Functionalization of Liquid‐Exfoliated Two‐Dimensional 2H‐MoS2

Layered two‐dimensional (2D) inorganic transition‐metal dichalchogenides (TMDs) have attracted great interest as a result of their potential application in optoelectronics, catalysis, and medicine. However, methods to functionalize and process such 2D TMDs remain scarce. We have established a facile route towards functionalized layered MoS₂. We found that the reaction of liquid‐exfoliated 2D MoS₂, with M(OAc)₂ salts (M=Ni, Cu, Zn; OAc=acetate) yielded functionalized MoS₂–M(OAc)₂ materials. Importantly, this method furnished the 2H‐polytype of MoS₂ which is a semiconductor. X‐ray photoelectron spectroscopy (XPS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT–IR), and thermogravimetric analysis (TGA) provide strong evidence for the coordination of MoS₂ surface sulfur atoms to the M(OAc)₂ salt. Interestingly, functionalization of 2H‐MoS₂ allows for its dispersion/processing in more conventional laboratory solvents.     

Pd(OAc)2@SBA‐15/PrEn nanoreactor: a highly active,reusable and selective phosphine‐free catalyst for Suzuki–Miyaura cross‐coupling reaction in aqueous media

A series of ordered mesoporous organic–inorganic hybrid material was designed by using the amine‐functionalized SBA‐15 (PdX₂@SBA‐15/N_Y, Y = 1, 2) as solid support for palladium complexes. Among them, the Pd(OAc)₂/ethylenediamine complex encapsulated into SBA‐15 (Pd(OAc)₂@SBA‐15/PrEn or Pd(OAc)₂@SBA‐15/PrNHEtNH₂) exhibits higher activity and selectivity toward Suzuki cross‐coupling reaction under aerobic conditions and water solvent mixture. The SBA‐15/PrEn supported palladium pre‐catalyst could be separated easily from reaction products and used repetitively several times, showing its superiority over homogeneous catalysts for industrial and chemical applications. Copyright © 2013 John Wiley & Sons, Ltd.     

Highly efficient,catalyst‐free,one‐pot,pseudo five‐component synthesis of novel pyrazoline‐containing Schiff bases,metal complexes formation and computational studies via DFT method

In this study, a green and high yielding synthesis of novel pyrazoline‐containing Schiff bases via a one‐pot pseudo five‐component condensation reaction under catalyst‐free conditions in EtOH at room temperature is described. Initially, the reaction of 1,1‐bis(methylthio)‐2‐nitroethylene (BMTNE), with NH₂NH₂.H₂O is used for situ preparation of 1,1‐dihydrazino‐2‐nitroethylene (DHNE). Then, wide varieties of aldehydes are added to the mixture to afford the desired products good to excellent yields. This synthetic route is presented with several unique merits such as simplicity in operation and workup, readily presented starting materials, and high functional group tolerance. Additionally, the stoichiometric complex formation of these Schiff bases as ligand (L) with various metal ions [Mn(OAc)₂, Cu(OAc)₂ and Zn(OAc)₂] in general molecular formula [ML] is examined via Job's method. Subsequently, theoretical analysis of the product is accomplished using density functional theory (DFT) calculations. According to the frontier molecular orbital (FMO) analysis, it is found that the aryl group linked to the imine bond contributes as an electron donor in the ligand–metal complex.     

Dehydrogenative Carbon–Carbon Bond Formation Using Alkynyloxy Moieties as Hydrogen‐Accepting Directing Groups

In the presence of a catalyst system consisting of Pd(OAc)₂, PCy₃, and Zn(OAc)₂, the reaction of alkynyl aryl ethers with bicycloalkenes, α,ß‐unsaturated esters, or heteroarenes results in the site‐selective cleavage of two C? H bonds followed by the formation of C? C bonds. In all cases, the alkynyloxy group acts as a directing group for the activation of an ortho C? H bond and as a hydrogen acceptor, thus rendering the use of additives such as an oxidant or base unnecessary.     

