Presence Of ZnBr2 Research Articles

Direct oxidative carboxylation of olefins into cyclic carbonates at ambient pressure

The direct synthesis of cyclic carbonate from carbon dioxide (CO2) and olefins is attracting much interest in recent years. Herein, 1,5,7-triazabicyclo[4.4.0]dec-5-ene-functionalized phosphonate salts have been synthesized and characterized fully by Nuclear Magnetic Resonance (NMR), Electrospray Ionization Mass Spectrometry (ESI-MS) and Fourier Transform-infrared Spectroscopy (FT-IR) etc. The as-obtained salts have been employed as efficient catalysts for one-pot synthesis of cyclic carbonate from styrene and CO2 through oxidative carboxylation reaction under very mild conditions (0.1 MPa CO2, 80 °C) without any other solvents. The yield of cyclic carbonate can reach up to ca. 70 % in the presence of ZnBr2 under the mild reaction condition. Besides, the catalyst can be recycled at least five times without significantly losing its catalytic activity. This approach can be extended to various styrene derivatives and good yields of cyclic carbonates was achieved under ambient conditions. Based on activity evaluation, reaction kinetics and DFT calculation, the six-membered carboxyphosphate species was proposed as a crucial intermediate species and played a crucial role in CO2 activation. Finally, the reaction mechanism is proposed accordingly.

Experimental investigation on thermochemical sulfate reduction in the presence of 1-pentanethiol at 200 and 250 °C: Implications for in situ TSR processes occurring in some MVT deposits

Organic sulfur compounds are ubiquitous in natural oil and gas fields and moderate-low temperature sulfide ore deposits. Previous studies have shown that organic sulfur compounds are important in enhancing the rates of thermochemical sulfate reduction (TSR) reactions, but the details of these reaction mechanisms remain unclear. In order to assess the extent of sulfate reduction in the presence of labile sulfur species at temperature conditions near to those where TSR occurs in nature, we conducted a series of experiments using the fused silica capillary capsule (FCSS) method. The tested systems containing labile sulfur species are MgSO4 + 1-pentanethiol (C5H11SH) + 1-octene (C8H16), MgSO4+1-octene (C8H16), MgSO4+1-pentanethiol (C5H11SH), 1-pentanethiol (C5H11SH)+H2O, and MgSO4 + 1-pentanethiol (C5H11SH) + ZnBr2 systems. Our results show that: (1) intermediate oxidized carbon species (ethanol and acetic acid) are formed during TSR simulation experiments when 1-pentanethiol is present; (2) in the presence of ZnBr2, 1-pentanethiol can be oxidized by sulfate to CO2 at 200 °C, which is within the temperature range observed in natural TSR; and (3) the precipitation of sulfide minerals may significantly promote the rate of TSR, indicating that the rates of in situ TSR reactions in ore deposits could be much faster than previously thought. This may be important for understanding the possibility of in situ TSR as a mechanism for the precipitation of metal sulfides in some ore deposits. These findings provide important experimental evidence for understanding the role of organic sulfur compounds in TSR reactions and the pathway of TSR reactions initiated by organic sulfur compounds under natural conditions.

Palladium-catalyzed nucleophilic allylic substitution of Morita–Baylis–Hillman adducts with enamines: Synthesis of 1,5-dicarbonyl compounds

An efficient nucleophilic allylic substitution of a variety of Morita–Baylis–Hillman adducts with enamines catalyzed by Pd(OAc) 2 in the presence of ZnBr 2 as a promoter is described in the present study. The reaction gives S N 2-type 1,5-dicarbonyl compounds that may subsequently undergo an intramolecular conjugate addition onto the enone moiety affording the corresponding 1,4-adducts. All the synthesized compounds have been isolated in moderate to good yields and fully characterized.

ZnBr2-Mediated Cascade Reaction of o-Alkoxy Alkynols: Synthesis of Indeno[1,2-c]chromenes.

