A highly efficient asymmetric hydrogenation of azepine/oxazepine-type seven-member cyclic imine hydrochlorides was successfully developed using Rh/bisphosphine-thiourea ligand ZhaoPhos, affording various chiral seven-member cyclic amines with full conversions, high yields, and excellent enantioselectivities (up to 96% yield, >99% ee). Additionally, this asymmetric hydrogenation can proceed well on gram scale with excellent ee value. Moreover, control experimental results displayed that the anion-bonding interaction between the chloride ion of the substrate and thiourea motif of the ZhaoPhos played an important role to obtain excellent enantioselectivity.

ABSTRACTA series of 2-(arylimino)benzylidene-9-arylimino-5,6,7,8-tetrahydrocyclohepta[b]pyridyliron(II) chlorides was synthesized and characterized using FT-IR and elemental analysis, and the molecular structures of complexes Fe3 and Fe4 have been confirmed by the single-crystal X-ray diffraction as a pseudo-square-pyramidal or distorted trigonal-bipyramidal geometry around the iron core. On activation with methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all iron precatalysts exhibited high activities toward ethylene polymerization with a marvelous thermo-stability and long lifetime. The Fe4/MAO system showed highest activity of 1.56 × 107 gPE·mol−1(Fe)·h−1 at 70 °C, which is one of the highest activities toward ethylene polymerization by iron precatalysts. Even up to 80 °C, Fe3/MAO system still persist high activity as 6.87 × 106 g(PE)·mol−1(Fe)·h−1, demonstrating remarkable thermal stability for industrial polymerizations (80–100 °C). This was mainly attributing to the phenyl modification of the framework of the iron precatalysts. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 830–842

(NHC)-Cu-catalyzed C(sp)–C(sp3) bond formation has been successfully achieved under mild conditions. Nonactivated alkyl triflates, which could be easily derived from alcohols, were utilized as C–O electrophiles. Mechanistic studies suggested that copper acetylide was the active species. Scale-up reactions further demonstrated the practicality and efficiency of the developed strategy.

A new family of strained imino-cyclopenta[b]pyridines, 7-(ArN)-6-Me2C8H5N (Ar = 2,6-Me2Ph (L1), 2,6-Et2Ph (L2), 2,4,6-Me3Ph (L3), 2,6-Et2-4-MePh (L4), 2,6-i-Pr2Ph (L5)), have been synthesized in reasonable yield by a sequence of reactions from 2-chloro-cyclopenta[b]pyridin-7-one. Treatment of L1 and L3 with NiCl2·6H2O generates mononuclear bis-ligated [7-(ArN)-6-Me2C8H5N]2NiCl2 (Ar = 2,6-Me2Ph (Ni1), 2,4,6-Me3Ph (Ni3)), while with L2 and L4, the chloride-bridged binuclear complexes [7-(ArN)-6-Me2C8H5N]2Ni2(μ-Cl)2Cl2 (Ar = 2,6-Et2Ph (Ni2), 2,6-Et2-4-MePh (Ni4)), have been isolated; no apparent reaction occurred with L5. On activation with either MAO or MMAO, Ni1–Ni4 exhibited high activities towards ethylene polymerization with Ni3 the most active (5.02 × 106 g PE per mol Ni per h at 20 °C); rapid regeneration of the active species (3096–5478 h−1 at 20 °C) is a feature of their catalytic performance. A detailed microstructural analysis of the polyethylenes reveals the presence of vinyl and higher levels of internal vinylene groups indicative of high rates of chain isomerization, e.g., the ratio of (–CHCH–) to (H2CCH–) groups is 2.2 : 1 using Ni3/MAO at 60 °C. Agostic interactions involving γ-, δ- and higher-hydrogens are inferred in addition to β-hydrogen elimination to account for the vinylene groups and the longer chain alkyl branches. The molecular structures of Ni1 and Ni2·2MeOH are also reported.