Catalytic and regioselective synthesis of gem‐ or trans‐α,β‐unsaturated amides by carbonylation of alkyl alkynes with aniline derivatives by palladium(II) and phosphine

The reaction of carbonylative addition of alkyl alkynes to aniline derivatives has been successfully achieved by a catalytic system formed of Pd(OAc)₂ and a suitable bidentate phosphine ligand. The reaction led mainly to gem‐α,β‐unsaturated amides ( 3 ) with Pd(OAc)₂/1,3‐bis(diphenylphosphino)propane/p‐toluenesulfonic acid/CO as the catalytic system. However, the reaction catalyzed by Pd(OAc)₂/1,4‐bis(diphenylphosphino)butane/H₂/CO in CH₂Cl₂ as a solvent affords trans‐α,β‐unsaturated amides ( 4 ) as the major product. Copyright © 2003 John Wiley & Sons, Ltd.     

Nickel‐Catalyzed Conversion of Enol Triflates into Alkenyl Halides

A Ni‐catalyzed halogenation of enol triflates was developed and it enables the synthesis of a broad range of alkenyl iodides, bromides, and chlorides under mild reaction conditions. The reaction utilizes inexpensive, bench‐stable Ni(OAc)₂?4 H₂O as a precatalyst and proceeds at room temperature in the presence of sub‐stoichiometric Zn and either 1,5‐cyclooctadiene or 4‐(N,N‐dimethylamino)pyridine.     

A Transformation of N‐Alkylated Anilines to N‐Aryloxamates

Transformation of N‐alkylated anilines to N‐aryloxamates was studied using ethyl 2‐diazoacetoacetate as an alkylating agent and dirhodium tetraacetate (Rh₂(OAc)₄) as the catalyst. The general applicability of the reaction as a synthetic method for N‐aryloxamates was studied with a number of substituted N‐alkylated anilines. The results revealed that the oxamate was formed by a radical reaction with molecular O₂ and Rh₂(OAc)₄ as initiator.     

Oxidative Fragmentations of the 5α‐ and 5β‐Hydroxy‐B‐norcholestan‐ 3β‐yl Acetates

Oxidations of 5α‐hydroxy‐B‐norcholestan‐3β‐yl acetate ( 8 ) with Pb(OAc)₄ under thermal or photolytic conditions or in the presence of iodine afforded only complex mixtures of compounds. However, the HgO/I₂ version of the hypoiodite reaction gave as the primary products the stereoisomeric (Z)‐ and (E)‐1(10)‐unsaturated 5,10‐seco B‐nor‐derivatives 10 and 11 , and the stereoisomeric (5R,10R)‐ and (5S,10S)‐acetals 14 and 15 (Scheme 4). Further reaction of these compounds under conditions of their formation afforded, in addition, the A‐nor 1,5‐cyclization products 13 and 16 (from 10 ) and 12 (from 11 ) (see also Scheme 6) and the 6‐iodo‐5,6‐secolactones 17 and 19 (from 14 and 15 , resp.) and 4‐iodo‐4,5‐secolactone 18 (from 15 ) (see also Scheme 7). Oxidations of 5β‐hydroxy‐B‐norcholestan‐3β‐yl acetate ( 9 ) with both hypoiodite‐forming reagents (Pb(OAc)₄/I₂ and HgO/I₂) proceeded similarly to the HgO/I₂ reaction of the corresponding 5α‐hydroxy analogue 8 . Photolytic Pb(OAc)₄ oxidation of 9 afforded, in addition to the (Z)‐ and (E)‐5,10‐seco 1(10)‐unsaturated ketones 10 and 11 , their isomeric 5,10‐seco 10(19)‐unsaturated ketone 22 , the acetal 5‐acetate 21 , and 5β,19‐epoxy derivative 23 (Scheme 9). Exceptionally, in the thermal Pb(OAc)₄ oxidation of 9 , the 5,10‐seco ketones 10, 11 , and 22 were not formed, the only reaction being the stereoselective formation of the 5,10‐ethers with the β‐oriented epoxy bridge, i.e. the (10R)‐enol ether 20 and (5S,10R)‐acetal 5‐acetate 21 (Scheme 8). Possible mechanistic interpretations of the above transformations are discussed.     

Copper(II)‐Catalyzed Synthesis of N‐Substituted‐3‐amino‐4‐cyano‐isoquinoline‐1(2H)‐ones by the Reaction of N‐Substituted‐2‐iodobenzamides with Malononitrile

A novel Cu(OAc)₂·H₂O catalyzed coupling reaction of N‐substituted‐2‐iodobenzamides with malononitrile to afford N‐substituted‐3‐amino‐4‐cyano‐isoquinoline‐1(2H)‐ones is described. The reaction proceeded in DMSO at 90°C for 5 h in nitrogen without external ligands.     

