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Identifying the missing link in catalyst transfer polymerization.

ABSTRACT: Nickel-catalyzed catalyst transfer polycondensation (CTP) of thiophenes is an efficient strategy for the controlled synthesis of polythiophenes. However, a detailed view of its reaction mechanism has remained elusive with unresolved questions regarding the geometry and bonding of critical Ni(0) thiophene intermediates. Herein, we provide experimental and computational evidence of structurally characterized square planar ?2-Ni(0)-thiophene species and their relevance to the mechanism of CTP. These results confirm the viability of C,C-?2 bound intermediates in CTP of thiophenes, providing an electronic rationale for the stability of such species, and thus that such processes can proceed as living polymerizations. We further show that C,S-?2 species may also be relevant in nickel-catalyzed CTP of thiophenes, providing new avenues for exploitation and optimization.

SUBMITTER: He W

PROVIDER: S-EPMC6155128 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature

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Identifying the missing link in catalyst transfer polymerization.

He Weiying W Patrick Brian O BO Kennepohl Pierre P

Nature communications 20180924 1

Nickel-catalyzed catalyst transfer polycondensation (CTP) of thiophenes is an efficient strategy for the controlled synthesis of polythiophenes. However, a detailed view of its reaction mechanism has remained elusive with unresolved questions regarding the geometry and bonding of critical Ni(0) thiophene intermediates. Herein, we provide experimental and computational evidence of structurally characterized square planar η<sup>2</sup>-Ni(0)-thiophene species and their relevance to the mechanism o ...[more]

PMID: 30250037

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Project description:The origin and deep evolution of retroviruses remain largely unclear. It has been proposed that retroviruses might have originated from a Ty3/Gypsy retrotransposon, but all known Ty3/Gypsy retrotransposons are only distantly related to retroviruses. Retroviruses and some plant Athila/Tat elements (within Ty3/Gypsy retrotransposons) independently evolved a dual RNase H domain and an env/env-like gene. Here, we reported the discovery of a novel lineage of retrotransposons, designated Odin retrotransposons, in the genomes of eight sea anemones (order Actinaria) within the Cnidaria phylum. Odin retrotransposons exhibited unique genome features, encoding a dual RNase H domain (like retroviruses) but no env gene (like most Ty3/Gypsy retrotransposons). Phylogenetic analyses based on reverse transcriptase showed that Odin retrotransposons formed a sister group to lokiretroviruses, and lokiretroviruses and Odin retrotransposons together were sister to canonical retroviruses. Moreover, phylogenetic analyses based on RNase H and integrase also supported the hypothesis that Odin retrotransposons were sisters to lokiretroviruses. Lokiretroviruses and canonical retroviruses did not form a monophyletic group, indicating that lokiretroviruses and canonical retroviruses might represent two distinct virus families. Taken together, the discovery of Odin retrotransposons narrowed down the evolutionary gaps between retrotransposons and canonical retroviruses and lokiretroviruses. IMPORTANCE The origin of retroviruses remains largely unclear. In this study, we discovered a novel retrotransposon lineage, Odin retrotransposons, within the genomes of sea anemones (order Actinaria). In contrast to retroviruses and most retrotransposons, Odin retrotransposons encode a dual RNase H domain but no env gene. Phylogenetic analyses showed that Odin retrotransposons were sisters to lokiretroviruses, and lokiretroviruses and Odin retrotransposons were sisters to retroviruses, establishing an evolutionary framework to decipher the origin of retroviruses (canonical retroviruses and lokiretroviruses). Our results provided insights into the diversity and deep evolution of LTR retrotransposons closely related to retroviruses.

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Identifying the missing link in catalyst transfer polymerization.

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Identifying the missing link in catalyst transfer polymerization.

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