Acetate 1a Research Articles

Simple thiazole-based ligands for palladium(II) Suzuki-Miyaura aryl cross-coupling catalysts

Two new palladium(II) catalysts, each containing a phenylthiazole ligand (2-methyl- (1a) and 2-amino-4-phenyl-1,3-thiazole (1b)) are prepared and characterized. The crystal structure of one, 2-methyl-4-phenyl)palladium(II) acetate (3a), is presented; it crystallizes as a dimer, with the ligand attached through the nitrogen on the thiazole and the ortho-carbon on the phenyl ring. The organometallic compounds can be used as catalysts in Suzuki-Miyaura aryl cross-coupling reactions. They are compatible with a wide range of functional groups, including carbonyls, amines, and phenols.

Synthesis, Anticancer, Antioxidant, Anti-Inflammatory, Antimicrobial Activities, Molecular Docking, and DFT Studies of Sultams Derived from Saccharin.

A series of N-substituted saccharins namely 2-(1,1-dioxido-3-oxobenzo[d]isothiazol-2(3H)-yl) acetonitrile (2) and (alkyl 1,1-dioxido-3-oxobenzo[d]isothiazol-2(3H)-yl) acetate (3a–g) were synthesized, in moderate to excellent yields, from commercially available starting materials by two different approaches and their chemical structures were characterized by spectroscopic techniques (1H-NMR, 13C-NMR, IR, and MS). All the synthesized compounds were evaluated for their anti-inflammatory toward IL-6 and TNF-α, antioxidant, as well as their anticancer activities against hepatic cancer cells. In addition, their anti-fungal and antibacterial activities against both Gram-positive and Gram-negative bacteria were tested. All the tested compounds have exhibited excellent (3a, d, e) to moderate anti-inflammatory activity. Additionally, esters (3b, f) and nitrile (2) showed excellent antioxidant activity. Furthermore, ester 3f, with isopropyl ester, exhibited the highest cytotoxic activity compared to the other esters. Moreover, all compounds were evaluated as selective inhibitors of the human COX-1 enzyme using molecular docking by calculating the free energy of binding, inhibition constant, and other parameters to find out the binding affinity. The molecular study showed that esters (3d, f) and nitrile (2) revealed the highest binding affinities, hence enhancing the inhibition activity with the active site of the COX-1 enzyme. All the tested compounds have more negative Gibbs free, electrostatic, and total intermolecular energies than the standard inhibitor ASA. These results indicate that, all the tested sultams are potent anti-inflammatory drugs as compared to standard inhibitors. Finally, the chemical properties and the quantum factors of synthesized sultams were calculated based on density functional theory (DFT) to predict reactivity, and then correlated with the experimental data. Ester 3f showed the lowest ionization potential and lowest energy gap (Egap = 7.5691 eV), which was correlated with its cytotoxic activity. Furthermore, the spatial electron distribution of HOMO, LUMO were computed and it clearly indicates the electron donation ability of all the tested compounds.

Enantioselective bio-deacylation of arylalkyl acetates using tertiary amines as additive under promiscuous conditions

Herein, we describe the impact of the introduction of tertiary amines as additive during the enzymatic kinetic resolution via deacylation of some arylalkyl acetates 1a-8a under promiscuous conditions. Two CAL-B preparations were examined: Novozym®435 and CHIRAZYME® L-2, c.-f. C2, lyo. The influence of the introduction of seven amines is checked: Triethylamine (Et3N), Pyridine, 4-Dimethylaminopyridine (4-DMAP), 1,4-Diazabicyclo[2.2.2]octane (DABCO), Cinchonine, Cinchonidine, Quinine and Quinidine; and that in two organic solvent: diisopropylether (DIPE) and tertiobutylmethyl ether (TBME).Among the examined amines, the use of DABCO as additive recorded the best results in terms of reactivity and selectivity. It was to be highlighted that this additive was reported as an enzyme activator for the first time in the enzymatic kinetic resolution via hydrolysis of racemic acetates under non-aqueous conditions. Both CAL-B preparations showed the same behavior in the presence of the chosen additives during the biodeacylation of the resolved acetates. No direct correlation between the pKa values of several used additives and the CAL-B activation rates has been revealed.An ideal enzymatic kinetic resolution was recorded with the acetate 4a (Conv 50% and E > >200).