A Lewis acid-mediated cascade annulation of o-alkoxy alkynols in the presence of ZnBr2 has been developed. The cascade cyclization proceeds through a 5-exo-dig cyclization followed by a Friedel-Crafts reaction and ring-opening sequence to synthesize indeno[1,2-c]chromenes. This protocol provides a broad substrate scope in moderate to good yields with high regioselectivity. The reaction with benzo-fused cycloalkyl ketones gave an unexpected alkyne C-C bond cleavage resulting in fused polycycles.

3-Bromo-2-Pyrone: An Alternative and Convenient Route to Functionalized Phosphinines.

The facile access to 3-bromo-2-pyrone allows the preparation of 6-bromo-2-trimethylsilyl-phosphinine by a [4+2] cycloaddition with Me3 Si-C≡P for the first time. The regioselectivity of this reaction could be verified by means of single crystal X-ray diffraction of the corresponding W(0) complex. In the presence of ZnBr2 and dppp (1,3-bis(diphenylphosphino)propane) as a bidentate ligand, the bromo-phosphinine quantitatively undergoes a Negishi cross-coupling reaction with PhLi that selectively leads to 6-phenyl-2-trimethylsilyl-phosphinine. This heterocycle could again be characterized by means of X-ray diffraction as a W(0) complex. These results describe a new and convenient route to 2,6-disubstituted phosphinines that makes use of readily available starting materials.

Unusual Reactivity of Aryl Aldehydes with Triethyl Phosphite and Zinc Bromide: A Facile Preparation of Epoxides, Benzisoxazoles, and α‐Hydroxy Phosphonate Esters

AbstractA facile preparation of trans‐epoxides was achieved by a (EtO)3P–ZnBr2‐mediated deoxygenation reaction of the corresponding 2‐nitrobenzaldehydes. The sterically hindered analogues of 2‐nitrobenzaldehyde underwent a reaction with triethyl phosphite in the presence of ZnBr2 as the catalyst to form benzisoxazoles as the sole product. Under identical conditions, the reactions of electron‐rich as well as moderately electron‐deficient aryl aldehydes furnished the corresponding α‐hydroxy phosphonate esters.

ChemInform Abstract: Aerobic Cross‐Dehydrogenative Coupling of Terminal Alkynes and Tertiary Amines by a Combined Catalyst of Zn2+ and OMS‐2.

AbstractIn the presence of ZnBr2 and manganese oxide‐based octahedral molecular sieves (OMS‐2), structurally diverse propargylamines are synthesized by this new coupling reaction using molecular oxygen as the terminal oxidant which provides a green synthetic route to the title compounds.

Kinetics and Mechanistic Insight into Efficient Fixation of CO2 to Epoxides over N-Heterocyclic Compound/ZnBr2 Catalysts

In this contribution, a series of N-heterocyclic compounds cooperated with ZnBr2 catalyst for chemical fixation of CO2 to cyclic carbonates was developed without utilization of additional organic solvents. It was found that the catalytic activity of N-heterocyclic compounds could be obviously enhanced in the presence of ZnBr2, and the N-methylimidazole (Mim)/ZnBr2 catalytic system was the most efficient among the catalysts employed. Under the optimum reaction conditions, 99% yield of propylene carbonate was achieved with TOF of 474 h–1, and the catalysts were also versatile for CO2 cycloaddition with less active epoxides such as styrene oxide and cyclohexene oxide. Furthermore, a possible synergistic catalytic mechanism was proposed. Moreover, the rate constants were determined as a function of reaction temperature in the range of 130–160 °C, the activation energy was determined to be 41.1 kJ·mol–1, and the kinetic equation on the synthesis of propylene carbonate catalyzed by Mim/ZnBr2 was also obtained.

