Sm/TiCl_4 (cat.) system-mediated intermolecular and intramolecular reductive coupling reactions of ketones with esters

Sm/TiCl4 system could well integrate the high reactivity of samarium（Ⅱ） and high deoxygenation capacity of low valent titanium within one system. In this paper, the intermolecular and intramolecular reductive coupling reactions of ketones with esters mediated by metallic samarium （Sm） and a catalytic amount of titanium tetrachloride （TiCl4） were successfully developed. A series of substituted ketones and cyclic β-keto-esters were prepared in moderate to good yields under reflux and neutral conditions.

Catalytic HgCl_2-Samarium System Induced Reductive Coupling of Nitriles with Nitro Compounds

The intermolecular coupling of a nitro group with a cyano group mediated by a Sm(Hg) amalgam prepared from metal samarium powder and catalytic mercury dichloride was studied.

LOW-VALENT TITANIUM INDUCED REDUCTIVE COUPLING OF AROMATIC NTTRILES TO 1,2-ARYLETHANONES

Reductive coupling of aromatic nitriles 1 by titanium tetrachloride/zinc provides an efficient general synthesis of 1,2-arylethanones.

Low-valent Titanium Induced Reductive Coupling Reaction of Aryl Sulfonyl Chlorides with α,β-Unsaturated Esters

The reductive coupling reactions of aryl sulfonyl chloride induced by (TiCl4-Zn) reagent affords diaryl disulfide. However, reaction of aryl sulfonyl chloride with α,β-unsaturated ester under the same condition affords β-arylsulfo ester.

Electromagnetic coupling reduction in dual-band microstrip antenna array using ultra-compact single-negative electric metamaterials for MIMO application

In this paper, an ultra-compact single negative（SNG） electric waveguided metamaterial（WG-MTM） is first investigated and used to reduce the mutual coupling in E ＆ H planes of a dual-band microstrip antenna array. The proposed SNG electric WG-MTM unit cell is designed by etching two different symmetrical spiral lines on the ground, and has two stopbands operating at 1.86 GHz and 2.40 GHz. The circuit size is very compact, which is only λ_0/33.6 ×λ_0/15.1（where λ_0 is the wavelength at 1.86 GHz in free space）. Taking advantage of the dual-stopband property of the proposed SNG electric WG-MTM, a dual-band microstrip antenna array operating at 1.86 GHz and 2.40 GHz with very low mutual coupling is designed by embedding a cross shaped array of the proposed SNG electric WG-MTM. The measured and simulated results of the designed dual-band antenna array are in good agreement with each other, indicating that the mutual coupling of the fabricated dual-band antenna array realizes 9.8/11.1 d B reductions in the H plane, 8.5/7.9 d B reductions in the E plane at1.86 GHz and 2.40 GHz, respectively. Besides, the distance of the antenna elements in the array is only 0.35 λ_0（where λ_0 is the wavelength at 1.86 GHz in free space）. The proposed strategy is used for the first time to reduce the mutual coupling in E ＆ H planes of the dual-band microstrip antenna array by using ultra-compact SNG electric WG-MTM.

Composite metamaterial enabled excellent performance of microstrip antenna array

This paper reports that the split ring resonators and complementary split ring resonators are compounded to construct a novel compact composite metamaterial. The composite metamaterial exhibits a unique property of blocking electromagnetic wave propagating in two directions near the resonant frequency. An example of two-element microstrip antenna array demonstrates that the developed metamaterial enables array performance that is an improvement in comparison with the traditional one, including mutual coupling suppression of 9.07 dB, remarkable side lobe suppression and gain improvement of 2.14 dB. The mechanism of performance enhancement is analysed based on the electric field and Poynting vector distributions in array. The present work not only is a meaningful exploration of new type composite metamaterial design, but also opens up possibilities for extensive metamaterial applications to antenna engineer.

Diastereoselective and Enantioselective Nickel-Catalyzed Reductive Coupling of Imines and Unactivated Alkenes

Herein we report a method for highly diastereoselective and enantioselective nickel-catalyzed reductive coupling of imines and unactivated alkenes.A monodentate chiral spiro phosphoramidite ligand is the key to controlling the enantioselectivity.This efficient,straightforward method allows for the construction of chiral benzocyclic and indole-fused cyclic amines with two contiguous stereogenic centers in good yields from readily accessible starting materials.

Nickel-catalyzed reductive coupling reaction of monofluoroalkyl triflates with alkyl carboxylic acids toward the synthesis of α-alkyl-α-fluoro-alkylketones

The synthesis methods ofα-fluoro-arylketones were well-established through electrophilic/nucleophilic fluorination and transition metal catalyzed cross-coupling.However,due to the site selectivity and substrate restriction,only a few cases have been developed to affordα-alkyl-α-fluoro-alkylketones.Herein,we report a general and efficient method of preparing diverseα-alkyl-α-fluoro-alkylketones via nickelcatalyzed reductive coupling reaction of monofluoroalkyl triflates with low-cost industrial raw material alkyl carboxylic acids.These transformations demonstrate high efficiency,mild conditions,and excellent functional group compatibility.This strategy provides a general and efficient method for the synthesis ofα-alkyl-α-fluoro-alkylketones。

Nickel-catalyzed cross-electrophile C–Ge coupling of benzyl pivalates and chlorogermanes

The C–Ge cross-coupling offers a promising approach for the precise synthesis of organogermanes. However, the current methods are primarily effective in the germylation of organo(pseudo)halides. This work demonstrates the possibility of transferring low-cost and easily available ester groups into organogermanes through the cleavage of stable C–O bonds. Primary,secondary, and even tertiary benzylic pivalates were coupled well with chlorogermanes. The reactions proceed under mild conditions. The scalability of this reaction and derivatization of the formed benzylgermanes are demonstrated.

