摘要 :
During last two decades,transition-metal catalyzed asymmetric reactions under continuous flow system have attracted a widespread attention.With its prominent advantages including higher safety and efficiency,precise control,better...
展开
During last two decades,transition-metal catalyzed asymmetric reactions under continuous flow system have attracted a widespread attention.With its prominent advantages including higher safety and efficiency,precise control,better heat/mass transfer,easier scale-up and better sustainability,it has impressed both the academia and related industries.However,comparing with the prosperous development of transition-metal catalyzed asymmetric reactions in batch,utilization of this type of chemistry under continuous flow is still at an early stage.To inspire more potential industrial application and further studies of this chemistry in flow,this review sum-marized the recent advances of transition-metal catalyzed asymmetric reactions under continuous flow.Moreover,we further discussed the encountered challenges including reactor engineering,catalyst design,catalyst deacti-vation,pressure drop,clogging,side reactions etc.,as well as their corresponding solutions and achievements in this mini-review.
收起
摘要 :
@@ 1Introduction
It is well known the ability of primary and secondary nitroalkanes to generate carbanions (under basic conditions) strongly stabilized by the electron-withdrawing effect of the nitro group[1-4]. Thus, the main us...
展开
@@ 1Introduction
It is well known the ability of primary and secondary nitroalkanes to generate carbanions (under basic conditions) strongly stabilized by the electron-withdrawing effect of the nitro group[1-4]. Thus, the main use of nitroalkanes is devoted to the generation of new carbon-carbon bonds through two principal approaches (Scheme 1): (i) reaction with carbonyl derivatives (nitroaldol-Henry-reaction), and (ii) Michael addition to electron poor alkenes.
收起
摘要 :
A ’H NMR signal shifted drastically to down field (δ - 10.0) at the bay area and in dose proximity to C = O group for H-1 was observed through complete assignments of 1H NMR spectra for pyridino- and benzobenzanthrones. It is co...
展开
A ’H NMR signal shifted drastically to down field (δ - 10.0) at the bay area and in dose proximity to C = O group for H-1 was observed through complete assignments of 1H NMR spectra for pyridino- and benzobenzanthrones. It is concluded that this phenomenon is due not only to the anisotropy effect of C=O plus aromatic ring current effect, but also to the electrostatic attraction of C-H (δ+)…O(δ-)=C interaction. The evidence for the sp2C-H…O = C intramolecular interaction similar to hydrogen bond has also been given by EI-MS and MS/MS (CID) spectroscopy and IR spectroscopy, as well as MNDO-PM3 calculations. This new kind of interaction might be called ’quasi-hydrogen bond’.
收起
摘要 :
Comprehensive Summary,Carbon dots(CDs)are an emerging class of nanomaterials with intriguing photophysical properties.Recently,achieving room temperature phosphorescence(RTP)for CDs has attracted considerable attention for biomedi...
展开
Comprehensive Summary,Carbon dots(CDs)are an emerging class of nanomaterials with intriguing photophysical properties.Recently,achieving room temperature phosphorescence(RTP)for CDs has attracted considerable attention for biomedical and information applications.However,the CDs based RTP materials generally require the use of polymeric and inorganic matrix to provide the rigid environments,which remains a great challenge to obtain matrix-free CDs with RTP.Herein,a novel supramolecular strategy based on strong interparticle interactions has been developed to attain this objective,by covalent decoration of ureido-pyrimidinone(UPy,a multiple hydrogen bonding unit)on the surface of CDs.Structural characterizations validated the core-shell structure of the as-prepared CDs(EDTA-CDs)and demonstrated the successful attachment of UPy via post-modification(UPy-CDs).The presence of UPy recognition units render the strong hydrogen bonding between UPy-CDs,which stabilizes the triplet state via rigidifying effect.As a result,UPy-CDs exhibit matrix-free efficient RTP(λ_(em)=534 nm)with high brightness and long lifetime(33.6 ms)in the solid state.Owing to the dual-emission character,we further explored the application potential of UPy-CDs in information encryption and anti-counterfeiting.Overall,this work provides a new and facile strategy for achieving matrix-free phosphorescent CDs with elegant incorporation of supramolecular chemistry.
收起
摘要 :
Elasticity,as an emerging phenomenon of crystals,endows the newfangled properties on crystals owing to the altered local crystallinity in the deformed state,and hence attracts increasing research endeavors.However,only a few molec...
展开
Elasticity,as an emerging phenomenon of crystals,endows the newfangled properties on crystals owing to the altered local crystallinity in the deformed state,and hence attracts increasing research endeavors.However,only a few molecular crystals and a limited number of one-dimensional coordination polymer crystals have exhibited such fantastic elastic response under mechanical stress.Herein,we report the first example of elastic hydrogen-bonded ionic framework(HIF)of{(CN_(3)H_(6))_(2)[Ti(μ_(2)-O)(SO_(4))_(2)]}n,assembled from one-dimensional negatively charged inorganic[Ti(μ_(2)-O)(SO_(4))_(2)]n 2n-chains and positively charged organic guanidinium cations via hydrogen bonds and electrostatic interactions.The slender prismatic single crystal exhibits remarkable elasticity with an optimal elastic bending strain(ε)of 2.5%.Impressively,the crystals give rise to two-dimensional elasticity owing to the equivalent crystallographic planes of the exposed faces and an unusual elastic response at liquid nitrogen temperature.The in-depth crystallographic analyses reveal hydrogen bonds and electrostatic interactions between anion chains and cations function like adhesive glue and account for such specific elastic properties,owing to the flexible and dynamic attributes of hydrogen bonds as they can work in a range of distance and orientation.And the channel in HIF provides space for bending with reduced strain.Incorporating these factors into low-dimensional crystals could be a general guidance for designing elastic crystals.Elasticity ganged with other intrinsic properties of HIF materials could inspire their newfangled applications in the near future.
