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A heptamethine cyanine-based near-infrared (NIR) fluorescent probe Cy-1 for hydrosulfide detection was developed, with the response mechanism based on nucleophilic substitution of acryloyl moiety by HS−. Upon addition of NaHS, Cy-1 displayed a rapid fluorescence quenching (excited at 700 nm) and a quick fluorescence enhancement (excited at 544 nm) as well as obvious changes in absorption spectra and color. The response was fast within tens of seconds and could be observed by naked eyes. By contrasting Cy-1 with the reported probe CyAC, the superiority of Cy-1 in selectivity over Cys was demonstrated. Besides, it also exhibited excellent selectivity and sensitivity to HS− over various anions (0.33-μM detection limit). Additionally, this probe was successfully applied in fetal bovine serum samples and imaging of hydrosulfide in living cells.

A facile and efficient method for reductive N-alkylation of nitrobenzenes with alcohols catalyzed by the bimetallic catalyst Cu30Cr5/γ-Al2O3, in a fixed-bed reactor, was successfully established. X-ray diffraction, temperature-programmed reduction, and X-ray photoelectron spectroscopy were used to characterize the catalyst. Introduction of Cr to Cu30/γ-Al2O3 was found to substantially enhance the dispersion of Cu0 particles, which are believed to be the active sites for the reductive N-alkylation. The reaction conditions were optimized and a series of alcohols and nitrobenzenes were converted into N-alkylated anilines in more than 90 % yield by use of this catalyst.

The ring-opening reaction of aziridine with alkylamines over a series of ion-exchange resins was investigated. Among these catalysts, D001-CC exhibited excellent catalytic performance. The catalysts were characterized by SEM and N2 adsorption–desorption. The results indicated that the selectivity of N,N-diethylethylenediamine mainly depended on the acidity and S BET of the resins. Strong Bronsted acid sites played an important role on the conversion of aziridine, and the distribution of acid sites on catalyst had a significant effect on the selectivity of N,N-diethylethylenediamine. The reaction parameters, such as reaction time, molar ratio, reaction temperature, and catalyst loading, were also optimized and N,N-diethylethylenediamine was obtained in an excellent yield of 97 %. Furthermore, D001-CC was efficiently recycled five times by simple treatment with large amounts of deionized water and mineral acid. Finally, a series of asymmetric ethylenediamine derivatives were successfully synthesized with this method. Therefore, a simple and versatile process for the synthesis of asymmetric ethylenediamine derivatives has been established over ion-exchange resins.

An impurity was detected in the roflumilast product which was supposed to be N-(3,5-dichloropyridin-4-yl)-4-difluoromethoxy-3-methoxybenzamide. To further verify the impurity structure, this compound was synthesized from 4-difluoromethoxy-3-hydroxybenzaldehyde through O-alkylation, oxidation, chlorination, and amidation reaction and characterized by 1H NMR, 13C NMR, and HPLC–MS. Comparison of the HPLC–MS spectrum of the impurity and the synthesized compound confirmed that they were the same compound. The generation of the impurity was found to be attributed to acetone and iodine in the O-alkylation system.

Several near-infrared (NIR) fluorescent dyes based on aminocyanine have been designed, synthesized, and used for preparation of NIR fluorescent microspheres. Their spectral properties and pH-dependent optical characteristics were investigated. It was found that different substitution at the central position of the dyes led to diverse optical properties, with especially large effects on their spectroscopic properties. Spectroscopic responses of the fluorescent dyes to changes of pH were different. Under acidic conditions, the wavelengths of maximum absorption of the N-substituted cyanine dyes were clearly red shifted. Dyes with an N-substituted piperazidine ring were the most sensitive. The fluorescent microspheres retained the properties of the parent dyes, making them suitable for applications in biological studies.

A hemicyanine dye with imidazole as the acceptor was designed and prepared as a chemosensor for fluoride anions. The experimental results demonstrated that it is a fluorometric probe for fluoride anion with good sensitivity and high selectivity. This probe showed obvious changes in UV–Vis absorption and fluorescence spectra in the presence of fluoride anions, which are attributed to the deprotonation of N–H on the imidazole moiety with fluoride anions.

