in the field of elastomers. © 2021 The Authors. ChemPlusChem published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution Non-Commercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes

Copolymerization of Ethylene with 4-Methyl-1,3-pentadiene Promoted by Titanium Complexes Containing a Tetradentate [OSSO]-Type Bis(phenolato) Ligand

Copolymerization of ethylene with 4-methyl-1,3-pentadiene (4-MPD) catalyzed by 1,4- dithabutanediyl-linked bis(phenolato) titanium complexes 1 and 2 activated by methylaluminoxane (MAO) produced exclusively ethylene-4-MPD copolymers with high activity. The copolymer microstructure can be varied by changing the ratio between the monomers in the copolymerization feed, affording copolymers with 4-MPD content up to 83%. The resulting copolymer are crystalline as shown by thermal analysis and by the X-ray powder diffraction profiles. The microstructural features were fully elucidated by 13CNMRspectroscopy revealing that the copolymers with various 4-MPDcontent show a strong tendency to the alternating microstructure which was confirmed by the kinetic elaboration

Mechanistic Studies on Conjugated Diene Polymerizations Promoted by a Titanium Complex Containing a Tetradentate [OSSO]-Type Bis(phenolato) Ligand

A thorough experimental and theoretical mechanistic study on the conjugated dienes polymerization promoted by the postmetallocene complex dichloro{1,4-dithiabutanediy1-2,2'-bis(4,6-di-tert-butyl-phenoxytitanium, 1, activated by methylaluminoxane (MAO), is presented. Experimental polymerization studies, previously reported on butadiene, isoprene, and 4-methyl-1,3-pentadiene, have been extended to E- and Z-1,3-pentadiene polymerizations and to ethylene-1,3-pentadiene copolymerizations. Complex 1/MAO showed to be unactive in the Z-1,3-pentadiene polymerization, whereas it was quite performing toward E-1,3-pentadiene, leading to a polymer containing a mixture of 1,2- and 1,4-trans units, with a prevalence of 1,2 units at low temperatures. Also for ethylene-1,3-pentadiene copolymerizations, complex 1/MAO showed good activity. The copolymer microstructure can be varied by changing the ratio between the monomers in the copolymerization feed, affording copolymers with 1,3-pentadiene content up to 36%. Density functional theory (DFT) mechanistic studies on butadiene, E- and Z-1,3-pentadiene polymerizations indicate that monomer insertions proceed through an allylic mechanism involving a syn-eta(3) coordination of the growing chain and a s-trans-eta(2) monomer insertion

Reactivity of styrene and substituted styrenes in the presence of a homogeneous isospecific titanium catalyst

The isospecific polymerization of several para-substituted styrenes was performed in the presence of the catalyst dichloro[1,4-dithiabutanediyl-2,2'-bis(4,6-di-tert-butyl-phenoxy)]titani um activated by methylaluminoxane. All the polymers were highly regioregular and isotactic with narrow molecular weight distributions. The presence of electron-donating substituents on the aromatic ring had a positive effect on the catalyst activity, whereas electron-withdrawing substituents affected the polymerization activity negatively. Binary copolymerizations of the various substituted styrenes showed an inversion of the reactivity with respect to that observed in the homopolymerization. These results suggested that the last monomer unit of the polymer chain coordinated to the metal center, influencing the reactivity of the catalyst with respect to the incoming monomer. (c) 2006 Wiley Periodicals, Inc

[OSSO]-bisphenolate metal complexes: A powerful and versatile tool in polymerization catalysis

Since the report of the stereospecific polymerization of styrene dated 2003, metal complexes bearing [OSSO]-bisphenolate ligands have been successfully applied in different branches of homogeneous catalysis, de facto building a new research field. This review will focus on polymerization reactions promoted by these complexes, starting with those involving “traditional” monomers (such as fossil-derived olefins) up to more recent and green applications, like polymerization of terpenes or utilization of CO2 as a green building block

Metal complexes bearing sulfur-containing ligands as catalysts in the reaction of co2 with epoxides

Coupling of CO2 with epoxides is a green emerging alternative for the synthesis of cyclic organic carbonates (COC) and aliphatic polycarbonates (APC). The scope of this work is to provide a comprehensive overview of metal complexes having sulfur-containing ligands as homogeneous catalytic systems able to efficiently promote this transformation with a concise discussion of the most significant results. The crucial role of sulfur as the hemilabile ligand and its influence on the catalytic activity are highlighted as well