An azide‐bridged copper(II) complex: poly[piperazine‐1,4‐dium [tetra‐μ3‐azido‐κ12N1:N1:N1‐hexa‐μ2‐azido‐κ12N1:N1‐di‐μ2‐azido‐κ4N1:N3‐pentacopper(II)] tetrahydrate]

A new Cu^II–azide complex, {(C₄H₁₂N₂)[Cu₅(N₃)₁₂]·4H₂O}_n, has been synthesized by the reaction of piperazine, Cu(OAc)₂·2H₂O (OAc is acetate) and NaN₃. In the structure, μ₂‐1,1‐ and μ₃‐1,1,1‐azide anions bridge five Cu^II cations to form a linear pentanuclear cluster unit, which is further linked by μ₂‐1,1‐ and μ₂‐1,3‐azide anions to form a two‐dimensional condensed [Cu₅(N₃)₁₂]_n layer. The diprotonated piperazine and the solvent water molecules are hydrogen bonded to the coordination layers to form a three‐dimensional supramolecular network.     

Preparations of Saturated N‐P‐N Type Secondary Phosphine Oxides and their Applications in Cross‐Coupling Reactions

A series of cyclohexane‐1,2‐diamine ( 3a – 3d ) and benzene‐1,2‐diamine derivatives ( 3e – 3h ) were pre‐ pared. Followed by hydrolysis, the reaction of 3a – 3c with PCl₃ successfully led to the formation of cor‐ responding metastable saturated heteroatom‐substituted secondary phosphine oxides (HASPO 4a – 4c ), a tautomer of the saturated heteroatom‐substituted phosphinous acid (HAPA). Whereas ambient‐stable diamine‐coordinated palladium complexes were obtained, HAPA‐coordinated palladium complexes were not successfully synthesized. The molecular structures of HASPO 4c , Pd(OAc)₂(3a) , PdBr₂(3b) and Pd(OAc)₂(3c) and [Cu(NO₃)(3d)⁺][NO₃ ^? ] were determined by single‐crystal X‐ray diffraction method. Catalysis of in‐situ Suzuki‐Miyaura cross‐coupling reactions for aryl bromides and phenylboronic acid using diamine 3a as ancillary ligand showed that the optimized reaction condition at 60 °C is the combination of 2 mmol % 3a /3.0 mmol KOH/1.0 mL 1,4‐dioxane/1 mmol % Pd(OAc)₂. Moreover, moderate reactivity was observed when using aryl chlorides as substrates (supporting infor‐ mation). When diamine 3d was employed in Heck reaction, good tolerance of functional groups of aryl bromides were observed while using 4‐bromoanisole and styrene as substrates. The optimized condi‐ tion for Heck reaction at 100 °C is 3 mmol % 3d /3.0 mmol CsF/1.0 mL toluene/3 mmol % Pd(OAc)₂. In general, cyclohexane‐1,2‐diamine derivatives exhibited better catalytic properties than those of benzene‐1,2‐diamines.     

NaY Zeolite Functionalized by Sulfamic Acid/Cu(OAc)2 as a Novel and Reusable Heterogeneous Hybrid Catalyst in Efficient Synthesis of Bis,Tris, and Tetrakis(indolyl)methanes, 3,4‐Dihydropyrimidin‐2(1H)‐ones,and 2‐Aryl‐1H‐benzothiazoles

An efficient acid‐catalyzed synthesis of some bis, tris, and tetrakis(indolyl)methanes, 3,4‐dihydropyrimidin‐2(1H )‐ones, and 2‐aryl‐1H ‐benzothiazoles is reported using NaY zeolite functionalized by sulfamic acid/Cu(OAc )₂ (NaY zeolite‐NHSO₃H /Cu(OAc )₂) in excellent yield. The heterogeneous catalyst has a simple work‐up procedure and could be recycled and reused for six reaction cycles.     