Chiral Bicyclic Imidazole-Catalyzed Direct Enantioselective C -Acetylation of Indolones

Chiral Bicyclic Imidazole-Catalyzed Direct Enantioselective <i>C</i> -Acetylation of Indolones

Base-induced Sommelet–Hauser rearrangement of N-(pyridinylmethyl) tetraalkylammonium salts

The base-induced Sommelet–Hauser (S–H) rearrangement of various types of N-(pyridinylmethyl) tetraalkylammonium salts 2 to produce N,N-dialkyl-α-pyridinylamino acid esters 4 was investigated. For example, a treatment of N-(2-pyridinylmethyl) glycine tert-butyl ester-derived tetraalkylammonium salt 2a with 1.2 equivalents of potassium tert-butoxide in THF at −40 °C gave the corresponding S–H product, tert-butyl 2-(dimethylamino)-2-(2-methylpyridin-3-yl)acetate (4a), in 93% yield. Our method is an efficient C–H functionalization of pyridines under simple and mild conditions.

A combined experimental and theoretical study of alkyl 2-(3-benzoyl-4‑hydroxy-1,1-dioxido-2H-benzo[e][1,2]thiazin-2-yl)acetates: Synthesis, X-ray crystallography and DFT

Benzothiazine derivatives belongs to an important class of organic compounds with a wide range of application in the field of biotechnology and medicinal chemistry, and many of its derivatives have been considered in drug discovery. A series of three alkyl 2-(3-benzoyl-4‑hydroxy-1,1-dioxido-2H-benzo[e][1,2]thiazin-2-yl)acetates (3a–c) were synthesized from the sulfonimidamides through multistep reactions. The molecular geometry of these compounds has been investigated with the help of X-ray crystallography and quantum mechanical calculations. The molecular structural optimization and structural properties were calculated using the Density Functional Theory method and B3LYP hybrid functional with 6–311+G* basis set. Non-covalent interactions studies, energetics and reactivity properties of 3a-c compounds have been explored through local and global reactivity descriptors, UV-Visible spectral analysis and molecular electrostatic potential illustrations. It is found that the compound 3b is more reactive than others because of its lowest frontier molecular orbital energy gap (ΔE=3.46 eV) and low chemical hardness (η=0.23eV) than others. Furthermore, the investigations of Non-linear optical properties and thermodynamic parameters have also been carried out which shows that these compounds can be used as a non-linear optical material in the field of telecommunication and information technologies.

Practical access to (S)-heterocyclic aromatic acetates via CAL-B/Na2CO3-deacylation and Mitsunobu reaction protocol

Herein, we report the preparation of enantiomerically pure forms of 2,3-dihydrobenzofuran-3-ol (1), chroman-4-ol (2), thiochroman-4-ol (3), 1-(furan-2-yl) ethanol (5) and 1-(thiophen-2-yl) ethanol (6), through a kinetic resolution catalysed by Candida antarctica lipase B/Na2CO3 hydrolysis sequence in organic media. The (R)-furnished alcohols and the (S)-remained acetates are recovered enantiopures (ee >99%, E ≫ 200, Conv = 50%). Those ideal enzymatic kinetic resolution (EKRs) are well incorporated to the Mitsunobu inversion protocol in a one pot procedure to give (S)-heterocyclic acetates (1a–3a) in good to high enantiomeric excess (88%–92% ee). Whilst, the (S)-heteroaromatic acetates (5a and 6a) are given with moderate enantiomeric excess (51%–62% ee). All the (S)-acetates are given in good isolated chemical yields (>80%) allowing to overcome the maximum of 50% yield which could be usually reached in a regular kinetic resolution processes.

Utility of pyrrole‐2‐thioacetohydrazide in synthesis of new heterocyclic compounds with promising antimicrobial activities and molecular docking studies

AbstractOne‐pot synthetic method for [(3‐cyano‐5‐phenyl‐1H‐pyrrol‐2‐yl)sulfanyl]acetic acids 3a,b with excellent yield have been accomplished via a tetrabutylammonium bromide (TBAB) catalyzed reaction of mercaptoacetic acid with 2‐(2‐oxo‐2‐arylethyl) malononitrile under phase transfer catalysis conditions (PTC). The coupling of methyl [(3‐cyano‐5‐phenyl‐1H‐pyrrol‐2‐yl)sulfanyl] acetate 4a,b with hydrazine gave the corresponding 2‐[(3‐cyano‐5‐aryl‐1H‐pyrrol‐2yl)thio] acetohydrazides 5a,b, which reacted with glucose, acetylacetone, carbon disulfide, phenyl isothiocyanate, chloroacetyl chloride or benzaldehyde, to afford the compounds 6a,b–11a,b, respectively ranged from satisfactory to excellent yields. In vitro antibacterial and antifungal activities were assessed with good results. Furthermore, molecular docking experiments were done for the most active compounds against the E. coli MurB enzyme in order to determine the mechanism of their antibacterial activity and showed good binding interactions.

