Cross-dehydrogenative coupling strategy for phosphonation and cyanation of secondary N-alkyl anilines by employing 2,3-dichloro-5,6-dicyanobenzoquinone

The cross-dehydrogenative coupling strategy for metal-free phosphonation and cyanation of secondary N-alkyl anilines has been developed firstly under mild reaction conditions. Based on detailed optimization of reaction conditions, the substrate generality of N-alkyl anilines and various hydrogen phosphonates has been investigated, and a series of versatile α-aminophosphonates and α-aminonitriles were therefore furnished in good to excellent yields. A plausible collective reaction mechanism through dehydrogenation to imine formation, then to respective α-aminophosphonates and α-aminonitriles was proposed.     

Allylation and cyanation of aza-aromatics activated by chloroformate and a catalytic amount of iodine

Allyltrimethylsilane and trimethylsilyl cyanide undergo smooth addition to N-acylated quinolines in the presence of a catalytic amount of iodine to afford 2-allyl- and 2-cyano-1,2-dihydroquinoline derivatives, respectively in good yields with high chemo- and regioselectivity. A variety of functional groups such as alkyl, alkoxy, halo, and nitro functionalities are tolerated under the reaction conditions.     

Direct oxidative C(sp3) -H cyanation of secondary benzylic ethers

A practical and efficient oxidative CH cyanation of secondary benzylic ethers with TMSCN in the presence of DDQ is described for the first time. The metal-free process is well tolerated with a wide variety of electronically varied α-monosubstituted isochromans for the synthesis of isochromans bearing α-aryl α-cyano substituent patterns.     

Structural characterization of a copper(II) complex containing oxidative cyclization of N-2-(4-picolyl)-N′-(4-methoxyphenyl)thiourea,new ligands of 4-picolylthiourea derivatives and the precursor molecular structure of oxidative cyclization of N-(2-pyridyl)-N′-(4-methoxyphenyl)thiourea

Three new compounds of aryl thiourea derivatives, namely N-2-(4-picolyl)-N′-(4-methoxyphenyl)thiourea (L1), N-2-(6-picolyl)-N′-(4-methoxyphenyl)thiourea (L2) and N-2-(4-picolyl)-N′-(4-nitrophenyl)thiourea (L3), and the new copper(II) complex [Cu(4PicTz4OMePh)(OAC)(EtOH)] (C1), as a result of oxidative cyclization of the ligand (L1), were synthesized. In addition, pure precursor (P1), as the product of the oxidative cyclization of N-(2-pyridyl)-N′-(4-methoxyphenyl)thiourea (L4), was isolated and characterized. Ligands (L1) and (L2) were characterized by ¹H and ¹³C NMR and single crystal X-ray analysis. ¹H NMR spectroscopy showed strong hydrogen bonding interactions between N′H-functionalities and the pyridine nitrogen atoms as well as weak intermolecular hydrogen bonding between the thione sulfur and the NH hydrogen. Structural studies of complex (C1) showed that the copper ion is five-coordinated with a square-pyramidal environment. The oxidative cyclization of ligand (L1) results in an anionic bidentate ligand in complex (C1). Both ligand (L1) and precursor (P1) crystallize as centrosymmetric dimers.     

A robust palladium-catalyzed cyanation procedure: beneficial effect of zinc acetate

Conditions that ensure a more reproducible Pd(0)-mediated procedure to convert aryl bromides to aryl cyanides have been developed that entail the use of zinc dust to keep the Pd in the zero oxidation state and zinc acetate to ensure high catalytic activity. This procedure is applicable to a wide range of substrates and obviates the need for stringent removal of oxygen from the reaction medium.     

TEMPO-catalyzed oxidative dimerization and cyanation of indoles for the synthesis of 2-(1H-indol-3-yl)-3-oxoindoline-2-carbonitriles

A method for the combinative oxidative homo dimerization and cyanation of free indole derivatives catalysed by TEMPO along with silver carbonate was demonstrated for the first time This new methodology is both atom and step efficient and is applicable to a broad scope of substrates, allowing the synthesis of a range of synthetically valuable 2-(1H-indol-3-yl)-3-oxoindoline- 2-carbonitriles in moderate to excellent yields. Furthermore, selected compounds 6b and 6g exhibit moderate to good anti-schistosomicidal activities.     

I2/Li2CO3-promoted cyanation of diarylalcohols through a dual activation process

One-step base promoted strategy for cyanation of α,α-diaryl alcohols has been developed under mild and transition metal-free conditions. This method provides a straightforward and facile way towards the synthesis of β,γ-unsaturated nitriles and α-phenylnitiriles from α-vinyl carbinols and α,α-diaryl methanols, respectively, up to 99% yield. Moreover, various azides and ethers could also be accessed from their respective nucleophiles under standard reaction conditions.     

Shape-dependent catalytic activity of copper oxide-supported Pd(0) nanoparticles for Suzuki and cyanation reactions

Palladium nanoparticles supported on different shapes of nanocrystalline CuO are prepared by the treatment of Cu(NO₃)₂ and Pd(OAc)₂ in polyethylene glycol (PEG-6000). The shapes of the CuO/Pd composite are dependent on the amount of PEG used. Suzuki coupling was catalyzed efficiently by the oval-shaped material, whereas the rod shape facilitates the cyanation reaction. The CuO/Pd catalyst is recovered and reused for subsequent Suzuki reactions; however, cyanation poisons the catalyst for further use. Both these reactions are very clean and high yielding.     