•2-Chloro/phenyl-7-arylimino-6,6-dimethylcyclopenta[b]pyridine-nickel chlorides•Bulky substituents at the imine group prevent the formation of its nickel complex.•Activated with alkylaluminum reagents, all nickel precatalysts highly oligomerize ethylene.•The substituents within the ligand framework determine oligomer distribution.•DFT calculations reveal that substituents enlongate the Ni-C length in the alkyl intermediates.2-Chloro/phenyl-7-arylimino-6,6-dimethylcyclopenta[b]pyridylnickel chlorides (Ni1–Ni8) were synthesized from the respective ligands L1–L8 and characterized. Upon activation with either methylaluminoxane (MAO) or ethylaluminium sesquichloride (EASC), they show high catalytic activity of up to 10.84 × 106 g(oligomer) mol− 1(Ni) h− 1 in ethylene oligomerization. The products range from butenes to dodecenes for Ni1–Ni4, but are limited to butenes and hexenes in the case of Ni5–Ni8. DFT calculations indicate that the NiC bond length in the model alkyl complexes depends both on the nature of the substituents at the heterocycles and the kind of the alkyl group, shedding some light on the preferences of the precatalysts toward oligomers or polyethylene.2-Chloro/phenyl-7-arylimino-6,6-dimethylcyclopenta[b]pyridylnickel precatalysts, activated with either MAO or EASC, showed high activities for ethylene oligomerization, producing oligomers of butenes to dodecenes with R as Cl and butenes (C4) to hexenes (C6) with R as Ph.Download high-res image (158KB)Download full-size image

•An efficient and recyclable catalytic system for the aerobic alcohol oxidation was developed.•A variety of aldehydes were synthesized from primary alcohols in neat water under room temperature.•A novel PEG-functionalized pyridine triazole was designed and synthesized.A water-soluble PEG-PyTa ligand, conveniently derived from commercially available reagents via a simple synthetic approach, could efficiently promote copper/2, 2, 6, 6-tetramethyl piperidine-1-oxyl (TEMPO)-catalyzed aerobic oxidation of primary alcohols to aldehydes in water under room temperature. A number of primary benzylic, allylic alcohols and heteroaryl methanols were selectively converted into their corresponding aldehydes with excellent yields. The oxidation products could be isolated by simple extraction, and the residual aqueous phase containing the catalyst Cu(OTf)2/PEG-PyTa could be reused at least 7 times.

The asymmetric hydrogenation of β-amino nitroolefins has been successfully achieved by rhodium/bis(phosphine)-thiourea L1 with excellent enantioselectivities and yields (up to 96% ee, 96% yield, >99% conversion, TON up to 1000) under mild conditions. Chiral β-amino nitroalkane products and their derivatives are versatile intermediates in organic synthesis.

A new biomimetic catalytic oxidation system which employs 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as the catalyst, molecular oxygen as the terminal oxidant and iron(II) phthalocyanine (FeIIPc) as the electron-transfer mediator has been developed. This system can be applied for oxidative deprotection of PMB ethers, alcohol oxidation, aromatization and α,β-unsaturated aldehyde formation. After immobilizing FeIIPc on multi-walled carbon nanotubes, it can be reused without loss of activity.

A facile and efficient transformation of arylboronic acids to their corresponding aryl thiocyanates has been successfully developed. Based on the CuCl-catalyzed oxidative cross-coupling reaction between arylboronic acids and trimethylsilylisothiocyanate (TMSNCS) under oxygen atmosphere, the transformation can be readily conducted at ambient temperature. The newly-developed protocol provided a competitive synthetic approach to aryl thiocyanates that can tolerate a broad range of reactive functional groups and/or strong electron-withdrawing groups.

A novel copper-catalyzed oxidative alkenylation of thioethers via Csp3–H functionalization to construct allylic thioethers is first demonstrated. Different 1,1-disubstituted olefins could cross-couple with thioethers to generate the corresponding alkenylation products in moderate to excellent yields. This reaction is supposed to proceed via a radical process.

A facile and efficient protocol for direct transformation of p-methoxybenzyl (PMB) ethers to aldehydes or ketones via a catalytic aerobic oxidation process has been developed. The reaction was performed with the combination of catalytic amounts of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), 2,2,6,6-tetramethylpiperidine N-oxy (TEMPO), and tert-butyl nitrite (TBN), with molecular oxygen as terminal oxidant. A variety of PMB ether substrates derived from benzylic alcohols, heteroaromatic alcohols, and aliphatic alcohols, were converted to their corresponding carbonyl compounds in good conversions and selectivities.A facile and efficient protocol for direct transformation of p-methoxybenzyl (PMB) ethers to aldehydes or ketones via a catalytic aerobic oxidation process has been developed. The reaction was performed with the combination of catalytic amounts of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), 2,2,6,6-tetramethylpiperidine N-oxy (TEMPO), and tert-butyl nitrite (TBN), with molecular oxygen as terminal oxidant. A variety of PMB ether substrates derived from benzylic alcohols, heteroaromatic alcohols, and aliphatic alcohols, were converted to their corresponding carbonyl compounds in good conversions and selectivities.