Two Approaches for CAL-B-Catalyzed Enantioselective Deacylation of a Set of α-Phenyl Ethyl Esters: Organic Solvent with Sodium Carbonate and Micro-aqueous Medium

Herein, we report an efficient enantioselective cleavage of the acyl- moiety of a set of α- phenyl ethyl esters with different chain-lengths catalyzed by lipase B from Candida antarctica (CAL-B) by comparing two reactional approaches: anhydrous media with sodium carbonates and micro-aqueous medium. The deacylation is performed in organic solvent, in the presence of Na2CO3 in the first case, and by addition of a drop of phosphate buffer solution pH 7 in the second. The results show the high efficiency of the deacylation in the presence of the sodium carbonate for the enzymatic resolution of all the esters and that in term of reactivity (31% ≤ conv ≤ 50%) and selectivity (E > 200). While, during the hydrolysis in micro-aqueous media, the conversion is strongly affected by the length of the acyl-chain side, the conversion decreases from conv = 50% with the 1-phenylethyl acetate 1a to conv = 19% with 1-phenyethyl dodecanoate 6a, and this, even if the selectivity remains high (E > 89). In both conditions, the lipase CAL-B shows a high enantioselectivities in favor of (R)-1-phenyl ethanol enantiomer (conv > 45%, E > 200) but the reactivity is modulated by the form and the size of the acyl-chain side.Graphic Abstract

Antioxidant Activity and Chemical Constituents from Stem Bark of Ficus abutilifolia. Miq (Moraceae)

Aims: The present study was conducted to determine the antioxidant activity and chemical components of Ficus abutilifolia. Miq. (Moraceae).&#x0D; Place and Duration of the Study: The study were performed at Department of chemistry, University of Ngaoundere, Cameroon, between July 2017 and September 2018.&#x0D; Methodology: Phytochemical study was carried out on all extracts of stem barks. Besides, the total phenols contents (TPC) using the Folin-Ciocalteu and the antioxidant activities using DPPH and FRAP methods were also evaluated. The isolation of compounds from the EtOAc extract was done using column and thin layer chromatographic techniques on silica gel. The structures of isolated constituents were elucidated using mass spectrometry, 1D and 2D-NMR techniques.&#x0D; Results: Phytochemical screening revealed that all the compounds tested were found to be present in the acetone extract; the hexane extract was the poorest in compounds. Acetone extract, DCM/MeOH (1:1) and MeOH extracts were found to be rich in phenols with TPC respectively (239. 849 ± 0.969), (232.676 ± 0.404) and (109.654 ± 0.724) mg EAG/100g EX. Except the n-hexane extract, all the others exhibit antioxidant activities, acetone extract being the most effective with an inhibitory concentration 50 (IC50) of (0.038 ± 0.002) mg/mL for the DPPH antiradical scavenging activity and (0,021 ± 0,002) mg/mL for FRAP. A new fatty acid named Pentacosyl henicosanoate (2) along with six known compounds Octatriacontane (1), β–sitosterol (3), a mixture of Lupeol acetate (4a), α-amyrin acetate (4b), β-amyrin acetate (4c) and Daucosterol (5) were isolated from the column chromatography of the ethyl acetate extract. Daucosterol (5) exhibited antiradical activity with an IC50 of (13.005 ± 0.005) mg/mL. Only Daucosterol (5) has exhibited antiradical activity with an IC50 of (13.005 ± 0.005) mg/mL among the isolated compounds.&#x0D; Conclusion: This study provides scientific evidence and support for the traditional uses of F. abutilifolia stem barks in the treatment of diseases associated with oxidative stress.