N,N-Ethylene-bridged flavinium salts derived from l-valinol: synthesis and catalytic activity in H2O2 oxidations

Three chiral N¹,N¹⁰-ethylene-bridged flavinium salts with a stereogenic centre derived from l-valinol are prepared and investigated as oxidation catalysts. These salts efficiently catalyse chemoselective H₂O₂ oxidation of sulfides to sulfoxides and the oxidation of 3-phenylcyclobutanone to the corresponding lactone at room temperature. The flavinium salts react with hydrogen peroxide to form flavin-10a-hydroperoxide, which is the agent responsible for oxidation of the substrate.     

Optimisation and scale-up of microwave assisted cyanation

A microwave enhanced palladium catalysed cyanation procedure was optimised for the final step of a production method for citalopram 2. The method was demonstrated on multigram batch scale for the synthesis of escitalopram (S)-2 and then in a stop-flow continuous process for citalopram.     

An efficient palladium catalytic system for microwave assisted cyanation of aryl halides

Application of a new catalytic system for cyanation reaction of various aryl halides using K₄[Fe(CN)₆] as cyanating source was examined. The reactions were performed under microwave irradiation and results showed that application of this catalytic system and DMF at 130 °C minimized the reaction times from hours to minutes in good to excellent yields.     

Organocatalytic desymmetrization of cyclic meso-anhydrides through enantioselective alcoholysis with functionalized primary nitroallylic alcohols

The direct organocatalytic desymmetrization of cyclic meso-anhydrides was achieved by alcoholysis with nitroallylic alcohols. The reaction between primary nitroallylic alcohols and cyclic meso-anhydrides catalyzed by cinchonidine derived thiourea organocatalyst II (10 mol %) proceeded smoothly. The corresponding hemiesters were obtained in high chemical yields with high to excellent levels of stereoselectivity (up to 90% yield and 99% ee). On the other hand, the reversal of enantioselectivity was observed when an amino cinchonidine derivative (III) was used as the organocatalyst under the similar reaction conditions. This demonstrated an example of activation of the nucelophilic component in the desymmetrization of cyclic meso-anhydrides.     

3-Quinuclidinol as a nucleophilic catalyst for the cyanation of 2-chloropyrimidines

3-Quinuclidinol serves as an effective nucleophilic catalyst for the preparation of 2-cyanopyrimidines by cyanation of 2-chloropyrimidines with potassium cyanide in good yields.     

Palladium-catalyzed domino Heck/cyanation: synthesis of 3-cyanomethyloxindoles and their conversion to spirooxoindoles

3′-Alkyl-3-cyanomethyloxindoles, prepared by a palladium-catalyzed domino Heck/cyanation, were efficiently converted to spiropyrrolidinyl-, spiropiperidinyl- and spirocyclopropyl-oxindoles. The so-obtained spirooxindoles bearing three diversity points were further functionalized via selective N-acylation, N-alkylation, N-sulfonylation, S_NAr reaction and Buchwald-Hartwig N-arylation reaction to reach diverse set of heterocycles.     

Copper-catalyzed cyanation of aryl iodide with the combined cyanide source of urea and DMSO

A simple copper-catalyzed cyanation of aryl iodide with the combination of urea and dimethyl sulfoxide as a cyanide source is achieved, providing nitriles in moderate to good yields. This new approach represents an exceedingly practical and safe method for the synthesis of aryl nitriles.     

硫脲氧化反应动力学研究进展

本文综述了硫脲氧化反应动力学的研究进展,根据氧化剂和氧化方式不同,将硫脲氧化体系分成含卤氧化体系和非卤氧化体系两大类,其中含卤氧化体系包括亚氯酸、碘酸、溴酸、卤素单质氧化硫脲的反应体系;非卤氧化体系包括双氧水、自由基、电化学和金属酸盐氧化硫脲的反应体系。总结了不同反应体系的动力学现象和反应机理研究状况,文中还介绍了在硫脲氧化反应动力学研究中光电磁及色谱方法的发展状况,提出硫脲氧化反应动力学机理研究突破可能途径。     

One-pot synthesis of N-allylthioureas using supported reagents

A simple and efficient method has been developed for the synthesis of N-allylthioureas from allylic bromides in one-pot by using a supported reagents system, KSCN/SiO₂-RNH₃OAc/Al₂O₃, in which allyl bromide reacts first with KSCN/SiO₂ and the product, allyl isothiocyanate, reacts with RNH₃OAc/Al₂O₃ to give the final product, N-allylthiourea, in good yield.     

Novel synthesis of aminoacetonitriles via the selective demethylation of quaternary ammonium salts

N-Methyl cyclic amines readily formed quaternary ammonium salts upon treatment with iodoacetonitrile in high yields (70–96%). The latter were selectively demethylated by heating in dimethylformamide to give aminoacetonitriles in moderate to good overall yields (36–69%).     

Pd-catalyzed cyanation of benzyl chlorides with nontoxic K4[Fe(CN)6]

Non-toxic K₄[Fe(CN)₆] was demonstrated to be effective as a green cyanating agent for the cyanation of alkyl halides using PPh₃/Pd(OAc)₂ as a catalyst system. The presented method allowed a series of benzyl chlorides to be smoothly cyanated in up to 88% yield. In order to avoid or suppress the deactivation of the catalyst, the reaction was required to be performed in a stringent inert ambiance.