Manganese‐Catalyzed Dehydrogenative [4+2] Annulation of N?H Imines and Alkynes by C?H/N?H Activation

Described herein is a manganese‐catalyzed dehydrogenative [4+2] annulation of N H imines and alkynes, a reaction providing highly atom‐economical access to diverse isoquinolines. This transformation represents the first example of manganese‐catalyzed C H activation of imines; the stoichiometric variant of the cyclomanganation was reported in 1971. The redox neutral reaction produces H₂ as the major byproduct and eliminates the need for any oxidants, external ligands, or additives, thus standing out from known isoquinoline synthesis by transition‐metal‐catalyzed C H activation. Mechanistic studies revealed the five‐membered manganacycle and manganese hydride species as key reaction intermediates in the catalytic cycle.     

A novel strategy to the synthesis of 4-anilinoquinazoline derivatives

A novel approach to prepare 4-anilinoquinazoline derivatives based on the transformation of indoline-2,3-dione to formamidine was developed. The processes with this approach are simple, efficient, and environmentally friendly. The efficiency of this approach was evaluated by synthesizing 17 4-anilinoquinazolines and comparing the obtained yields with those achievable through conventional synthetic methods. It was the first time that compounds 8d, 8e, 8h, and 13b–f were synthesized. The characteristics of the IR and the UV spectra of these compounds and the effects of their substituents on the spectra were observed.     

Facile One-Pot Method for the Synthesis of Polysubstituted Phthalide Derivatives

A new three-component cyclization method is described involving two starting materials, ethyl 4-chloroacetoacetate and aldehydes, catalyzed by piperidine, acid, and iodine. Ten corresponding polysubstituted phthalides are formed with good yields (44–78%). A mechanism of the reaction is also proposed.     

Substituent effects on the redox potentials of dihydroxybenzenes: theoretical and experimental study

The redox reactions of p-hydroquinone and pyrocatechol undergo a two-proton-two-electron process in aqueous solution. We calculated their redox potentials at the B3LYP/6-311+G(d,p) level, and verified the values by employing cyclic voltammetry experiments. Then we selected seven substituent groups (–F, –Cl, –OH, –COOH, –CN, –NH₂, and –NO₂ groups) to systematically investigate the substituent effect, including the sort, position, and number of the substituent, on the redox potentials of p-hydroquinone and pyrocatechol. The calculated results show that –NH₂ and –OH groups can decrease the redox potentials, while –F, –Cl, –COOH, –CN, and –NO₂ groups increase the potential values of p-hydroquinone and pyrocatechol. The calculations can accurately predict the substituent effects on the redox potentials of pyrocatechol and p-hydroquinone. We would expect that the accurate calculation results for the model systems could be applied in the prediction of electrode potentials of other molecules.     

One-pot reaction for the concise synthesis of spiro[benzofuran-2,2′-naphthalen]-1′-one derivatives

A novel one-pot two-step protocol has been developed to synthesize various spiro[benzofuran-2,2′-naphthalen]-1′-one derivatives from the three-component reaction of tetralones, 2-hydroxyphenyl functionalized α,β-unsaturated ketones, and iodine. One C–C bond and one C–O bond have formed during this process. The notable features of this protocol are simple and mild reaction conditions, applicable to a wide range of readily available starting materials, good yields (up to 91%), and excellent stereoselectivities (up to 97:3).     

Isoquinoline skeleton synthesis via chelation-assisted C−H activation

Transition-metal-catalyzed isoquinoline synthesis that profits from the strategy of chelation-assisted C−H activation has flourished over the past decade. By virtue of the directed C−H bond cleavage of imines, amines, amidines, oximes, hydroximoyl halides, hydrazones, or azines, diverse isoquinoline derivatives have been accessed from alkynes, conjugated dienes, or diazo compounds under the catalysis of rhodium, ruthenium, palladium, nickel, or manganese. This digest summarizes the annulation reactions via chelation-assisted C−H activation leading to isoquinolines, isoquinolinium salts, or isoquinoline N-oxides.     