An efficient and environmentally benign heterogeneous catalytic process for the synthesis of 2,3-unsubstituted benzo[b]furans has been established via the intramolecular cyclization of 2-aryloxyacetaldehyde acetals. By utilizing tin-exchanged H-β zeolite (Sn-β) as catalyst, a wide range of functionalized 2,3-unsubstituted benzo[b]furans could be prepared in good to excellent yields. The Sn-β zeolite catalyst also exhibited excellent shape selectivity on the cyclization of meta-substituted 2-aryloxyacetaldehyde acetals, and 6-substituted isomers were preferably formed up to 97% regio-selectivity. Moreover, Sn-β zeolite could be easily recovered and reused without any noticeable activity loss.

Phenylsulfonic acid-functionalized SBA-15 silica was found to be an efficient heterogeneous acid catalyst in Bischler cyclization for the synthesis of indole-2-carboxylic esters. Under the optimized conditions, a wide range of substituted 4-nitrobenzyl 3-hydroxy-2-(N-methyl-N-arylamino)-2-enoates could be smoothly transformed to the corresponding 4-nitrobenzyl indole-2-carboxylates in excellent yields (87–99 %). Moreover, the catalyst could be conveniently recovered and reused at least four times without significant loss of catalytic activity.

A facile and efficient protocol for the oxidative deprotection of benzyl-type ethers has been developed. The reaction was performed with catalytic amounts of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and tert-butyl nitrite (TBN) under atmospheric pressure of O2. Under the optimal reaction conditions, a variety of p-methoxybenzyl (PMB), p-phenylbenzyl (PPB), and benzyl (Bn) ethers can be deprotected to their corresponding alcohols in excellent conversions and selectivities.A facile and efficient protocol for the oxidative deprotection of benzyl-type ethers has been developed. The reaction was performed with catalytic amounts of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and tert-butyl nitrite (TBN) under atmospheric pressure of O2. Under the optimal reaction conditions, a variety of PMB, PPB, and Bn ethers can be deprotected to their corresponding alcohols in excellent conversions and selectivities.

A series of N-(2-alkyl-5,6,7-trihydroquinolin-8-ylidene)arylaminonickel(II) dichloride complexes were synthesized in a one-pot reaction with nickel dichloride. All nickel complexes were characterized by elemental and spectroscopic analysis. The molecular structures of representative nickel complexes, as determined by the single crystal X-ray diffraction, are reported. All nickel complexes, when treated with ethylaluminium sesquichloride (Et3Al2Cl3), showed high activities (up to 1.1 × 106 g mol−1 h−1) for ethylene oligomerization, with good thermal stability at 80 °C at 10 atm ethylene. The influence of the reaction parameters on the catalytic behavior was investigated for these nickel-based systems, including variation of Al/Ni molar ratio and reaction temperature.Graphical abstractA series of N-(2-alkyl-5,6,7-trihydroquinolin-8-ylidene)arylaminonickel(II) dichloride complexes, when treated with ethylaluminium sesquichloride (Et3Al2Cl3), showed high activities for ethylene oligomerization, with good thermal stability at 80 °C at 10 atm ethylene.Highlights► N-(2-Alkyl-5,6,7-trihydroquinolin-8-ylidene)arylaminonickel(II) dichloride complexes. ► The molecular structures of representative nickel complexes were determined. ► Activated with Et3Al2Cl3, all nickel pre-catalysts showed high activities for ethylene oligomerization. ► The nickel catalytic systems have good thermal stability at 80 °C under 10 atm ethylene.

The chemoselectivity in the amination of 4-chloroquinazolines with 3-amino-1H-pyrazoles was studied. Under the conditions of Pd2(dba)3/Xantphos/Na2CO3, 4-chloroquinazolines underwent selective amination with the cyclic secondary amino group of 3-amino-1H-pyrazoles, whereas 4-chloroquinazolines were exclusively aminated with the primary amino group of 3-amino-1H-pyrazoles via SNAr substitution in the presence of HCl.

An efficient and improved process for the preparation of diphenylmethyl 7β-phenylacetamido-3-hydroxymethyl-3-cephem-4-carboxylate was developed. With the commercially available 7-aminocephalosporanic acid (7-ACA) as starting material, up to 73.5% overall isolated yield of the titled compound was synthesized in two steps via direct phenylacetylation with phenylacetyl chloride, followed by basic hydrolysis and esterification with diphenyldiazomethane. The newly developed process obviated the use of protecting groups, reduced the environmental footprint, and could be easily controlled and conveniently scaled up for this pivotal intermediate in cephalosporin chemistry.

