Latest ArticlesSeveral simple, fast and practical protocols have been developed to synthesize internal or terminal propargylamines and chalcones via A3-coupling reaction of aldehydes, amines, and alkynes catalyzed by an easily available catalyst Ag2CO3 under solvent-free condition. The reaction proceeded smoothly to deliver various products in good-to-excellent yields with good functional group tolerance. Gram-scale preparation, bioactive molecule synthesis and asymmetric substrates have been demonstrated. Furthermore, plausible mechanisms for the synthesis of different products have been proposed.
By introducing a host molecule cucurbit[8]uril (CB[8]) into a charge transfer system containing an amphiphile 1-[11-(naphthalene-2-ylmethoxy)-11-oxoundecyl]pyridinium (NP) and an electron-deficient molecule methyl viologen (MV), a novel and anisotropic ternary building block was constructed by host-guest interactions, thereby leading to the morphology transformation of the final assemblies from thin-films (NP/MV complexes) into diamond-like structures (NP/MV/CB[8] complexes). These intriguing assemblies were firstly discovered and were similar with the shape of well-known metal organic frameworks (MOFs), but just comprised three small organic molecules without metal ions. This finding can enrich the shape of current supramolecular assemblies and thus contributing to more potential applications in material science.
The scandocene alkyl complex (C5Me5)2ScCH2SiMe3 was found to be an efficient catalyst for the dehydrocoupling of the non-cyclic boranes, dicyclohexylborane and thexylborane, with amines under mild conditions. The reactions afforded the corresponding aminoboranes in high yields with good functional group tolerance. The stoichiometric reaction of scandium alkyl with amine led to the isolation of a scandium amide complex, which was shown to be an active species during the catalysis. Although a borane-coordinated scandium hydride was also obtained from the stoichiometric experiment, it was not involved in the catalytic cycle. In addition, kinetic studies provided insight into this intermolecular dehydrogenation reaction.
Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) is one of the most widely used powerful explosives. The direct and selective detection of HMX, without the requirement of specialized equipment, remains a great challenge due to its extremely low volatility, unfavorable reduction potential and lack of aromatic rings. Here, we report the first chemical probe of direct identification of HMX at ppb sensitivity based on a designed metal-organic cage (MOC). The cage features two unsaturated dicopper units and four electron donating amino groups inside the cavity, providing multiple binding sites to selectively enhance host-guest events. It was found that compared to other explosive molecules the capture of HMX inside the cavity would strongly modulate the emissive behavior of the host cage, resulting in highly induced fluorescence "turn-on" (160 folds). Based on the density functional theory (DFT) simulation, the mutual fit of both size and binding sites between host and guest leads to the synergistic effects that perturb the ligand-to-metal charge-transfer (LMCT) process, which is probably the origin of such selective HMX-induced turn-on behavior.
Three carbazole derivatives, AcPTC, PxPTC and PtPTC, consisting of two 9,9-dimethyl-9,10-dihydroacridine, phenoxazine or phenothiazine donor groups and one diphenyltriazine acceptor group fixed at 1,8,9-positions of a single carbazole ring via phenylene, are designed and synthesized. X-ray diffraction analysis of AcPTC reveals that there exist multiple π-π interactions between the donor and acceptor groups to form a sandwich-like structural unit with edge-to-face interaction model. The compounds thus show obvious thermally activated delayed fluorescence with through-space charge transfer character and possess considerable photoluminescence quantum yields of up to 73% in doped films with sky-blue to yellow emissions. The solution-processed electroluminescent devices achieve the highest maximum external quantum efficiencies of 10.0%, 11% and 5.6% for AcPTC, PxPTC and PtPTC, respectively, with small efficiency roll-offs.
Herein, a facile synthesis of valuable pyrido[1,2-a]pyrimidine-4-thiones is reported via novel thiocarbonylation of C(sp3)-H bonds with carbon disulfide (CS2). This reaction features easy availability of substrates, good functional group tolerance, high yields, facile scalability and atom economy. Mechanistic investigations indicate that sulfate anion and sulfuric anhydride anion might be involved in this reaction.
Remote ether groups could be used as directing groups to prepare fully substituted 5-ether-1,2,3-triazoles with exclusive 1,5-regioselectivities and excellent chemoselectivities. Ether group could coordinate with iridium catalyst by lone-pair electron at a distance (up to four σ bonds) away from alkyne to control the regioselectivity by weak coordination effect. The cycloaddition reaction chemoselectively occurred at the propargyl ether moiety of diyne to give unique fully substituted 4-alkynyl-triazole.
Constitutionally adaptive chemistry of selenium-containing crown ethers (CEs) offers a new platform for controlling/switching the hydration of bolaamphiphile skeletons in water in an effective and simple manner by the virtue of covalent bonding. The adaptive behaviour of the macrocyclic bolaamphiphiles (transformations between C7SeBola and C7SeOBola) in response to redox environment was found to be a decisive factor.
Cu-catalyzed endo-selective asymmetric 1,3-dipolar cycloaddition of azomethine ylides with ethenesulfonyl fluorides (ESFs) was successfully developed, this protocol provided an efficient and facile method to a wide range of chiral pyrrolidine-3-sulfonyl fluorides with good to excellent results (up to 87% yield, > 20:1 dr, 94% ee). Some other chiral sulfonyl derivatives, such as sulfonamide and sulfonate, were easily accessible through simple transformations with high yields, which demonstrated that the cycloaddition products could be synthetically useful in the sulfur(Ⅵ) fluoride exchange (SuFEx) chemistry.
A visible-light-induced chemoselective reactions of quinoxalin-2(1H)-ones with alkylboronic acids in the presence of air (O2) and N2 atmosphere was developed under transition-metal free conditions, providing 3-alkylquinoxalin-2(1H)-ones and 3, 4-dihydroquinoxalin-2(1H)-ones, respectively. The overall strategy accommodates a broad scope of substituted quinoxalin-2(1H)-ones and alkylboronic acids with good to excellent product yields.
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