Halogen effects in Robinson-Gabriel type reaction of cyclopropanecarboxylic acid N′-substituted-hydrazides with PPh3/CX4

We found that the reaction of cyclopropanecarboxylic acid N′-substituted-hydrazides with PPh₃/CCl₄ proceeded smoothly to give the corresponding normal Robinson-Gabriel type product 2-cyclopropyl-5-substituted-[1,3,4]-oxadiazoles in good yields. Using CBr₄ or CI₄ instead of CCl₄ in the above system, the ring opening of cyclopropane occurred after dehydration to give the corresponding 2-(3-halopropyl)-5-substituted-[1,3,4]-oxadiazoles (4 or 5) in good yields.     

Chelate structures of 5-(H/Br)-2-hydroxybenzaldehyde-4-allyl-thiosemicarbazones (H2L): Synthesis and structural characterizations of [Ni(L)(PPh3)] and [Ru(HL)2(PPh3)2]

The reactions of 5-R-2-hydroxybenzaldehyde-4-allyl-thiosemicarbazone {R: H (L¹); Br (L²)} with [M^II(PPh₃)nCl₂] (M = Ni, n = 2 and M = Ru, n = 3) in a 1:1 molar ratio have given stable solid complexes corresponding to the general formula [Ni(L)(PPh₃)] and [Ru(HL)₂(PPh₃)₂]. While the 1:1 nickel complexes are formed from an ONS donor set of the thiosemicarbazone and the P atom of triphenylphosphine in a square planar structure, the 1:2 ruthenium complexes consist of a couple from each of N, S and P donor atoms in a distorted octahedral geometry. These mixed-ligand complexes have been characterized by elemental analysis, IR, UV–Vis, APCI-MS, ¹H and ³¹P NMR spectroscopies. The structures of [Ni(L²)(PPh₃)] (II) and [Ru(L¹H)₂(PPh₃)₂] (III) were determined by single crystal X-ray diffraction.     

Assembly of 3-sulfonated 2H-pyrrol-2-ones through the insertion of sulfur dioxide with allenoic amides

Generation of 3-sulfonated 2H-pyrrol-2-ones through a three-component reaction of allenoic amides, sulfur dioxide, and aryldiazonium tetrafluoroborates under metal-free conditions is achieved. This transformation proceeds under mild conditions without the addition of catalysts or additives, giving rise to 3-sulfonated 2H-pyrrol-2-ones in moderate to good yields. Good functional group compatibility is observed. A plausible mechanism is proposed, which is initiated by aryl radicals formed in situ from aryldiazonium tetrafluoroborates and DABCO·(SO₂)₂. Additionally, excellent chemoselectivity and regioselectivity are presented in this transformation.     

Synthesis,characterization and antimicrobial studies of mixed ligand silver(I) complexes of thioureas and triphenylphosphine; crystal structure of {[Ag(PPh3)(thiourea)(NO3)]2·[Ag(PPh3)(thiourea)]2(NO3)2}

Mixed ligand silver(I) complexes of triphenylphosphine and thioureas (thiourea (Tu), N-methylthiourea (Metu), N,N′-dimethylthiourea (Dmtu) and N,N′-diethylthiourea (Detu)) with the general formulae, [(Ph₃P)₂Ag(thione)]NO₃ and [(Ph₃P)Ag(thione)₂]NO₃, have been prepared and characterized by elemental analysis, IR and NMR (¹H, ¹³C and ³¹P) spectroscopic methods. The crystal structure of one of them has been determined by X-ray crystallography. The spectral data of the complexes are consistent with sulfur coordination of the thiones to silver(I). The single crystal X-ray structure of complex 1, {[Ag(PPh₃)(thiourea)(NO₃)]₂·[Ag(PPh₃)(thiourea)]₂(NO₃)₂}, shows that the complex consists of two independent centrosymmetric binuclear units, each having the silver atoms coordinated to one PPh₃ and two bridging thiourea molecules. In one of the independent units the silver atom is additionally bound to a nitrate ion, leading to a tetrahedral geometry, while in the other unit the silver atom adopts a trigonal planar environment. Antimicrobial activities of the complexes were evaluated by their minimum inhibitory concentration and the results showed that the complexes show a wide range of activity against two gram-negative bacteria (Escherichiacoli, Pseudomonasaeruginosa) and molds (Aspergillusniger, Penicilliumcitrinum), while the activities were poor against yeasts (Candidaalbicans, Saccharomycescerevisiae). However, the title complex did not show activity against any tested microorganism.     