An impurity was isolated from crude synthesized roflumilast and characterized by 1H NMR, 13C NMR, and HR-MS, which confirmed the structure as N-(3,5-dichloropyrid-4-yl)-4-difluoromethoxy-3-hydroxybenzamide. To further verify the structure, this compound was synthesized from 4-difluoromethoxy-3-hydroxybenzaldehyde. Comparison of the 1H NMR, 13C NMR, HR-MS, and the HPLC spectrum of the impurity and the authentic sample indicated that this impurity was N-(3,5-dichloropyrid-4-yl)-4-difluoromethoxy-3-hydroxybenzamide. This demonstrated the significance of monitoring the reaction process of roflumilast.

A convenient synthetic method has been developed for the synthesis of roflumilast from 4-difluoromethoxy-3-hydroxybenzaldehyde and bromomethyl cyclopropane via O-alkylation, oxidation and N-acylation. With sodium hydroxide as alkali in the last step, the total yield of roflumilast can be up to 68.3 % and the purity of the target product reached 99.2 %. It was obvious that sodium hydroxide showed more economic advantage for scale-up production than sodium hydride or potassium tert-butoxide.

A series of transition metal-based catalysts, other than Pd or Pt-based catalysts, were investigated for catalytic amination of 2,6-dimethylphenol to 2,6-dimethylaniline in a fixed-bed reactor. Ni–Cu–Cr/γ-Al2O3 yielded satisfactory results with 82.08 % conversion and 47.24 % selectivity. The catalysts were characterized by H2-TPR and TEM, and the results obtained showed that the doped Cu and Cr could promote reduction of Ni/γ–Al2O3 and dispersion of the Ni. Reaction conditions, including reaction temperature, flow rate of hydrogen, and ammonia, were studied.

A modified procedure for synthesis of the side chain of ceftazidime-activated thioester has been established. This key intermediate of ceftazidime was obtained by a more eco-friendly process than conventional methods, and the yield was much higher (up to 92.4 %). It was found that different organic bases (triethylamine or pyridine) used in this reaction had different effects. The reaction conditions were also optimized to make the route more competitive and suitable for large-scale industrial production.

Several commercially available supports were examined for cyclization of monoethanolamine to aziridine, and SiO2 was found to yield the best results. The obtained results indicated that selectivity of aziridine was mainly influenced by support. The catalysts were characterized by NH3-TPD and XRD. It was found that SiO2 with lower acidity could inhibit the intermolecular condensations, and thus favored the formation of aziridine. The Cs4P2O7 phase was confirmed as the active site in the supported cesium phosphate catalyst. The reaction parameters were also optimized and a yield of 52% aziridine was obtained over 200 h. Thus, a continuous process for the cyclization of monoethanolamine to aziridine has been established.

A series of chiral pyrrolidine quaternary derivatives were designed and synthesized. It was found that these derivatives are highly efficient organocatalysts for the asymmetric Michael addition reactions of aldehydes and ketones to nitroolefins with high yields (up to 96%), high enantioselectivities (up to 99% ee), and high diastereoselectivities (up to 97:3 dr). Furthermore, catalyst 7a could be recycled without remarkable loss of catalytic activity and stereoselectivity.

A continuous process for reduction of aromatic ketones to the corresponding aromatic alkanes over Cu30Cr10/γ-Al2O3 was established in a fixed-bed reactor. A series of aromatic ketones were examined, and all of the corresponding aromatic hydrocarbons were obtained in more than 95% yield. The catalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and H2-temperature programmed reduction. Cu0 is believed to be the active center of the catalyst. Cr was found to have an important effect on catalytic activity and stability.

A novel co-production process for piperazine and its N-monoalkyl derivatives has been established. N-β-hydroxyethyl-1,2-ethylenediamine and alcohols were used as the starting materials and the process was carried out over Cu–Cr–La/γ-Al2O3 in a fixed-bed reactor. Alcohols acted not only as the solvent but also as the alkylating reagent. The catalyst was characterized by XRD, XPS and BET. The results obtained showed that Cu0 particles in the catalyst were the active sites and doping with La led to enhancement of catalyst activity. Process conditions including reaction temperature, hydrogen pressure, and molar ratio of the reagents were optimized and the distribution of the products was found to be markedly dependent on reaction temperature. Using optimum conditions, piperazine and its N-monoalkyl derivatives were obtained with satisfactory yields and distributions. The catalyst performed well for over 300 h.