Publications by authors named "Zhanhui Yang"

In this study, an iridium-catalyzed selective 1,4-reduction of α,β-unsaturated carbonyl compounds is realized, with water as a solvent and formic acid as a hydride donor. The new efficient iridium catalyst features a 2-(4,5-dihydroimidazol-2-yl)quinoline ligand. The chemoselectivity and catalyst efficiency are highly dependent on the electronic and steric properties of the substrates.

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Herein, we report a sustainable and efficient method for the synthesis of structurally diverse phthalimidines from 2-formylbenzoic acid and primary amines using an iridium-catalyzed reductive lactamization strategy. The advantages of this method, such as the use of water-ethanol as a solvent, broad substrate scope, high catalyst efficiency (/ up to 10000), good scalability, and easy purification, enable it to be a practical approach to phthalimidines. It is suggested that iridium hydride formation is involved in the rate-limiting step.

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The PyBox-La(OTf)-catalyzed enantioselective Diels-Alder cycloaddition of 2-alk-2-enoylpyridines with cyclopentadiene is realized, producing enantiopure disubstituted norbornenes, which possess four contiguous stereocenters and are biologically relevant structures in up to 92:8 dr and 99:1 er.

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The chiral aziridine-containing vicinal iminophenol tridentate ligands (named salazins) are a class of readily prepared chiral ligands from enantiopure aziridines and salicylaldehydes. Their scandium and yttrium triflate complexes show excellent reactivity and enantioselectivities in the catalytic asymmetric aldol condensation of electron-deficient aromatic aldehydes and ketones, including acetone and cycloalkanones. The stereoselectivity is rationalized to the strong π-stacking interaction between aromatic aldehydes and the vicinal iminophenol group in the chiral ligands.

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Planar-chiral cyclophanes have gained considerable concerns for drug discovery due to their unique conformational strain and 3D structure. However, the enantioselective synthesis of planar-chiral cyclophanes is a long-standing challenge for the synthetic community. We herein describe an N-heterocyclic carbene (NHC)-catalyzed asymmetric construction of planar-chiral cyclophanes.

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A practical and efficient protocol for synthesis of >99% diastereopure - and -alkenyl nitriles is developed, through tetramethylthiourea-mediated stereospecific deoxygenation of respective - and -cyanoepoxides in ethanol. The desired products are obtained in excellent yields.

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An iridium-catalyzed and phenol-directed deoxygenation of benzylic alcohols comes as an alternative access to 4-alkylphenols, featuring low catalyst loading (/ up to 20,000, TOF up to 12,400 h), high functionality compatibility, and excellent site-selectivity. The applications in late-stage modification of steroids and gram-scale total synthesis of a extract are highlighted. Mechanistically, the intermediacy of quinone methide controls the site-selectivity, and the formation of iridium hydride serves as the rate-limiting step.

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To evaluate the clinical efficacy and the influence of fibrinogen, homocysteine and prognosis in acute ischemic stroke (AIS) treated with tirofiban plus TERVO stent thrombectomy. A retrospective study was conducted among 82 patients with AIS admitted to the Department of Neurology in Hengshui People's Hospital from December 2018 to December 2020 and they were evenly divided into control group and study group according to different methods. The control group received TERVO stent thrombectomy; the study group received tirofiban plus.

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The last piece of the puzzle: Furan-2-yl anions are first demonstrated as robust γ-oxo and γ-hydroxyl acyl anion equivalents to convert aldehydes and ketones into trifunctionalized dihydroxyl ketones and hydroxyl diones through sequential nucleophilic addition, Achmatowicz rearrangement, and herein freshly established iridium-catalyzed highly selective transfer hydrogenation reduction.

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A highly chemoselective conversion of -disubstituted nitroalkenes to ketones is developed. An acid-compatible iridium catalyst serves as the key to the conversion. At a 2500 ratio, nitroalkenes were readily converted to ketones in up to 72% isolated yields.

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An iridium-catalyzed highly stereoselective transfer hydrogenation of N-protected 2,4-disubstituted-1,5-benzodiazepines as well as dibenzo[1,5]oxa/thiazepines is realized in an aqueous solvent under acidic conditions, with formic acid as the hydride donor. Only -products are obtained in all the cases where diastereoselective issues are associated. The catalyst efficiency is highly dependent on the electronic and steric properties of the substrates.

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Correction for 'Catalytic (3 + 2) umpolung annulations of α-thioacyl carbenes with aryl isothiocyanates' by Ziyang Dong , , 2022, , 7980-7983, https://doi.org/10.1039/D2CC02882D.

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1,2,3-Thiadiazoles serve as masked S-electrophilic thia-1,3-dipoles. Under rhodium/racemic BINAP catalysis, they undergo denitrogenative (3 + 2) umpolung transannulations with aryl isothiocyanates with inverse regioselectivity and excellent stereoselectivity, yielding -aryl 3-1,2-dithiol-()-3-imines in a redox-neutral, step-efficient, and functionality-tolerant manner. An intramolecular S-S bond is impressively forged.

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With the adoption of a ring-strain-release strategy, iridium-catalyzed transannulations with norbornene derivatives are achieved in a diastereospecific and enantioselective manner. The first asymmetric transannulations of 1,2,3-thiadiazoles are reported.