Synthesis of cyclic carbonate from allyl glycidyl ether and carbon dioxide using ionic liquid-functionalized amorphous silica

Ionic liquid functionalized mesoporous silica (IFMS) was prepared from the coupling of 1-(triethoxysilylpropyl)-3- n-alkylimidazolium halides with tetraethyl orthosilicate (TEOS) through template-free condensation under strong acidic conditions. The immobilized ionic liquid (IM-IL) catalysts showed 0.61–0.93 mmol of ionic liquid on SiO 2 and surface area in the range of 189–647 m 2/g with pore sizes from 3.2 to 4.2 nm. Elemental analysis and SEM image showed that the immobilized ionic liquid groups were well incorporated on the support. The silica-supported ionic liquids were proved to be an effective heterogeneous catalyst for the solventless synthesis of cyclic carbonate from allyl glycidyl ether (AGE) and carbon dioxide. Im-IL of longer alkyl chain length and more nucleophilic nature showed higher conversion of AGE. High temperature, high carbon dioxide pressure, and the presence of ZnBr 2 co-catalyst were favorable for the conversion of AGE. Im-IL can be reused for the reaction up to three consecutive runs without any considerable loss of its catalytic activity.

Synthesis of N‐(1H)‐Tetrazole Sulfoximines.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Synthesis of N-(1H)-Tetrazole Sulfoximines

N-(1H)-Tetrazole sulfoximines are readily available by addition of sodium azide to the corresponding N-cyano derivatives in the presence of ZnBr2. The use of these N-(1H)-tetrazoles as intermediates in the synthesis of other N-heterocyclic sulfoximines is demonstrated.

ZnBr2‐Catalyzed Efficient Oxidative Homo Coupling of Aryl Magnesium Bromides.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

ZnBr2‐Catalyzed Efficient Oxidative Homo Coupling of Aryl Magnesium Bromides

Oxidative homo coupling of various arylmagnesium bromides in the presence of ZnBr2 gave the corresponding symmetrical biaryls in moderate to good yields at room temperature. An efficient method under mild conditions without the use of reoxidant is described. IICT Communication No. 050507

Serendipitous Synthesis of Unusual Cyclic and Acyclic Enaminone Esters from Tröger’s Base and Conjugated Esters

The reaction of Tröger’s base and methyl propiolate in the presence of ZnBr2 in CH3CN serendipitously afforded unusual cyclic enaminone ester derivatives in moderate to good yields.

Zinc- and Indium-Promoted Conjugate Addition−Cyclization Reactions of Ethenetricarboxylates with Propargylamines and Alcohol: Novel Methylenepyrrolidine and Methylenetetrahydrofuran Syntheses

A new zinc- and indium-promoted conjugate addition-cyclization reaction to afford nitrogen- and oxygen-containing five-membered heterocycles has been developed. Reaction of ethenetricarboxylates with propargylamines (1 equiv) in the presence of ZnBr2 or InBr3 afforded methylenepyrrolidines in high yields. The stoichiometric use of ZnBr2 or InBr3 at room temperature and the catalytic use of InBr3-Et3N at 80 degrees C were effective. Reaction of ethenetricarboxylates with propargyl alcohol in the presence of ZnBr2 or InBr3 afforded methylenetetrahydrofurans.

First highly stereoselective synthesis of anti-α-trifluoromethyl-β-amino acid derivatives

The Reformatsky-type reaction of 2-bromo-3,3,3-trifluoropropanoic imide with various types of imines, in the presence of ZnBr2 as a Lewis acid in THF at 0 degrees C for 3 h, gave the corresponding alpha-trifluoromethyl-beta-amino acid derivatives in a highly anti-selective manner.

Facile Synthesis of α,β‐Acetylenic Ketones and 2,5‐Disubstituted Furans: Consecutive Activation of Triple and Double Bond with ZnBr2 Toward the Synthesis of Furan Ring.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Formation of upper rim acylated calix[4]arenes using a sacrificial zinc anode

A straightforward electrosynthetic method is described, which allows upper rim acylation of non- p-halogenated calix[4]arenes. For example, a solution of tetrapropoxycalix[4]arene 4 was electrolysed in the presence of ZnBr 2 in an undivided cell fitted with a sacrificial zinc anode using pure acetonitrile as solvent, yielding an organozinc species, which was then treated with acetyl chloride in the presence of a palladium catalyst to afford 5,11-diacetyl-25,26,27,28-tetrapropoxycalix[4]arene 5 in ca. 35% yield after workup.

