138 research outputs found
Self-Buffering Organocatalysis Tailoring Alternating Polyester
A major success has
been made on organocatalytic ring-opening alternating
copolymerization (ROAP) of phthalic anhydride and ethylene oxide (EO)
by use of a simple phosphazene base (<i>t</i>-BuP<sub>1</sub>). Polyesters with perfectly alternating sequence distribution, controlled
molar masses, and low dispersities (<i>Ä</i><sub>M</sub> < 1.1) are obtained. The ROAP exhibited a distinct living nature
so that block, nonlinear, end-functional structures and postpolymerization
modification of the alternating polyesters are readily achieved. Solvent,
excess EO, and catalyst can be effortlessly recovered and reused.
The ideally suitable basicity of <i>t</i>-BuP<sub>1</sub> is considered crucial for the high selectivity and neatness of the
ROAP, which engenders a self-buffering mechanism rendering the carboxy
and hydroxy terminals appropriately active to allow chain growth in
an strictly alternating manner and complete avoidance of side reactions
(epoxide self-propagation, transesterification) even at full conversion
of the anhydride
Calcium-Mediated CâH and CâF Bond Cleavage: Synthesis of Indenes and Perfluorodibenzopentalenes from 1,4-Dilithio-1,3-butadienes
The
development of Ca-mediated reactions is of great importance
and is in great demand in both organometallic and organic chemistry.
In this paper, we report that calcium iodide efficiently promotes
the transformation of various 1,4-dilithio-1,3-butadienes into indenes
or perfluorodibenzopentalenes, via an intramolecular CâH or
CâF bond cleavage, respectively. In the reaction process, the
Ca-induced s-<i>cis/trans</i> configurational isomerization
of 1,4-dilithio-1,3-butadienes is followed by the subsequent nucleophilic
CâH or CâF bond activation
Supplementary_Table_of_SSR_marker_for_Halenia_elliptica â Supplemental material for Transcriptome Analysis and Microsatellite Markers Development of a Traditional Chinese Medicinal Herb Halenia elliptica D. Don (Gentianaceae)
<p>Supplemental material, Supplementary_Table_of_SSR_marker_for_Halenia_elliptica for Transcriptome Analysis and Microsatellite Markers Development of a Traditional Chinese Medicinal Herb Halenia elliptica D. Don (Gentianaceae) by Mingliu Yang, Nanyu Han, Heng Li and Lihua Meng in Evolutionary Bioinformatics</p
Calcium-Mediated CâH and CâF Bond Cleavage: Synthesis of Indenes and Perfluorodibenzopentalenes from 1,4-Dilithio-1,3-butadienes
The
development of Ca-mediated reactions is of great importance
and is in great demand in both organometallic and organic chemistry.
In this paper, we report that calcium iodide efficiently promotes
the transformation of various 1,4-dilithio-1,3-butadienes into indenes
or perfluorodibenzopentalenes, via an intramolecular CâH or
CâF bond cleavage, respectively. In the reaction process, the
Ca-induced s-<i>cis/trans</i> configurational isomerization
of 1,4-dilithio-1,3-butadienes is followed by the subsequent nucleophilic
CâH or CâF bond activation
Synthesis, Structural Characterization, and Reactivity of a Fluorene-Based Calcium Oxycyclopentadienide Complex
Direct
deprotonation of 9-fluorenol with CaÂ[NÂ(SiMe<sub>3</sub>)<sub>2</sub>]<sub>2</sub> efficiently generated a fluorene-based calcium
oxycyclopentadienide complex, which is the first alkaline earth metal
complex containing an oxycyclopentadienyl dianion ligand. The Ρ<sup>5</sup>, Ρ<sup>1</sup>, and Ρ<sup>2</sup> interactions
between the oxycyclopentadienyl dianion ligand and the calcium center
were observed in the solid state. The calcium oxycyclopentadienide
complex displayed reductive character and multiple reactive sites.