A three‐dimensional metal–organic polymer: poly[bis(μ2‐pyrimidine‐2‐thiolato‐κ4N1,S:S,N3)lead(II)]

The title compound, [Pb(C₄H₃N₂S)₂]_n, was prepared by the reaction of [Pb(OAc)₂]·3H₂O (OAc is acetate) with pyrimidine‐2‐thione in the presence of triethylamine in methanol. In the crystal structure, the Pb^II atom has an N₄S₄ coordination environment with four ligands coordinated by N‐ and S‐donor atoms. This compound shows that the pyrimidine‐2‐thiolate anion can lead to a three‐dimensional network when the coordination number of the metal ion can be higher than 6, as is the case with the Pb^II ion. This compound presents only covalent bonds, showing that despite the possibility of the hemidirected geometries of Pb^II, the eight‐coordinated ion does not allow the formation of an isolated molecular structure with pyrimidine‐2‐thiolate as the ligand.     

Cobalt‐Catalyzed,Aminoquinoline‐Directed C(sp2)H Bond Alkenylation by Alkynes

A method for cobalt‐catalyzed, aminoquinoline‐ and picolinamide‐directed C(sp²)? H bond alkenylation by alkynes was developed. The method shows excellent functional‐group tolerance and both internal and terminal alkynes are competent substrates for the coupling. The reaction employs a Co(OAc)₂?4 H₂O catalyst, Mn(OAc)₂ co‐catalyst, and oxygen (from air) as a terminal oxidant.     

Synthesis of poly(5,6‐difluoro‐2,1,3‐benzothiadiazole‐alt‐9,9‐dioctyl‐fluorene) via direct arylation polycondensation

Poly(5,6‐difluoro‐2,1,3‐benzothiadiazole‐alt‐9,9‐dioctylfluorene) was successfully synthesized via direct arylation polycondensation of 5,6‐difluoro‐2,1,3‐benzothiadiazole and 2,7‐dibromo‐9,9‐dioctylfluorene. The reaction conditions were optimized, and a polymer with number‐average molecular weight (M_n) of 41,000 was obtained by using Pd(OAc)₂, P^tBu₂Me‐HBF₄, pivalic acid, K₂CO₃, and toluene as catalyst, ligand, additive, base, and solvent, respectively. The polycondensation was also performed with 5,6‐dioctyloxy‐2,1,3‐benzothiadiazole or 2,1,3‐benzothiadiazole as the comonomer, and the results indicate that the introduction of electron‐withdrawing fluorine atoms at the ortho‐positions to the C? H bonds is essential for the reactivity of the direct arylation. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2367–2374     

6‐(Diazomethyl)‐1,3‐bis(methoxymethyl)uracil,Synthesis and Transformation into Annulated Pyrimidinediones

6‐(Diazomethyl)‐1,3‐bis(methoxymethyl)uracil ( 5 ) was prepared from the known aldehyde 3 by hydrazone formation and oxidation. Thermolysis of 5 and deprotection gave the pyrazolo[4,3‐d]pyrimidine‐5,7‐diones 7a and 7b . Rh₂(OAc)₄ catalyzed the transformation of 5 into to a 2 : 1 (Z)/(E) mixture of 1,2‐diuracilylethenes 9 (67%). Heating (Z)‐ 9 in 12n HCl at 95° led to electrocyclisation, oxidation, and deprotection to afford 73% of the pyrimido[5,4‐f]quinazolinetetraone 12 . The Rh₂(OAc)₄‐catalyzed reaction of 5 with 3,4‐dihydro‐2H‐pyran and 2,3‐dihydrofuran gave endo/exo‐mixtures of the 2‐oxabicyclo[4.1.0]heptane 13 (78%) and the 2‐oxabicyclo[3.1.0]hexane 15 (86%), Their treatment with AlCl₃ or Me₂AlCl promoted a vinylcyclopropane–cyclopentene rearrangement, leading to the pyrano‐ and furanocyclopenta[1,2‐d]pyrimidinediones 14 (88%) and 16 (51%), respectively. Similarly, the addition product of 5 to 2‐methoxypropene was transformed into the 5‐methylcyclopenta‐pyrimidinedione 18 (55%). The Rh₂(OAc)₄‐catalyzed reaction of 5 with thiophene gave the exo‐configured 2‐thiabicyclo[3.1.0]hexane 19 (69%). The analoguous reaction with furan led to 8‐oxabicyclo[3.2.1]oct‐2‐ene 20 (73%), and the reaction with (E)‐2‐styrylfuran yielded a diastereoisomeric mixture of hepta‐1,4,6‐trien‐3‐ones 21 (75%) that was transformed into the (1E,4E,6E)‐configured hepta‐1,4,6‐trien‐3‐one 21 (60%) at ambient temperature.     