Efficient Introduction of Aryl Acetylenes to Quinolinium and Pyridinium Salts: Synthesis of 1‐Acyl‐1,2‐dihydroquinolines and 1‐Acyl‐1,2‐dihydropyridines.

Recently, we reported the alkynylation of N-tosylimines with aryl acetylenes promoted by ZnBr2 and N,N-diisopropylethylamine (DIEA) in acetonitrile. In the reaction, in situ generated zinc acetylide was added to N-tosylimine to afford the corresponding N-tosyl propargylamines in good yields. As a continuing work we presumed that we could synthesize 1-acyl-1,2-dihydroquinolines and 1-acyl-1,2dihydropyridines when we used 1-acylquinolinium salts or 1-acylpyridinium salts as the electrophile. Synthesis of 1-acyl-1,2-dihydroquinolines and 1-acyl-1,2dihydropyridines have received much attention due to the usefulness of them for the synthesis of natural products and as useful building blocks for alkaloid synthesis. The most straightforward method for the synthesis of substituted dihydroquinolines and dihydropyridines is the addition of Grignard reagents to 1-acylquinolinium and 1-acylpyridinium salts. Besides organomagnesium reagents, other organometallic reagents involving indium, tin, silver, copper, and zinc were reported as the efficient reagents for the reaction. However, the addition of alkynyl moiety to 1-acylquinolinium or 1-acylpyridinium salts was rather limited. Initially, we tried the reaction of 1-ethoxycarbonylquinolinium chloride and phenylacetylene in acetonitrile in the presence of ZnBr2 and DIEA (N,N-diisopropylethylamine, Hunig’s base) as shown in Scheme 1. The starting material 1-ethoxycarbonylquinolinium chloride was generated in situ instantaneously by simply mixing quinoline (1a) and ethyl chloroformate in acetonitrile at room temperature. As expected we obtained 1-ethoxycarbonyl-1,2-dihydroquinoline derivative 2a in 70% isolated yield. Encouraged by the successful results we tried other entries as shown in Table 1 and obtained moderate to good yields of products. As the substrates, we examined quinoline (entries 1-4), pyridine (entries 5-6), and isoquinoline (entry 7). We used ethyl chloroformate (entries 1-3, 5, 7) and benzoyl chloride (entries 4 and 6) as the activators. As the acetylenes, we chose phenylacetylene (entries 1, 4-7), 4-ethynyltoluene (entry 2), and 1-ethynyl-4-methoxybenzene (entry 3) as the representative examples. As shown in Table 1, we obtained the desired products 2a-g in 63-79% isolated yields. Identification of the structure of 2a-g was carried out by their IR, H and C NMR spectra, mass, and/or by comparison with the reported data. The H and C NMR spectra showed broad peaks in some cases presumably due to the line broadening effect of nitrogen atom as easily can be seen in a similar system. In summary, we disclosed in this paper that the combination of aryl acetylene, ZnBr2, and DIEA could be used for the efficient introduction of acetylene moiety toward activated pyridines, quinolines, and isoquinolines.

Facile synthesis of α,β-acetylenic ketones and 2,5-disubstituted furans: consecutive activation of triple and double bond with ZnBr 2 toward the synthesis of furan ring

α,β -Acetylenic ketones were synthesized from the reaction of acid chlorides and acetylenic compounds in the presence of ZnBr 2 and DIEA in acetonitrile. From the acetylenic ketones having nearby methylene unit, 2,5-disubstituted furan derivatives could be synthesized under the same reaction conditions.