Nickel-catalyzed umpolung C-S radical reductive cross coupling of S-(trifluoromethyl)arylsulfonothioates with alkyl halides

A new cooperative nickel reductive catalysis and N,N-dimethylformamide-mediated strategy for umpolung C–S radical reductive cross coupling of S-(trifluoromethyl)arylsulfonothioates with alkyl halides to produce alkyl aryl thioethers is described. This reaction features excellent selectivity, wide functionality tolerance, broad substrate scope, and facile late-stage modification of biologically relevant molecules.Mechanistic studies recognize initial generation of an amidyl radical anion via thermoinduced reduction of DMF with Sn, followed by umpolung reduction and single electron transfer of the nucleophilic sulfonyl moiety to form a sulphydryl radical and engage the Ni^(0)/Ni^(Ⅰ)/Ni^(Ⅲ)/Ni^(I) catalytic cycle.

Bioinspired zinc-mediated umpolung thiolation of alkyl electrophiles: reaction development, scope and mechanism

Zinc-promoted umpolung thiolation of alkyl electrophiles with masked sulfur transfer reagents in the absence of nickel or copper catalysis is described. This protocol proceeds via a SET process of Zn to electrophilic sulfur reagent followed by insertion of Zn into disulfide and nucleophilic thiolation, providing straightforward access to a wide range of alkyl sulfides with broad substrate scope. A neutral TMEDA-ligated four-coordinated zinc thiolate with tetrahedra geometry was synthesized, isolated and fully characterized by NMR, IR and X-ray analysis. More importantly, the chemical reactivity of this active intermediate has been investigated, enabling the construction of C-Se, C-Te, Sb-S and Bi-S bonds to prepare valuable sulfur-containing molecules and beyond.

Mn-mediated reductive C(sp3)–Si coupling of activated secondary alkyl bromides with chlorosilanes

The construction of secondary alkylsilanes is a challenging subject in the synthetic community.The cross-coupling provides a practical solution to address this problem,but it typically relies on organometallic species.Herein,we report an Mn-mediated reductive C(sp^(3))-Si coupling to synthesize these compounds from alkyl and silyl electrophiles.This approach avoids the requirement for activation of Si-Cl by transition metals and thus allows for the coupling of various common chlorosilanes.The reaction proceeds under mild conditions and shows good functional group compatibility.The method offers access toα-silylated organophosphorus and sulfones with a scope that is complementary to those obtained from the established methods.

Boron-promoted reductive deoxygenation coupling reaction of sulfonyl chlorides for the C(sp3)-S bond construction

Herein,we report a borane-promoted reductive deoxygenation coupling reaction to synthesize sulfides.This reaction features excellent functional group compatibility,high efficiency,broad substrate scope,and application in late-stage functionalization of biomolecules.Preliminary mechanistic studies suggest diaryl sulfides are the intermediates of this reaction.Moreover,the real active aryl sulfide anions may be generated in situ with the aid of B2pin2 and react with alkyl tosylates through a concerted SN2 pathway.

Reductive Coupling Cyclization of 1,1-Dicyanoalkenes Promoted by Sm^0/cat. HgCl_2 System

The intermolecular reductive coupling cyclization reactions of 1,1-dicyanoalkenes promoted by Sm-0/cat. HgCl2 were studied. A possible reaction mechanism was proposed.

Nickel-Catalyzed Cross-Electrophile Vinyl–Vinyl Coupling:An Approach to Structurally Versatile Dienylboronates

Cross C–C bond formation of two vinyl electrophiles is a long-standing challenge in synthetic chemistry.Herein,we report a nickel-catalyzed reductive vinyl–vinyl coupling between vinyl triflates and boron-substituted vinyl bromides.This new protocol offers facile access to dienylboronates with high structural complexity and molecular diversity.The reaction proceeds with a broad substrate scope under very mild conditions.The synthetic utility of the method is highlighted by its gram-scale reaction,modification of complex molecules,and diverse transformation of the products.

Simultaneous Fe(Ⅲ) reduction and ammonia oxidation process in Anammox sludge

In recent years, there have been a number of reports on the phenomenon in which ferric iron（Fe（Ⅲ）） is reduced to ferrous iron [Fe（Ⅱ）] in anaerobic environments, accompanied by simultaneous oxidation of ammonia to NO2-, NO3-, or N2.However, studies on the relevant reaction characteristics and mechanisms are rare. Recently, in research on the effect of Fe（Ⅲ） on the activity of Anammox sludge, excess ammonia oxidization has also been found.Hence, in the present study, Fe（Ⅲ） was used to serve as the electron acceptor instead of NO2-,and the feasibility and characteristics of Anammox coupled to Fe（Ⅲ） reduction（termed Feammox） were investigated. After 160 days of cultivation, the conversion rate of ammonia in the reactor was above 80%, accompanied by the production of a large amount of NO3-and a small amount of NO2-. The total nitrogen removal rate was up to 71.8%. Furthermore,quantities of Fe（Ⅱ） were detected in the sludge fluorescence in situ hybridization（FISH） and denaturated gradient gel electrophoresis（DGGE） analyses further revealed that in the sludge, some Anammox bacteria were retained, and some microbes were enriched during the acclimatization process. We thus deduced that in Anammox sludge, Fe（Ⅲ） reduction takes place together with ammonia oxidation to NO2-and NO3-along with the Anammox process.