A novel method for the reduction of sulfoxides with the N,N,N’,N’-tetrabromobenzene-1,3-disulfonamide (TBBDA)/PPh3 system

A new method is described for the reduction of sulfoxides to sulfides using N,N,N’,N’-tetrabromobenzene-1,3-disulfonamide [TBBDA] in combination with triphenylphosphine. Good to excellent yields, short reaction times, high efficiency and facile isolation of the desired products are the advantages of this method.     

Efficient microwave syntheses of the compounds Os3(CO)11L, L = NCMe, py, PPh3

The results of simple microwave-assisted ligand substitution reactions of Os₃(CO)₁₂ are reported. In a remarkably short period of time, the labile complex Os₃(CO)₁₁(NCMe) is prepared in high yield without the need for a decarbonylation reagent such as trimethylamine oxide. Microwave irradiation of Os₃(CO)₁₂ in a relatively small amount of acetonitrile is shown to be a useful first step in two-step, one-pot syntheses of the cluster complexes Os₃(CO)₁₁(py) and Os₃(CO)₁₁(PPh₃).     

Phenoxide-assisted P-C bond cleavage in PdCl2(PPh3)2 under very mild conditions

PdCl₂(PPh₃)₂ reacted with NaOAr (Ar = Ph, p-tolyl) at 0 °C to afford PdCl(Ph)(PPh₃)₂, instead of PdCl(OAr)(PPh₃)₂, in 12-16% isolated yields based on Pd. The structure was confirmed by NMR and X-ray crystallography. GC-MS analysis of the reaction solution revealed that OPPh₂(OAr), OPPh(OAr)₂, and OP(OAr)₃ are formed, while NMR studies indicated that PdCl(Ph)(PPh₃)₂ is produced when PdCl(OAr)(PPh₃)₂ decomposes. The reaction of PdCl₂(PPh₃)₂ with Bu₃Sn(OC₆H₄-p-OMe) also gave PdCl(Ph)(PPh₃)₂ in 8% isolated yield. These results suggest that PdCl(OAr)(PPh₃)₂ is highly labile and the aryloxy ligand exchanges with the phenyl groups in triphenylphosphine even under very mild conditions.     

Pd(PPh3)4-catalyzed direct ortho-fluorination of 2-arylbenzothiazoles with an electrophilic fluoride N-fluorobenzenesulfonimide (NFSI)

An efficient protocol was developed for regio-selective Pd-catalyzed direct ortho-fluorination of 2-arylbenzo[d]thiazoles using N-fluorobenzenesulfonimide (NFSI) as the F⁺ source, and l-proline as the crucial promoter. The present method offered a practical route to synthesize valuable fluorinated products, which are of potential importance in the pharmaceutical and agrochemical industries.     

Synthesis of 4-allylquinazolines from N-(2-cyanoaryl)amides via the In-mediated allylation of nitrile and dehydrative cyclization cascade

The reaction of allylindium reagents and N-(2-cyanoaryl)amides afforded 2-substituted-4-allylquinazolines in good yields via the indium-mediated Barbier-type allylation of nitrile and the following dehydrative cyclization cascade.     

Effect of oxyethylene groups on the behaviour of thermodynamic properties of pyrrolidin-2-one and poly(ethylene glycols)

Dilatometric measurements of excess volume V^E and ultrasonic speed u have been carried out for mixtures of mono-, di-, tri- and tetra(ethylene glycol)s in pyrrolidin-2-one (PY) over the whole mole fraction range at 303.15 K. In the mixture of PY and monoethylene glycol, the V^E is positive except for slight negative variation at the high mole fraction of PY. The other three mixtures PY + di-, + tri- and + tetra(ethylene glycol)s show negative V^E over the entire composition range in the order di-u with increase in the mole fraction of PY in the case of monoethylene glycol while for other three systems u rises. From these measurements, partial molar quantities V_i^E and K_S,i^E have been calculated and analysed. Estimates of isentropic molar quantity K_S equal to −(∂V/∂p)_S and its excess counterpart K_S^E have also been computed. The K_S^E is positive for mono-, and negative for all the other mixtures over the whole composition range.     