Application of the redox system of Nocardia corallina B-276 in the enantioselective biotransformation of ketones and alcohols

The aim of this research was to evaluate the redox system of Nocardia corallina B-276 in the biotransformation of 1-phenyl-1-propanone (1a), 2-hydroxy-1-phenylethanone (2a) and methyl (2-chlorophenyl)(oxo)acetate (3a) into 1-phenylpropan-1-ol (1b), 1-phenyl-1,2-ethanediol (2b) and methyl (2-chlorophenyl)(hydroxy)acetate (3b). The biomass of N. corallina was obtained in a liquid medium with an initial pH of 8.50, but the pH changed during the 96 h of the culture media, the final pH was between 4.74 and 7.62. The N. corallina biomass biocatalyzed the enantioselective reduction of 1a?3a to the corresponding alcohols. Whereas, during the process of oxidation of the rac-alcohols 1b?3b, 1b was oxidized in enantioselective way, the oxidation of 2b was not selective, but 3b was biotransformed mainly to (R)-3b. These results are indicative that N. corallina produced reductases and oxidases, whereby the biocatalytic activity was influenced by the final pH of the culture media, the reaction time and structure of the substrate.

Acetylation of cedrelone increases its cytotoxic activity and reverts the malignant phenotype of breast cancer cells in 3D culture

Cedrelone is a limonoid isolated from the plant Trichilia catigua (Meliaceae). Previous studies have demonstrated that cedrelone (1) has several damaging effects on triple negative breast tumor (TNBC) cell line MDA-MB-231. In this work we investigated two new derivatives of cedrelone, the acetate (1a) and the mesylate (1b), to examine whether their effects are improved in comparison to the lead molecule. Cedrelone acetate (1a) was the most cytotoxic compound on TNBC cells and was chosen for additional analyses in traditional two-dimensional (2D) monolayer cultures and three-dimensional (3D) assays. In 2D, 1a induced cell cycle arrest, apoptosis and inhibited essential steps of the metastasis process of the MDA-MB-231 cells, in vitro. Moreover, 1a was able to revert the malignant phenotype of the T4-2 cells in 3D. These effects were concomitant with the downregulation of EGFR, β1-integrin and phospho-Akt, which could have resulted in a decrease of NFκB levels and MMP9 activity. These results suggest that 1a could be used as an important model for the design of a new drug to be applied in cancer treatment and be further studied in vivo for its antitumor and antimetastatic effects.

SYNTHESIS, CHARACTERIZATION AND ANTIMICROBIAL EVALUATION OF SOME HITHERTO UNKNOWN 4-OXO-THIAZOLES AND THIAZOLO [3, 2-A] PYRIDINES

2-(4-Oxothiazolidin-2-ylidene) acetonitrile and ethyl -2-(4-oxothiazolidin-2-ylidene) acetate (1a, b), were condensed with anthralaldehyde (1:1 molar ratio) and gave 4, 5-dihydro-4-oxothiazole derivatives (2a, b). Refluxing of 2-(Antharacene-9-yl-methylene) malononitrile in acetic acid with thioglycollic acid gave (3). 4-Thiazolidinones containing bis aryl methylidine moieties (4a-c) and (5a, b) were produced via condensation of either (2a) or (3) with different aromatic aldehydes (1:1 molar ratio). Heating of (2a) with α-substituted cin- namonitriles gave the expected substituted thiazolo [3, 2-a] pyridines (6a-d), (8) and (10a-c). The synthesized compounds have been screened for their antimicrobial activities against some selected species of Gram-positive (G+). Gram-negative (G-) bacteria and 3 different types of fungi. They were found to be more active against Gram positive than Gram negative bacteria.

Regio- and Enantioselective Iridium-Catalyzed Amination of Racemic Branched Alkyl-Substituted Allylic Acetates with Primary and Secondary Aromatic and Heteroaromatic Amines.

