N-Thiocyanatosaccharin (R) was readily prepared from the sweet additive Saccharin in two steps with a 71% overall yield. By applying this new reagent to diverse nucleophiles such as benzothiophenes, indoles, oxindoles, aromatic amines, phenols, β-keto carbonyl compounds, and aromatic ketones, a novel electrophilic thiocyanation reaction was achieved with high yields (up to 99%). The potential recycling of Saccharin, the wide scope of substrates, and the mild reaction conditions made this protocol much more practical.

A new electrophilic thiocyanation reagent, N-thiocyanatophthalimide, was synthesized and applied to the first example of catalytic asymmetric electrophilic α-thiocyanation of various cyclic β-ketoesters by the bifunctional cinchona alkaloid catalysis. Thus, a variety of chiral α-thiocyanato β-ketoesters with a quaternary carbon center have been achieved in excellent yields (up to 99%) and high enantioselectivities (up to 94% ee) in a convenient manner.

The direct electrophilic α-cyanation of β-keto esters and amides has been developed using a hypervalent iodine benziodoxole-derived cyano reagent. The procedure is accomplished within 10 min and without the use of any catalyst in DMF, at room temperature. Thus, the highly functionalized quaternary carbon-centered nitriles were produced in high to excellent yields.

Techniques utilizing photo- and electrochemically induced reactions have been developed to accelerate organic processes.

as 0D and discrete, quasispherical nanoparticles with the characteristic size of less than 10 nm in shape. In the past few decades, many researchers have been intrigued by overwhelming application of CDs in fields other than solar photovoltaics, [23][24][25] semiconductor photocatalysis, [26] or light-emitting materials, [27][28][29] like in bioimaging, [30][31][32][33] drug delivery/ release, [34][35][36] theranostics, [37] and biosensing/bioassay. [38][39][40] Albeit with biological imaging agents in vitro and in vivo, heavy metals as the essential elements for the core materials of available high-performance semiconductor quantum dots (QDs) exist substantial toxicity, carcinogenic effects, and environmental hazard, even at low levels. [41][42][43][44][45] Historically, boasting the natural virtues of fascinating optical properties (e.g., up/down-conversion and excitation-dependent fluorescence emission, high fluorescence quantum yields (QY), and long fluorescence lifetime), eco-friendliness, high waterdispersible peculiarity, easy surface-functionality, low cost, highly abundant, and inexpensive raw materials, noninvasiveness, low cytotoxicity, and good biocompatibility afford CDs suitable as the elegant alternatives for toxic QDs containing heavy metals. [46][47][48][49] On the other hand, the CDs have excellent photostability against photobleaching and photoblinking as compared with the conventional organic dyes (typically fluorescein and rhodamine B). [50] In particular, multicolor CDs exhibit tunable photoluminescence by exciting the identical CDs, allowing for multimodal biophotosensitizer in biological field without interference from background autofluorescence. In this review, we aim to systematically offer a summary of preparing multicolor CDs and its various biomedical applications, mainly including for bioimaging, drug delivery/release, theranostics, and biosensing/bioassay, highlighting the complete horizons of multiplexed quantitative detection, high-resolution fluorescence imaging, and long-term, real-time monitoring of multicolor CDs.Multicolor carbon dots (CDs) as an emerging subclass of carbonaceous nanomaterials have inspired intensive attention due to the fascinating fluorogenic properties of quantum dots, exhibiting great potential applications in the biomedical field. In some cases, reported CDs with blue or green fluorescence are not desirable for further biological applications owing to the conflicting background autofluorescence, low penetration, and relatively large damage to biological tissue. However, multicolor CDs that can work in the longer wavelength region are being developed to address this issue by overcoming the autofluorescence from the cellular components (usually in the blue and green range). In this review, the development of multicolor CDs is described comprehensively, including for red-emissive or NIR-emissive CDs. Additionally, the preparation methods of multicolor CDs are summarized. Moreover, the factors affecting the luminescence of multicolor CDs are discussed in de...

The misuse of organic pollutants such as nitrofuran antibiotics (NFAs) and 2,6-dichloro-4-nitroaniline (DCN) has become a hot topic of global concern, and developing rapid, efficient, and accurate techniques for detecting NFAs and pesticides in water is a major challenge. Here, we designed a novel leadbased anion 2D metal−organic framework (MOF){[(CH 3 ) 2 NH 2 ] 2 [Pb(TCBPE)-(H 2 O) 2 ]} n (F3) with interlocking structures, in which TCBPE stands for 1,1,2,2tetra(4-carboxylbiphenyl)ethylene. Powder X-ray diffraction and thermogravimetric analysis revealed that F3 has excellent chemical and solvent stability. It is worth noting that F3 has a grinding discoloration effect. The solvent-protected grinding approach achieved F3B with a high quantum yield (QY = 73.77%) and blue fluorescence, while the direct grinding method produced F3Y with a high quantum yield (QY = 37.27%) and yellow−green fluorescence. Importantly, F3B can detect NFAs in water rapidly and sensitively while remaining unaffected by other antibiotics. F3Y can identify DCN in water quickly and selectively while remaining unchanged by other pesticides. F3B demonstrated high selectivity and rapid response to NFAs at a limit of detection (LOD) as low as 0.26 μM, while F3Y indicated high selectivity and responded quickly to DCN in water at an LOD as low as 0.14 μM. The method was successfully applied to detect NFAs in actual water samples of the fish tanks and ponds as well as the pesticide DCN in soil samples. The recovery rates were 97.0−105.15% and 102.2− 106.48%, and the relative standard deviations were 0.63−1.45% and 0.29−1.69%, respectively. In addition, F3B and F3Y can be made into fluorescent test papers for the visual detection of NFAs and DCN, respectively. Combined with experiments and density functional theory calculations, the mechanism of fluorescence quenching of MOFs by target analytes was also revealed.

The first example of catalytic asymmetric electrophilic cyanation of 3-substituted oxindoles has been achieved using readily accessible 4-acetylphenyl cyanate as the cyano source. Thus, a series of all-carbon quaternary center 3-aryl-3-cyano oxindoles were prepared using a zinc complex of a chiral pincer ligand as the catalyst in high yields (up to 95%) and excellent enantioselectivities (up to >99% ee) in the presence of 4 Å MS and 2,6-lutidine in THF at 0 °C.

A highly effective asymmetric version of α-cyanation of β-keto esters and amides was developed with a Lewis-acid catalyst. Thus, by using 10 mol % of a tridentate bisoxazoline-zinc(II) complex as the catalyst, a series of chiral nitriles containing a quaternary carbon center were obtained in excellent enantioselectivities (up to 97 % enantiomeric excess) and up to 95 % yield in the presence of 4 Å molar sieve at room temperature. For the first time, mild and active 4-acetylphenyl cyanate was used instead of cyano-hyperiodinate as the cationic cyano source for catalytic asymmetric α-cyanation.