Palladium‐Catalyzed Suzuki‐Miyaura Type Coupling Reaction of Aryl Halides with Triphenylborane‐Pyridine

The Suzuki‐Miyaura type coupling reaction of aryl halides with triphenylborane‐pyridine was described. The reaction can be catalyzed by Pd(OAc)₂ (5 mol%) in presence of Cs₂CO₃ at 50°C or 80°C, and functionalized biaryls were obtained in good to excellent yields. This protocol is general and can tolerate a wide range of functional groups.     

Palladium‐Catalyzed Enantioselective Cacchi Reaction: Asymmetric Synthesis of Axially Chiral 2,3‐Disubstituted Indoles

We report herein the first examples of a palladium‐catalyzed enantioselective Cacchi reaction for the synthesis of indoles bearing a chiral C2‐aryl axis. In the presence of a catalytic amount of Pd(OAc)₂ and (R,R)‐QuinoxP* ligand, reaction of N‐aryl(alkyl)sulfonyl‐2‐alkynylanilides with arylboronic acids under oxygen atmosphere afforded enantioenriched 2,3‐disubstituted indoles in high yields and enantioselectivity. The indole ring is constructed de novo in this process and a complexation‐induced chirality transfer is proposed to account for the observed enantioselectivity.     

An Efficient One‐Pot,Four‐Component Synthesis of {[(1H‐1,2,3‐Triazol‐4‐yl)methoxy]phenyl}‐1H‐pyrazolo[1,2‐b]phthalazine‐5,10‐dione Derivatives

The 1‐{[(1H‐1,2,3‐Triazol‐4‐yl)methoxy]phenyl}‐1H‐pyrazolo[1,2‐b]phthalazine‐5,10‐dione derivatives 5 were synthesized by a simple and efficient method, i.e., by the four‐component, one‐pot condensation reaction of phthalohydrazide 4 , a (propargyloxy)benzaldehyde 1 , an active methylene compound 3 (malononitrile or ethyl cyanoacetate), and an azide 2 in the presence of Cu(OAc)₂/sodium L ‐ascorbate as catalyst and 1‐methyl‐1H‐imidazolium trifluoroacetate ([Hmim](CF₃COO)) as an ionic‐liquid medium in good to excellent yields (Scheme 1).     

Orthopalladated complexes of phosphorus ylide: Poly(N‐vinyl‐2‐pyrrolidone)‐stabilized palladium nanoparticles as reusable heterogeneous catalyst for Suzuki and Heck cross‐coupling reactions

The phosphorus ylide [Ph₃PCHC(O)C₆H₄‐NO₂–4] reacted with Pd(OAc)₂ to give the C,C‐orthometallated complex [Pd{κ²(C,C)‐C₆H₄PPh₂C(H)CO(C₆H₄‐NO₂–4)}(μ‐OAc)]₂, which underwent bridge exchange reaction with NaN₃, NaCl, KBr and KI, respectively, to afford the binuclear C,C‐orthopalladated complexes [Pd{κ²(C,C)‐C₆H₄PPh₂C(H)CO(C₆H₄‐NO₂–4)}(μ‐X)]₂ (X = N₃ ( 1 ), Cl ( 2 ), Br ( 3 ) and I ( 4 )). The complexes were identified using spectroscopy (infrared and NMR), CHNS technique and single‐crystal X‐ray structure analysis. Thereafter, palladium nanoparticles with narrow size distribution were easily prepared using the refluxing reaction of iodo‐bridged orthopalladated complex 4 with poly(N ‐vinyl‐2‐pyrrolidone) (PVP) as the protecting group. The PVP‐stabilized palladium nanoparticles were characterized using a variety of techniques including X‐ray diffraction, transmission and scanning electron microscopies, energy‐dispersive X‐ray spectroscopy, inductively coupled plasma analysis and Fourier transform infrared spectroscopy. The catalytic activity of the PVP‐stabilized palladium nanoparticles was evaluated in the Suzuki reaction of phenylboronic acid and the Heck reaction of styrene with aryl halides of varying electron densities. This catalyst exhibited excellent catalytic activity for Suzuki cross‐coupling reactions in ethanol–water. Notably, aryl chlorides which are cheaper and more accessible than their bromide and iodide counterparts also reacted satisfactorily using this catalyst. After completion of reactions, the catalyst could be separated using a simple method and used many times in repeat cycles without considerable loss in its activity.