The air- and water-stable π-allyliridium C,O-benzoate modified by ( S)-tol-BINAP, ( S)-Ir-II, catalyzes highly regio- and enantioselective Tsuji-Trost-type aminations of racemic branched alkyl-substituted allylic acetates using primary or secondary (hetero)aromatic amines. Specifically, in the presence of ( S)-Ir-II (5 mol%) in DME solvent at 60-70 °C, α-methyl allyl acetate 1a (100 mol%) reacts with primary (hetero)aromatic amines 2a-2l (200 mol%) or secondary (hetero)aromatic amines 3a-3l (200 mol%) to form the branched products of allylic amination 4a-4l and 5a-5l, respectively, as single regioisomers in good to excellent yield with uniformly high levels of enantioselectivity. As illustrated by the conversion of heteroaromatic amine 3m to adducts 6a-6g, excellent levels of regio- and enantioselectivity are retained across diverse branched allylic acetates bearing normal alkyl or secondary alkyl substituents. For reactants 3n-3p, which incorporate both primary and secondary aryl amine moieties, regio- and enantioselective amination occurs with complete site-selectivity to furnish adducts 7a-7c. Mechanistic studies involving amination of the enantiomerically enriched, deuterium-labeled acetate 1h corroborate C-N bond formation via outer-sphere addition.

Paramagnetic Chromium(II) Complexes and Chromium(IV) Nitrides with Bulky Alkylcyclopentadienyl Ligands

Easily available chromium(II) acetate was used for an entry into chromium chemistry: sodium tetraisopropylcyclopentadienide (Na4Cp), sodium 1,2,4‐tri(tert‐butyl)cyclopentadienide (NaCp′′′), or lithium pentaisopropylcyclopentadienide (Li5Cp) convert the acetate to the acetate‐bridged dimers [4CpCr(µ‐OOCCH3)]2 (1a), [Cp′′′Cr(µ‐OOCCH3)]2 (1b), or [5CpCr(µ‐OOCCH3)]2 (1c) in yields well above 70 %. These acetates could be converted into the halide‐bridged dimers [4CpCr(µ‐Cl)]2 (2a), [4CpCr(µ‐Br)]2 (3a), [Cp′′′Cr(µ‐Br)]2 (3b), or [5CpCr(µ‐Br)]2 (3c), [4CpCr(µ‐I)]2 (4a), or [Cp′′′Cr(µ‐I)]2 (4b) with the corresponding trimethylsilyl halides in nearly quantitative yield. With bis(trimethylsilyl)sulfate the acetate 1a gave crude bis(tetraisopropylcyclopentadienylchromium)sulfate (5a). From the bromide 3b and sodium bis(trimethylsilyl)amide the mononuclear chromium(II) silylamide [Cp′′′CrN(SiMe3)2(THF)] (7b) was obtained as a tetrahydrofuran adduct. Upon reaction with sodium azide, the iodide 4a afforded the tetranuclear chromium(IV) nitride cubane [(4CpCr)3(µ3‐N)4CrOH] (8a) after extraction with heptane containing traces of water. The analogous chromium nitride derivative [(Cp′′′Cr)3(µ3‐N)4CrBr] (9b) was obtained from the bromide 3b and sodium azide.

Medium effect on the α-effect for nucleophilic substitution reactions of p-nitrophenyl acetate with benzohydroxamates and m-chlorophenoxide in DMSO–H2O mixtures as contrasts with MeCN–H2O mixtures: comparing two very different polar aprotic solvent components

A kinetic study is reported on nucleophilic substitution reactions of p-nitrophenyl acetate (1a) with three α-effect nucleophiles, benzohydroxamate (BHA–), p-methylbenzohydroxamate (MBHA–), and p-methyl-N-methylbenzohydroxamate (M2BHA–), and a reference nucleophile, m-chlorophenoxide (m-ClPhO–), in DMSO–H2O mixtures of varying compositions at 25.0 ± 0.1 °C. Second-order rate constants for the reactions with BHA– and MBHA– decrease upon addition of DMSO to the reaction medium up to 60 mol % DMSO and then increase thereafter only a little. In contrast, M2BHA– and m-ClPhO– become much more reactive as the DMSO content in the medium increases. Such contrasting medium effects on reactivity are consistent with the report that hydroxamic acids behave as OH acids in H2O but as NH acids in dipolar aprotic solvents (e.g., DMSO and MeCN). It has been concluded that BHA– and MBHA– form an equilibrium of a reactive form I with less reactive species II in DMSO–H2O mixtures and the position of the equilibrium is dependent on solvent compositions. BHA– and MBHA– exhibit the α-effect in H2O but not in in 90 mol % DMSO. In contrast, the α-effect yielded by M2BHA– increases steeply up to 70 mol % DMSO and then levels off thereafter.