Chemistry of polyfunctional molecules-123. Reactions of BiBr3, SbI3 and AsI3 with LiN(PPh2)2; X-ray structure of a cyclophosphazene salt containing arsenic(I)

BiBr₃ or SbI₃ react at 20°C with LiN(PPh₂)₂ (1) to give elementary Bi or Sb and the P---P coupled phosphazene ligand Ph₂P---N=PPh₂---PPh₂=N---PPh₂ (2). The reaction of AsI₃ with 1 at room temperature formed yellow needles of the eight-membered heterocycle (3), whereas AsI₃ interacted at 80°C with 1 in the molar ratio of 1:3 to give elementary arsenic and 2. Treatment of AsI₃ and 1 at 20°C in a 1:2 stoichiometry yielded the seven-membered, cyclic arsenium(I) salt

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I·4THF (5·4THF), which was characterized by elemental analysis, conductivity, mass, IR and NMR spectroscopy and single-crystal X-ray structural analysis.     

Synthesis and characterization of isomanolonitrile dithiolato palladium complexes. Crystal structure of (PPh3)2Pd(S2C4N2) and (Et4N)2WS4Pd(S2C4N2)

A series of isomalononitrile dithiolato palladium complexes, (PPh₃)₂Pd(1-mnt) (1), [P(OPh)₃]₂Pd(i-mnt) (2), (PPh₃)(py)Pd(i-mnt)·CH₃CN (4), (Et₄N)₂Pd(i-mnt)₂ (4) and (Ph₄As)₂Pd(i-mnt)₂ (5) were synthesized and characterized by elemental analysis and IR spectroscopy. The reaction between (Et₄N)₂Pd(i-mnt)₂ (4) and (Et₄N)₂WS₄ gave a mixed metal cluster (Et₄N)₂WS₄Pd(i-mnt) (6). The crystallographically determined structures of 1 and 6 are reported.     

Ph3P/Br2/n-Bu4NNO2 as an efficient system for the preparation of N-nitrosamines and azides

The combination PPh₃/Br₂/n-Bu₄NNO₂ was developed as a new reagent system for the efficient preparation of N-nitrosamines and azides from the corresponding amines and hydrazine derivatives, respectively, at 0 °C to room temperature, in excellent yields.     

Photochemical reaction of W(CO)6 with SnCl4 II. Synthesis and X-ray structure of tetrachlorobis(triphenylphosphine oxide)tungsten(IV), [WCl4(OPPh3)2]

The crystal structure of [WCl₄(OPPh₃)₂](1), formed in the photochemical reaction of W(CO)₆ with SnCl₄ in the presence of triphenylphosphine, has been determined by the single-crystal X-ray diffraction method. The compound crystallizes in the monoclinic space C2/c, with A=14.027(3), B=13.163(3), C=19.621(4) Å, β=96.36(3)°, Z=4. The structure solved by heavy-atom methods has been refined to R=0.0466, for 3489 observed reflections.

The [WCl₄(OPPh₃)₂] molecule possesses a crystallographically imposed C₂ axis passing through the tungsten atom. Despite steric demands, a mutually cis arrangement of triphenylphosphine oxide oxygens is found for [WCl₄(OPPh₃)₂], while there is a slight lengthening of the W---Cl bonds trans to the oxygen atoms.     

原位产生的SO42-配位的二维无机钴配合物K2[Co3(OH)2(SO4)3(H2O)2]的水热合成及晶体结构

相同的水热反应条件下4-氨基-二(2-吡啶基)-1，2，4-三氮唑(abpt)、KSCN与钴盐(CoCl₂·6H₂O)反应合成了2种新的钴配合物:零维的单核配合物[CoSCN(abpt)] (1α)和二维的无机层状配合物K₂[Co₃(OH)₂(SO₄)₃(H₂O)₂] (1β)，并通过元素分析和红外光谱对其进行了表征。配合物1α的晶体属于单斜晶系，P2₁/c空间群。配合物1β晶体属于正交晶系，Cmc2₁空间群。在配合物1α中，abpt和SCN^-配体都参与配位与Co(Ⅱ)离子形成了2个不同的单核单元，这些单核单元又通过S原子和N原子之间的氢键作用连成了三维超分子结构;在配合物1β中，abpt配体没有参与配位，而SCN^-配体则被氧化成了SO₄^2-离子并与Co(Ⅱ)离子配位形成了二维配位层状结构，相邻层之间进一步通过氢键作用形成了沿c轴方向有孔道的三维超分子网络，这些孔道里面填充着反离子K+。     