收起
摘要 :
@@ 1Introduction
Carbon-carbon bond formation reactions are highly important in organic chemistry, because these reactions may be used to construct complicated molecules. Samarium diiodide is known to be a one-electron reducing a...
展开
@@ 1Introduction
Carbon-carbon bond formation reactions are highly important in organic chemistry, because these reactions may be used to construct complicated molecules. Samarium diiodide is known to be a one-electron reducing agent and recently used in many organic reactions. A radicals is postulated as an intermediate, which may be formed by direct reduction of halides, carbonyls and other functional groups.
收起
摘要 :
The co-crystallization of tetra-iso-butyl-resorcin[4]arene 1 and 2,6-diacetyl- pyridine (Ac2py) from MeCN/CH2Cl2 yielded a multi-component complex 1(Ac2py(2H2O(0.5Me-CN 2, in which the upper rim of 1 is extended supramolecularly b...
展开
The co-crystallization of tetra-iso-butyl-resorcin[4]arene 1 and 2,6-diacetyl- pyridine (Ac2py) from MeCN/CH2Cl2 yielded a multi-component complex 1(Ac2py(2H2O(0.5Me-CN 2, in which the upper rim of 1 is extended supramolecularly by way of hydrogen bonds. Complex 2 (C52H66.5N1.5O14) crystallizes in monoclinic, space group P21/m with a = 10.845(9), b = 20.805(17), c = 12.881(11) (A), β = 103.884(19)o, V = 2821(4) (A)3, Dc = 1.102 g/cm3 and Z = 2. The molecular structure shows that the two adjacent double-stranded arrays as well as linear and zigzag chains generated from Ac2py and water bridging to two resorcin[4] arene molecules, respectively, facilitate self-inclusion of one-dimensional hydrogen-bonded polymer.
收起
摘要 :
A new photochromic organic compound of thiosemicarbazone, 4-(p-bromo-α-methylaminothiocarbonyl hydrazonobenzal)-2,5-dihydro-3-methyl-5-oxo-l-phenyl pyrazole, was synthesized and characterized by elemental analyses, IR, 1H NMR spe...
展开
A new photochromic organic compound of thiosemicarbazone, 4-(p-bromo-α-methylaminothiocarbonyl hydrazonobenzal)-2,5-dihydro-3-methyl-5-oxo-l-phenyl pyrazole, was synthesized and characterized by elemental analyses, IR, 1H NMR spectra, and X-ray single-crystal diffraction analysis. The compound exhibited an interesting photochromism in the solid state when irradiated by ultraviolet light at 365 nm. The photochromic kinetics was studied by the time-dependent powder UV-Vis reflectance spectra. The intermolecular and intramolecular hydrogen-bonding interactions may be responsible for the photochromic phenomenon.
收起
摘要 :
The interactions of HF, H2O and NH3 with Br2 are investigated at the MP2(full)/ aug-cc-pVDZ level. It is found that two kinds of stable complexes, halogen-bonded and hydrogen- bonded complexes, exist between Br2 and HF and between...
展开
The interactions of HF, H2O and NH3 with Br2 are investigated at the MP2(full)/ aug-cc-pVDZ level. It is found that two kinds of stable complexes, halogen-bonded and hydrogen- bonded complexes, exist between Br2 and HF and between Br2 and H2O. The interaction energy analysis and natural population analysis (NPA) are conducted to these two kinds of complexes, indicating the halogen-bonded complexes are more stable than the corresponding hydrogen-bonded ones, and the binding energies of the former increase in the order HF＜H2O＜NH3, different from HF＞H2O for the latter.
收起
摘要 :
Two new inclusion 1,4-butylenediphosphonates with three-dimensional hydrogenbonded frameworks have been synthesized and determined by single-crystal X-ray diffraction. In compound 1, the two-dimensional cationic substructures inte...
展开
Two new inclusion 1,4-butylenediphosphonates with three-dimensional hydrogenbonded frameworks have been synthesized and determined by single-crystal X-ray diffraction. In compound 1, the two-dimensional cationic substructures interpenetrate into the anionic framework, and in compound 2, the cations are encapsulated in the three-dimensional framework. Crystal 1 (C14H24N2O8P2) belongs to triclinic, space group Pī with a = 9.4645(2), b = 9.6490(2), c = 11.9479(3)A, α = 79.7420(10), β = 73.5650(10),γ= 63.8420(10)o, V = 937.55(4) A3, Z = 2, Mr = 410.29, Dc = 1.453 g/cm3,μ(MoKα) = 0.276 mm-1, F(000) = 432, the final R = 0.0465 and wR = 0.1304 for 3274 independent reflections. Crystal 2 (C18H26N2O10P2) is of monoclinic, space group P21/c with a = 9.7069(12), b = 16.227(2), c = 6.9339(9) A, β = 98.834(3)o, V = 1079.2(2) A3, Z = 2, Mr = 492.35, Dc = 1.515 g/cm3, μ(MoKα) = 0.261 mm-1, F(000) = 516, the final R = 0.0611 and wR = 0.1162 for 1871 independent reflections.
收起