Application of Lecitase® Ultra-Catalyzed Hydrolysis to the Kinetic Resolution of (E)-4-phenylbut-3-en-2-yl Esters

The possibility of using Lecitase® Ultra as a novel alternative biocatalyst for the kinetic resolution of model racemic allyl esters of (E)-4-phenylbut-3-en-3-ol: Acetate (4a) and propionate (4b) through their enantioselective hydrolysis was investigated. Reaction afforded (+)-(R)-alcohol (3) and unreacted (−)-(S)-ester (4a or 4b). Hydrolysis of propionate 4b proceeded with higher enantioselectivity than acetate 4a. (R)-Alcohol (3) with highest enantiomeric excess (93–99%) was obtained at 20–30 °C by hydrolysis of propionate 4b, while the highest optical purity of unreacted substrate was observed for (S)-acetate 4a (ee = 34–56%). The highest enantioselectivity was found for the hydrolysis of propionate 4b catalyzed at 30 °C (E = 38). Reaction carried out at 40 °C significantly lowered enantiomeric excess of produced alcohol 3 and enantioselectivity in resolution. Lecitase® Ultra catalyzed the enantioselective hydrolysis of allyl esters 4a,b according to Kazlauskas’ rule to produce (R)-alcohol 3 and can find application as a novel biocatalyst in the processes of kinetic resolution of racemic allyl esters.

Werner transition‐metal complex (WTMC)‐mediated mild and efficient chemo‐selective acylation of phenols and anilines under solvent‐free condition

Werner‐type transition‐metal complexes (WTMC) such as [Co(NH3)5Cl]Cl2, Cu[(NH3)4]SO4, Mn(acac)3, Ni[(NH3)6]Cl2, Ni[(en)3]S2O3, and Hg[Co(SCN)4] efficiently promote the chemoselective acetylation of phenols and anilines under solvent‐free condition. The results of this study clearly shows that the optimal condition for the acetylation of anilines/phenols (1 mmol) (2a–r) with acetic anhydride (1.2 mmol) in the presence of WTMC (1 mmol) and two drops of H3PO4 on heating for 10 min under solvent‐free condition gives the corresponding acetanilides/phenyl acetate (3a–r) in good to excellent yield. Furthermore, the method is simple, efficient, chemoselective, and eco‐friendly under solvent‐free condition for the acetylation of anilines and phenols promoted by WTMC by using acetic anhydrate as the acetylating agent. The simple preparation of the catalyst, easy procedure of the acetylation reaction, and simple work‐up indicate the importance of WTMC for such reactions.

Design, Synthesis, and Biological Evaluation of the Sex Pheromone of the Asian Corn Borer, Ostrinia furnacalis (Guenée)

A convenient total synthesis of (Z)-12-tetradecenyl acetate (1a) and (E)-12-tetradecenyl acetate (1b), which are the sex pheromones of Ostrinia furnacalis (Guenée), has been achieved. The target mixture molecules, of a cis-to-trans-isomer ratio of 27 to 73, were synthesized in 40% overall yield and through [13C + 1C] synthetic strategy in five steps from commercially available and cheap industrial brassylic acid as key starting material. The electroantennogram (EAG) responses of synthetic sex pheromone to ACB male moths were conducted. The results showed that the target mixture molecules were found to have a good activity and displayed significantly stronger EAG responses ranging from 10 to 1000 μg, and the optimized stimulating dosage of the activity of synthetic sex pheromone to ACB males is 10 μg. Compared with the existing routes, this synthetic approach is operationally simple, good-yielding, and cost-effective, which could serve as a basis for developing the techniques of sex pheromone mass trapping or mating disruption and providing an environmentally benign method to control ACB pests.

Effects of base strength on the copper-catalyzed cycloisomerization of propargylic acetates to form indolizines: A DFT study

Our calculations find that the base strength is the primary factor that controls the catalytic capability of cocatalysts CH3CN, Propargylic acetates (1a) and Et3N. In the proton-transfer process, the trend of catalytic activity increases in the order: Et3N > 1a > CH3CN, which matches well with the enhanced trend of base strength (Et3N > 1a > CH3CN). Et3N is the most appropriate for the present Cu-catalyzed cycloisomerization of propargylic acetates, which is in agreement with the experimental phenomena. Besides, our calculations give a reasonable explanation for the effects of terminal substituents (H- vs. Ph-) of alkyne on the catalytic reaction.