[Cu(TO)2(H2O)4](PA)2的合成和晶体结构

[Cu(TO)₂(H₂O)₄](PA)₂ was prepared by mixing the aqueous solution of 1,2,4-triazol-5-one(TO) and Cu(PA)₂. The molecular structure and crystal structure of the title complex was determined by X-ray single crystal diffraction method. The crystal is triclinic, space group with a=0.7321(1)nm,b=0.7474(2)nm,c=1.3649(3)nm;α=88.65(2)°,β=85.63(1)°,γ=63.35(1)°;V=0.6655(2)nm³,Z=1. The Cu²⁺ coordinated with two TO molecule through its 2-nitrogen atom and four water molecules and showed an octahedral configuration.     

Monomeric and dimeric ruthenium thiooxalate complexes: Structures of CpRu(PPh3)2SCOCO2Me and CpRu(dppe)SCOCO2Et

The hydrosulfido complexes CpRu(L)(L′)SH react with one equivalent of O-alkyl oxalyl chlorides (ROCOCOCl) to form the corresponding O-alkylthiooxalate complexes CpRu(L)(L′)SCOCO₂R (L = L′ = PPh₃ (1), (2); L = PPh₃, L′ = CO (3); R = Me (a), Et (b)). The reactions of the hydrosulfido complexes with half equivalent of oxalyl chloride produce the bimetallic complexes [CpRu(L)(L′)SCO]₂ (L = L′ = PPh₃ (4), (5); L = PPh₃, L′ = CO (6)). The crystal structures of CpRu(PPh₃)₂SCOCO₂Me (1a) and CpRu(dppe)SCOCO₂Et (2b) are reported.     

Pd2dba3/P(i-BuNCH2CH2)3N: a highly efficient catalyst for the one-pot synthesis of trans-4-N,N-diarylaminostilbenes and N,N-diarylaminostyrenes

A Pd₂dba₃/P(i-BuNCH₂CH₂)₃N catalyzed one-pot synthesis of unsymmetrically substituted trans-4-N,N-diarylaminostilbenes and both symmetrically and unsymmetrically substituted N,N-diarylaminostyrene derivatives is reported. The procedure involves two or more palladium catalyzed sequential coupling reactions (an amination and an inter-molecular Heck reaction) in one-pot using the same catalyst system with two different aryl halides, including aryl chlorides and hetero aryl halides as the coupling partners.     

Competitive thermal ene reaction and Diels-Alder reactions of 2-[N-(alk-2-enyl)benzylamino]-3-vinylpyrido[1,2-a]pyrimidin-4(4H)-ones

Thermal reaction of 2-[N-(alk-2-enyl)benzylamino]-3-(2-substituted and 2,2-disubstituted)vinylpyrido[1,2-a]pyrimidin-4(4H)-ones gave azepine, the desired ene products, and/or pyran derivatives. The formation of the latter was responsible for the [4+2] cycloaddition reaction between the α,β-unsaturated ester carbonyl moiety as a diene part and the alkenylamino moiety as an ene one. The reaction features depended upon the kinds of substituents both on the vinyl and alkenyl counterparts; strongly electron-withdrawing substituents on the vinyl moiety or an electron-donating substituent on the alkenyl one changed the reaction feature from the ene reaction to the hetero Diels-Alder reaction.     

Structure and bonding in a series of cyano complexes: RuCp(PPh3) 2CN, [RuCp(PPh3) 2(CNH)]CF3SO3, and H-bridged [Ru2(Cp) 2(PPh3) 4CNHNC]CF3SO3

The three title cyanoruthenium complexes have been characterized by means of X-ray diffraction analysis, IR and NMR solution spectroscopies, as well as extended Hückel molecular orbital calculations examining the properties of the cyanide fragment changing with complexation and with the co-ligands Cp and PPh₃. Explanations are given for crystallographic results of the C-N bond shortening upon complexation, the supershort (2.573 Å) bond length of N(H) N in the bridged complex, as well as the Ru-C-N and C-N-H-N-C bendings. Although the crystallographically found asymmetry of coordinated Cp is not significant, the MO calculations suggest a distorted endocyclic bond-length pattern indicative of the relative importance of σ and π bonding in the metalcyclopentadienyl interactions.