Total synthesis of (−)-Englerin A

A novel and efficient total synthesis of Englerin A is reported. The synthesis featured an intramolecular olefin metathesis ring closure reaction and a highly stereoselective oxygen bridge formation induced by an iodonium ion. This strategy can be used for the synthesis of natural products Englerin A and Englerin B and can provide flexibility in the preparation of various 9-substituted analogues of Englerin A for further structure–activity relationship studies.     

Synthesis and preliminary biological evaluation of 99mTc(CO)3-labeled pegylated 2-nitroimidazoles

This work reports the synthesis, radiolabeling and preliminary biodistribution results in tumor-bearing mice of ^99mTc(CO)₃-labeled pegylated (PEG) 2-nitroimidazoles for tumor hypoxia imaging. The novel 2-nitroimidazole derivatives were successfully synthesized by conjugation of tridendate chelators to 2-nitroimidazole via PEG₃ linker. Radiolabeling was performed in high yield with [^99mTc(CO)₃]⁺ core to get cationic [^99mTc(CO)₃(BPA-PEG₃-NIM)]⁺, neutral [^99mTc(CO)₃(AOPA-PEG₃-NIM)] and anionic [^99mTc(CO)₃(IDA-PEG₃-NIM)]^? respectively, all of which were hydrophilic and stable at room temperature. Biodistribution studies in tumor-bearing mice showed that ^99mTc(CO)₃-labeled pegylated 2-nitroimidazoles accumulated in the tumor with low uptake. ^99mTc-chelate and charge had significant impact on partition coefficient, radiotracer tumor uptake and pharmacokinetic properties. The results indicate the need for synthetic modification of the parent 2-nitroimidazole derivatives and the ^99mTc-chelate with a view to improve the tumor targeting efficacy and in vivo kinetic profiles.     

多手性中心联萘-2-芳甲羟基-2'-醇(Ar-BINMOLs):一类可应用于不对称催化反应的新型手性配体

近年来,我们基于1,1'-联萘基-2,2'-二酚(BINOL)为手性源成功地发展了一类多手性中心化合物联萘-2-芳甲羟基-2'-醇(Ar-BINMOLs),它是BINOL的单苄醚化合物经过不对称[1,2]-Wittig重排合成得到的,涉及C—O键的断裂与新C—C的构建反应,由轴手性诱导产生新的碳手性中心,结构独特新颖,同时具有C2轴手性和sp3碳手性的光学纯醇酚类化合物.目前,Ar-BINMOLs作为新型手性配体应用于不对称催化反应已有不少的报道.基于BINOL衍生物以及近几年Ar-BINMOLs及其衍生物的研究进展,重点阐述了其作为新型手性配体或手性骨架在不对称催化反应中的应用研究进展.     

Simultaneous determination of trifloxystrobin and trifloxystrobin acid residue in rice and soil by a modified quick,easy, cheap,effective, rugged,and safe method using ultra high performance liquid chromatography with tandem mass spectrometry

A sensitive analytical method for the simultaneous determination of trifloxystrobin and its metabolite trifloxystrobin acid in rice including straw, bran, brown rice and soil was developed by using ultra high performance liquid chromatography coupled with tandem mass spectrometry. The fungicide trifloxystrobin and its metabolite trifloxystrobin acid were extracted using acetonitrile with 1% formic acid v/v and subsequently cleaned up by primary secondary amine, octadecylsilane or graphitized carbon black prior to ultra high performance liquid chromatography coupled with tandem mass spectrometry. The determination of two target compounds was achieved in less than 3 min using an electrospray ionization source in positive mode. The limits of detection were below 0.22 μg/kg and the limits of quantification did not exceed 0.74 μg/kg in all matrices, which were much lower than the maximum residue levels established by the Codex Alimentarius Commission. The overall average recoveries in four matrix at three levels (0.1, 1.0 and 5.0 mg/kg) ranged from 74.2 to 107.4% with a relative standard deviations of less than 7.8% (n = 5) for both analytes. The method was demonstrated to be convenient and reliable for the routine monitoring of trifloxystrobin and its metabolite. The developed method was validated and applied for the analysis of degradation study samples.