Its reactivity toward a range of electrophiles, especially acid chlorides,
was investigated and discussed in detail. A wide variety of fluorene
derivatives were synthesized
Well-Defined and Structurally Diverse Aromatic Alternating Polyesters Synthesized by Simple Phosphazene Catalysis
Alcohol-initiated
ring-opening alternating copolymerization (ROAP)
of phthalic anhydride (PA) and a variety of mono-, di-, and trisubstituted
epoxides has been performed with a weak phosphazene base (<i>t</i>-BuP<sub>1</sub>) as the catalyst. Each product exhibits
a perfectly alternating sequence distribution, controlled molar mass
(<i>M</i><sub>n</sub> up to 124 kg mol<sup>â1</sup>), and low dispersity (<i>Ä</i><sub>M</sub> <
1.15, mostly). Full conversion of PA can be reached in 0.5â24
h depending on the substituent of the epoxide, the targeted degree
of polymerization, and the amount of <i>t</i>-BuP<sub>1</sub> used (0.2â5 mol % of PA) when the reactions are conducted
under solvent-free conditions at 100 °C with a small excess of
the epoxide (0.5 equiv of PA). The glass transition temperature of
the polyester ranges from â14 to 135 °C. The living nature
of the ROAP allows one-pot construction of well-defined block-alternating
copolymers through sequential addition of two epoxides. Statistical-alternating
copolymers have also been synthesized by copolymerization of PA and
two mixed epoxides. Thus, the structural diversity of aromatic alternating
polyesters synthesized by this simple organocatalysis has been largely
enriched
Additional file 1: of Associations of LBX1 gene and adolescent idiopathic scoliosis susceptibility: a meta-analysis based on 34,626 subjects
Table S1. Genotype and allele distribution of LBX1 polymorphisms in AIS cases and controls. Figure S1. X-ray of an AIS patient. Figure S2. Flow chart of data selection. Figure S3. Beggâs funnel plot for publication bias in the dominant model for rs111090870 polymorphism. Figure S4. Beggâs funnel plot for publication bias in the dominant model for rs678741 polymorphism. Figure S5. Beggâs funnel plot for publication bias in the dominant model for rs11598564 polymorphism. Figure S6. Beggâs funnel plot for publication bias in the dominant model for rs625039 polymorphism. (DOCX 144 kb
Cu(II)-Based MetalâOrganic Framework Loaded with Silver Nanoparticles as a Catalyst for the A<sup>3</sup>âCoupling Reaction
The
embedding of metal nanoparticles (NPs) in metalâorganic
frameworks (MOFs) has attracted a wide range of attention in the field
of catalysis due to the high agglomeration resistance of NPs in MOFs.
In this work, a Cu(II)-based MOF with the formula {[Cu1.5(TPA)(BIBT)]¡4DMF¡6H2O]}n (1) (H3TPA = tris(4â˛-carboxybiphenyl)amine;
BIBT = 4,7-di(1H-imidazol-1-yl)benzo[c][1,2,5]thiadiazole;
and DMF = N,N-dimethylformamide) was synthesized
under solvothermal condition. Structural analysis revealed that Cu-MOF 1 possessed 3-fold interpenetrated three-dimensional (3D)
coordination frameworks with large one-dimensional (1D) channels along
the a-axis. Due to the interaction between Ag and
S/N, Ag NPs could be encapsulated into the pores of Cu-MOF 1 to generate Ag NPs and MOF composites, xAg/1 (x = 0.3, 0.5, 0.8, and x was
the molar ratios of AgNO3 with Cu-MOF 1 in
the synthesis), which was further demonstrated by powder X-ray diffraction,
Fourier transform infrared, scanning electron microscopy, transmission
electron microscope, energy dispersive spectrometer, X-ray photoelectron
spectroscopy, and BrunauerâEmmettâTeller (BET) analysis.
In addition, synthesized 0.5Ag/1 exhibited outstanding
catalytic activity for the A3-coupling reaction of aldehyde,
alkyne, and amine with high recyclability. This work presents a viable
strategy for using Cu(II)-based MOF loading with Ag NPs as heterogeneous
catalysts for the A3-coupling reaction
Admixture dates for Europeans.
<p>The table gives the admixture dates for Europeans. For East Asians we obtain Îťâ=â1,253â1,287, although no valid conversion to <i>t<sub>GF</sub></i> is possible without an East Asian pedigree map and hence we focus on the results for Europeans in this study.</p
Cu(II)-Based MetalâOrganic Framework Loaded with Silver Nanoparticles as a Catalyst for the A<sup>3</sup>âCoupling Reaction
The
embedding of metal nanoparticles (NPs) in metalâorganic
frameworks (MOFs) has attracted a wide range of attention in the field
of catalysis due to the high agglomeration resistance of NPs in MOFs.
In this work, a Cu(II)-based MOF with the formula {[Cu1.5(TPA)(BIBT)]¡4DMF¡6H2O]}n (1) (H3TPA = tris(4â˛-carboxybiphenyl)amine;
BIBT = 4,7-di(1H-imidazol-1-yl)benzo[c][1,2,5]thiadiazole;
and DMF = N,N-dimethylformamide) was synthesized
under solvothermal condition. Structural analysis revealed that Cu-MOF 1 possessed 3-fold interpenetrated three-dimensional (3D)
coordination frameworks with large one-dimensional (1D) channels along
the a-axis. Due to the interaction between Ag and
S/N, Ag NPs could be encapsulated into the pores of Cu-MOF 1 to generate Ag NPs and MOF composites, xAg/1 (x = 0.3, 0.5, 0.8, and x was
the molar ratios of AgNO3 with Cu-MOF 1 in
the synthesis), which was further demonstrated by powder X-ray diffraction,
Fourier transform infrared, scanning electron microscopy, transmission
electron microscope, energy dispersive spectrometer, X-ray photoelectron
spectroscopy, and BrunauerâEmmettâTeller (BET) analysis.
In addition, synthesized 0.5Ag/1 exhibited outstanding
catalytic activity for the A3-coupling reaction of aldehyde,
alkyne, and amine with high recyclability. This work presents a viable
strategy for using Cu(II)-based MOF loading with Ag NPs as heterogeneous
catalysts for the A3-coupling reaction
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