24 research outputs found
Synthesis of Poly(arylenevinylene)s by Rhodium-Catalyzed Stitching Polymerization/Alkene Isomerization
Poly(arylenevinylene)s constitute an important class
of π-conjugated
polymers for their potential utility as optoelectronic materials.
Herein, we developed a sequence of rhodium-catalyzed stitching polymerization
of 1,2-dialkynyl(hetero)arenes and aromatization-driven alkene isomerization
for the synthesis of new poly(arylenevinylene)s. The polymerization
and subsequent alkene isomerization proceeded smoothly with high degree
of stitching efficiency by employing a Rh/tfb complex as the catalyst,
and not only diynes but also triynes and tetraynes could be polymerized
to give poly(arylenevinylene)s that are not easily accessible by existing
synthetic methods. The polymers obtained by the present method were
thermally stable, and their optical properties could be varied depending
on the repeating unit structure
Copper-Catalyzed Hydroboration of Carbon Dioxide
A copper/N-heterocyclic
carbene catalyzed hydroboration of carbon
dioxide has been developed to give a formic acid derivative selectively
under mild conditions. Investigations directed toward understanding
the catalytic cycle of this process have been carried out, and the
hydroboration product can be directly used as a formylation reagent
for various amines
Rhodium-Catalyzed Stitching Reaction: Convergent Synthesis of Quinoidal Fused Oligosiloles
Quinoidal fused oligosiloles, a new
family of silicon-bridged π-conjugated
compounds, have been synthesized for the first time based on a new
synthetic strategy, a stitching reaction. Multiple carbon–carbon
bonds can be formed consecutively between two oligo(silylene-ethynylene)s
under rhodium catalysis in a stitching manner, and up to five siloles
have been fused in a quinoidal form. Physical properties of these
oligosiloles have also been investigated to find a unique trend in
their LUMO levels, which become higher with longer π-conjugation
Rhodium-Catalyzed Polymerization of 3,3-Diarylcyclopropenes Involving a 1,4-Rhodium Migration
A new mode of metal-catalyzed polymerization
reaction has been
developed by exploiting the ability of 1,4-rhodium migration of an
organorhodium(I) species. Specifically, it has been demonstrated that
3,3-diarylcyclopropenes undergo polymerization through an insertion–1,4-rhodium
migration sequence by using an arylrhodium(I) initiator/catalyst to
give poly(cyclopropylene-<i>o</i>-phenylene)s, which are
difficult to synthesize by conventional polymerization methods
Rhodium-Catalyzed Stitching Reaction: Convergent Synthesis of Quinoidal Fused Oligosiloles
Quinoidal fused oligosiloles, a new
family of silicon-bridged π-conjugated
compounds, have been synthesized for the first time based on a new
synthetic strategy, a stitching reaction. Multiple carbon–carbon
bonds can be formed consecutively between two oligo(silylene-ethynylene)s
under rhodium catalysis in a stitching manner, and up to five siloles
have been fused in a quinoidal form. Physical properties of these
oligosiloles have also been investigated to find a unique trend in
their LUMO levels, which become higher with longer π-conjugation
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Palladium-Catalyzed Desymmetrization of Silacyclobutanes with Alkynes: Enantioselective Synthesis of Silicon-Stereogenic 1-Sila-2-cyclohexenes and Mechanistic Considerations
A palladium-catalyzed enantioselective desymmetrization of silacyclobutanes with alkynes has been developed to give silicon-stereogenic 1-sila-2-cyclohexenes with high enantioselectivity. The products thus obtained undergo further derivatizations with complete stereoselectivity, and a new catalytic cycle involving alkyne coordination (oxidative cyclization)–transmetalation (σ-bond metathesis)–reductive elimination has also been proposed
Palladium-Catalyzed Desymmetrization of Silacyclobutanes with Alkynes: Enantioselective Synthesis of Silicon-Stereogenic 1-Sila-2-cyclohexenes and Mechanistic Considerations
A palladium-catalyzed enantioselective desymmetrization of silacyclobutanes with alkynes has been developed to give silicon-stereogenic 1-sila-2-cyclohexenes with high enantioselectivity. The products thus obtained undergo further derivatizations with complete stereoselectivity, and a new catalytic cycle involving alkyne coordination (oxidative cyclization)–transmetalation (σ-bond metathesis)–reductive elimination has also been proposed
Palladium-Catalyzed Synthesis of 4-Oxaspiro[2.4]heptanes via Central Attack of Oxygen Nucleophiles to π-Allylpalladium Intermediates
A palladium-catalyzed decarboxylative cyclopropanation of γ-methylidene-δ-valerolactones with aromatic aldehydes has been developed to give 4-oxaspiro[2.4]heptanes with high selectivity. The site of nucleophilic attack to a π-allylpalladium intermediate has been controlled with a sterically demanding phosphine ligand. The course of the reaction is highly dependent on ligands and solvents, and selective formation of methylenetetrahydropyrans has also been realized
Intermolecular Three-Component Arylsilylation of Alkynes under Palladium/Copper Cooperative Catalysis
An intermolecular
three-component arylsilylation of alkynes has
been developed under mild palladium/copper cooperative catalysis.
The reaction proceeds through <i>syn</i>-addition of an
aryl group and a silyl group across the carbon–carbon triple
bond of an alkyne. This represents the first transition-metal-catalyzed
fully intermolecular arylsilylation of alkynes, and transformations
of the resulting products have also been demonstrated