Introduction of polar comonomers into polyethylene is highly challenging,paving the way to tuning the copolymers'mechanical properties,adhesion/compatibility,and biodegradability.Polar-group tolerant single-site p...Introduction of polar comonomers into polyethylene is highly challenging,paving the way to tuning the copolymers'mechanical properties,adhesion/compatibility,and biodegradability.Polar-group tolerant single-site palladium and,more tempting,nickel-based catalysts have demon-strated promising reactivities in the ethylene copolymerization with polar comonomers via coordination/insertion mechanism。展开更多
This review article surveys the recent experimental findings that suggest alternative chemical models of directed chirality amplification at the early,prebiotic Earth.It is believed that the chirality amplification st...This review article surveys the recent experimental findings that suggest alternative chemical models of directed chirality amplification at the early,prebiotic Earth.It is believed that the chirality amplification step followed the initial emergence of small enantiomeric imbalance and preceded(as a necessary condition)the occurrence of homochiral biopolymers,assembled from enantiomerically pure building blocks.This work focuses on the chemical nature of possible mechanisms of primordial chirality enhancement,without going into detail of the preceding and subsequent phases of origination of biological homochirality and life on Earth.These mechanisms are discussed through the prism of integrity of biological natural selection and chemical kinetic selection.展开更多
Oxidative kinetic resolution of 1-phenylethanol in the presence of manganese complexes,bearing conformationally nonrigid achiral bis-amine-bis-pyridine ligands,in the absence of any exogenous chiral additives,is repor...Oxidative kinetic resolution of 1-phenylethanol in the presence of manganese complexes,bearing conformationally nonrigid achiral bis-amine-bis-pyridine ligands,in the absence of any exogenous chiral additives,is reported.The only driving force for the chiral discrimination is the small initial enantiomeric imbalance of the scalemic(nonracemic)substrate:the latter dynamically controls the chirality of the catalyst,serving itself as the chiral auxiliary.In effect,the ee of 1-phenylethanol increases monotonously over the reaction course.This dynamic control of catalyst chirality by the substrate has been unprecedented;a consistent kinetic model for this process is presented.The reported catalyzed substrate self-enantioenrichment mechanism is discussed in relation to the problem of prebiotic chirality amplification.展开更多
Since the milestone discovery of Ni(II)salicylaldiminate catalysts by Grubbs and co-workers[1],nickel(II)complexes with N,N-and N,O-donor ligands have strengthened their lead in the search for highly active platforms ...Since the milestone discovery of Ni(II)salicylaldiminate catalysts by Grubbs and co-workers[1],nickel(II)complexes with N,N-and N,O-donor ligands have strengthened their lead in the search for highly active platforms for olefins homo-and copolymerization with various co-monomers,including those with polar groups,to achieve polymers with precisely controlled microstructures[2,3].展开更多
文摘Introduction of polar comonomers into polyethylene is highly challenging,paving the way to tuning the copolymers'mechanical properties,adhesion/compatibility,and biodegradability.Polar-group tolerant single-site palladium and,more tempting,nickel-based catalysts have demon-strated promising reactivities in the ethylene copolymerization with polar comonomers via coordination/insertion mechanism。
基金The author thanks the Russian Science Foundation(#20-13-00032)for financial support.
文摘This review article surveys the recent experimental findings that suggest alternative chemical models of directed chirality amplification at the early,prebiotic Earth.It is believed that the chirality amplification step followed the initial emergence of small enantiomeric imbalance and preceded(as a necessary condition)the occurrence of homochiral biopolymers,assembled from enantiomerically pure building blocks.This work focuses on the chemical nature of possible mechanisms of primordial chirality enhancement,without going into detail of the preceding and subsequent phases of origination of biological homochirality and life on Earth.These mechanisms are discussed through the prism of integrity of biological natural selection and chemical kinetic selection.
基金The authors thank the Ministry of Science and Higher Education of the Russian Federation(projects AAAA-A17-117041710080-4 and AAAA-A17-117041710078-1)RVO and KPB acknowledge financial support from the Russian Foundation for Basic Research,grant 18-33-20078AAB thanks the Siberian Supercomputer Center SB RAS.In this study,the equipment of the Center of Collective Use“National Center of Catalysis Research”and of the MultiAccess Chemical Service Center has been used.
文摘Oxidative kinetic resolution of 1-phenylethanol in the presence of manganese complexes,bearing conformationally nonrigid achiral bis-amine-bis-pyridine ligands,in the absence of any exogenous chiral additives,is reported.The only driving force for the chiral discrimination is the small initial enantiomeric imbalance of the scalemic(nonracemic)substrate:the latter dynamically controls the chirality of the catalyst,serving itself as the chiral auxiliary.In effect,the ee of 1-phenylethanol increases monotonously over the reaction course.This dynamic control of catalyst chirality by the substrate has been unprecedented;a consistent kinetic model for this process is presented.The reported catalyzed substrate self-enantioenrichment mechanism is discussed in relation to the problem of prebiotic chirality amplification.
基金the program AAAA-A17-117041710085-9 for the Boreskov Institute of Catalysis.
文摘Since the milestone discovery of Ni(II)salicylaldiminate catalysts by Grubbs and co-workers[1],nickel(II)complexes with N,N-and N,O-donor ligands have strengthened their lead in the search for highly active platforms for olefins homo-and copolymerization with various co-monomers,including those with polar groups,to achieve polymers with precisely controlled microstructures[2,3].