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Excellent and unique diastereoselectivity is observed in the iridium-catalyzed deoxygenation of tertiary cyclohexanols and cyclopentanols. The substituent effect on the diastereoselectivity and detailed control models are analyzed case by case, using tertiary monocyclic and polycyclic cyclohexanols, bicyclic bridged cycloalkanols, and cyclopentanols as the model substrates. The selectivity is decided by the steric environment of the carbocation intermediates and is independent of the catalyst loading.

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Objective: This study aimed to investigate the clinical efficacy of Nifedipine tablets plus Aspirin for hypertensive disorder complicating pregnancy and the effect on coagulation function and hemorheology.

Methods: A retrospective analysis of the clinical data from 108 patients with gestational hypertension hospitalized between March 2016 and March 2017 was carried out. These patients were randomly assigned into a research group and a control group, with 54 patients in each group.

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A rhodium-catalyzed denitrogenative formal (3 + 3) transannulation of 1,2,3-thiadiazoles with alk-2-enals is achieved, producing 2,3-dihydrothiopyran-4-ones in moderate to excellent yields. An inverse KIE of 0.49 is obtained, suggesting the reversibility of the oxidative addition of thioacyl Rh(i) carbenes to alk-2-enals.

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Bridged [3.3.1]-bisaminal structures, namely 6,12-epiminodibenzo[,][1,5]diazocines, are herein named McGeachin-type bisaminals.

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The intramolecular C-H insertions of carbenes derived from 2-diazo-2-sulfamoylacetamides were studied. 2-Diazo-2-sulfamoylacetamides were first prepared from chloroacetyl chloride and secondary amines through acylation followed by sequential treatments with sodium sulfite, phosphorus oxychloride, secondary amines, and 4-nitrobenzenesulfonyl azide. The results indicate that: (1) 2-diazo--dimethyl-2-(-diphenylsulfamoyl)acetamide can take the formal aromatic 1,5-C-H insertion in its -phenylsulfonamide moiety to afford the corresponding 1,3-dihydrobenzo[]isothiazole-3-carboxamide 2,2-dioxide derivative; (2) no aliphatic C-H insertions occur for 2-diazo-2-(-dialkylsulfamoyl)acetamides; and (3) for 2-diazo--phenyl-2-(-phenylsulfamoyl)acetamides, the formal aromatic 1,5-C-H insertion in the -phenylacetamide moiety is favorable to afford the corresponding 3-sulfamoylindolin-2-one derivatives as sole or major products.

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Thioethers are converted to thiocyanates via fluorium-initiated dealkylative cyanation. Selectfluor is used as the oxidant, and trimethylsilyl cyanide is used as the cyanation reagent. The well-streamlined procedure is user-friendly, operationally simple, and step-economical.

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A rhodium-catalyzed 1,1-hydroacylation of thioacyl carbenes with alkynyl and alkenyl aldehydes and subsequent 6- endo-trig/dig cyclization are realized, giving structurally diverse 4 H-thiopyran-4-ones and 2,3-dihydro-4 H-thiopyran-4-ones in moderate to good yields. The oxidative addition of Rh(I) to aldehydes is proposed to be the turnover-limiting step. Manipulations of estrones demonstrate the applications of our formal (3 + 3) transannulations in the structural modifications of natural products.

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Primary alcohols are converted into dialkyl disulfides via heating in situ generated O-alkyl S-difluoro(ethoxycarbonyl)methyl xanthates from ethyl bromodifluoroacetate and potassium xanthates, prepared from primary alcohols and carbon disulfide in the presence of KOH. The reaction mechanism is suggested as an alkyl C[1,3] shift followed by a radical mechanism. This extends to the Chugaev elimination which yields olefins.

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Stereochemical models and mechanistic insights are proposed for [2 + 2 + 2] annulations of thioketenes and imines on the basis of experimental and computational investigations. In the [2 + 2 + 2] annulations involving cyclic imines, the zwitterionic intermediates generated from monosubstituted thioketenes and the cyclic imines undergo a stepwise nucleophilic endo-addition/Si-face attack pathway with a second imines molecule, giving initially (2,4)-cis-(4,5)-cis-[2 + 2 + 2] annuladducts, which completely epimerize into the corresponding (2,4)-cis-(4,5)-trans-annuladducts under basic reaction conditions. The annuloselectivity of thio-Staudinger cycloadditions is dependent on the substituents of both thioketenes and imines.

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The [2 + 2] cycloadditions of thioketenes and imines are named as thio-Staudinger cycloadditions. The diastereoselectivity in thio-Staudinger cycloaddtions of alkyl/alkenyl/aryl-substituted thioketenes is rationalized. The steric effects of the thioketenes play an extremely important role in deciding the diastereoselectivity (cis/trans selectivity) through controlling exo- and endo-attack and subsequent ring closure.

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The -nitro effect was discovered in sulfa-Staudinger cycloadditions of ethoxycarbonylsulfene with linear imines. When an -nitro group is present at the -aryl substituents of linear imines, the sulfa-Staudinger cycloadditions deliver -β-sultams in considerable amounts, together with the predominant -β-sultams. In other cases, the above sulfa-Staudinger cycloadditions give rise to -β-sultams exclusively.

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