A series of new chiral pyridine–phosphite ligands have been prepared from (R)-pyridyl alcohols and BINOL-derived chlorophosphite, and successfully employed in the copper-catalyzed enantioselective conjugate addition of diethylzinc to acyclic enones. Using the simple and inexpensive CuBr2 as a precursor, the enantioselective additions to various substituted acyclic enones afforded products in high yields and good enantioselectivities (up to 92% ee).(R)-7-O-((S)-2,2′-O,O-(1,1′-Binaphthyl)-dioxo-phosphite)-2-phenyl-6,7-dihydro-5H-cyclopenta[b]pyridineC34H25NO3PDe >99%[α]D20=+78.1 (c 0.19, CHCl3)Source of chirality: asymmetric reductionAbsolute configuration: (Rc,Sa)(R)-7-O-((R)-2,2′-O,O-(1,1′-Binaphthyl)-dioxo-phosphite)-2-phenyl-6,7-dihydro-5H-cyclopenta[b]pyridineC34H25NO3PDe >99%[α]D20=-221.5 (c 0.42, CHCl3)Source of chirality: asymmetric reductionAbsolute configuration: (Rc,Ra)(R)-7-O-((S)-2,2′-O,O-(1,1′-Binaphthyl)-dioxo-phosphite)-2-chloro-6,7-dihydro-5H-cyclopenta[b]pyridineC28H20ClNO3PDe >99%[α]D20=+231.0 (c 0.16, CHCl3)Source of chirality: asymmetric reductionAbsolute configuration: (Rc,Sa)(R)-7-O-((R)-2,2′-O,O-(1,1′-Binaphthyl)-dioxo-phosphite)-2-chloro-6,7-dihydro-5H-cyclopenta[b]pyridineC28H20ClNO3PDe >99%[α]D20=-206.1 (c 0.16, CHCl3)Source of chirality: asymmetric reductionAbsolute configuration: (Rc,Ra)(R)-8-O-((S)-2,2′-O,O-(1,1′-Binaphthyl)-dioxo-phosphite)-2-phenyl-5,6,7,8-tetrahydroquinoineC35H27NO3PDe >99%[α]D20=+72.9 (c 0.20, CHCl3)Source of chirality: asymmetric reductionAbsolute configuration: (Rc,Sa)(R)-8-O-((R)-2,2′-O,O-(1,1′-Binaphthyl)-dioxo-phosphite)-2-phenyl-5,6,7,8-tetrahydroquinoineC35H27NO3PDe >99%[α]D20=-290.7 (c 0.35, CHCl3)Source of chirality: asymmetric reductionAbsolute configuration: (Rc,Ra)(R)-2-Chloro-6,7-dihydro-5H-cyclopenta[b]pyridin-7-olC8H8ClNOEe >99%[α]D20=-4.1 (c 0.39, CHCl3)Source of chirality: asymmetric reductionAbsolute configuration: (R)

We successfully extended our Rh/bisphosphine-thiourea (ZhaoPhos) catalytic system to asymmetric hydrogenation of α,β-unsaturated N-acylpyrazoles affording products with high yields and excellent enantioselectivities (up to 97% yield, 99% ee). The pyrazole moiety played an important role in providing H-bond acceptor sites, which is critical for achieving high reactivities and enantioselectivities.

(NHC)-Cu-catalyzed C(sp)–C(sp3) bond formation has been successfully achieved under mild conditions. Nonactivated alkyl triflates, which could be easily derived from alcohols, were utilized as C–O electrophiles. Mechanistic studies suggested that copper acetylide was the active species. Scale-up reactions further demonstrated the practicality and efficiency of the developed strategy.

A novel copper-catalyzed oxidative alkenylation of thioethers via Csp3–H functionalization to construct allylic thioethers is first demonstrated. Different 1,1-disubstituted olefins could cross-couple with thioethers to generate the corresponding alkenylation products in moderate to excellent yields. This reaction is supposed to proceed via a radical process.

A facile and efficient transformation of arylboronic acids to their corresponding aryl thiocyanates has been successfully developed. Based on the CuCl-catalyzed oxidative cross-coupling reaction between arylboronic acids and trimethylsilylisothiocyanate (TMSNCS) under oxygen atmosphere, the transformation can be readily conducted at ambient temperature. The newly-developed protocol provided a competitive synthetic approach to aryl thiocyanates that can tolerate a broad range of reactive functional groups and/or strong electron-withdrawing groups.