Cycloaddition Of Terminal Alkynes Research Articles

Synthesis of thiazolidine-2,4-dione tethered 1,2,3-triazoles as α-amylase inhibitors: In vitro approach coupled with QSAR, molecular docking, molecular dynamics and ADMET studies

A new series of thiazolidine-2,4-dione tethered 1,2,3-triazole derivatives were designed, synthesized and screened for their α-amylase inhibitory potential employing in vitro and in silico approaches. The target compounds were synthesized with the help of Cu (I) catalyzed [3 + 2] cycloaddition of terminal alkyne with numerous azides, followed by unambiguously characterizing the structure by employing various spectroscopic approaches. The synthesized derivatives were assessed for their in vitro α-amylase inhibition and it was found that thiazolidine-2,4-dione derivatives 6e, 6j, 6o, 6u and 6x exhibited comparable inhibition with the standard drug acarbose. The compound 6e with a 7-chloroquinolinyl substituent on the triazole ring exhibited significant inhibition potential with IC50 value of 0.040 μmol mL−1 whereas compound 6c (IC50 = 0.099 μmol mL−1) and 6h (IC50 = 0.098 μmol mL−1) were poor inhibitors. QSAR studies revealed the positively correlating descriptors that aid in the design of novel compounds. Molecular docking was performed to investigate the binding interactions with the active site of the biological receptor and the stability of the complex over a period of 100 ns was examined using molecular dynamics studies. The physiochemical properties and drug-likeliness behavior of the potent derivatives were investigated by carrying out the ADMET studies.

Mechanistic Investigation on the Regioselectivity of Electrochemical Co(II)-Catalyzed [2 + 2 + 2] Cycloaddition of Terminal Acetylenes.

In this paper, the regioselectivity of electrochemical Co(II)-catalyzed [2 + 2 + 2] cycloaddition of terminal alkynes was investigated using density functional theory. We explored in detail the energy profiles for both 1,2,4- and 1,3,5-regioselectivity pathways and revealed the origin of the regioselectivity. Two kinds of conformational isomers derived from the different coordination modes of alkynes with cobaltacyclopentadiene have been found, which were formed through electrochemically mediated redox processes. The regioselectivity of the reaction depends on the two coordination modes. When the Co(II) center attacks α-C of the third alkyne, while β2-C in cyclopentadiene bonds to β-C of the alkyne, the reaction favors the formation of 1,2,4-products. In contrast, when the Co(II) center connects to β-C of the alkyne, it forms only the 1,3,5-products via [4 + 2] cycloaddition because of the steric repulsion between the bulky ligand on Co(II) and the phenyl group in the alkyne.

Copper and Silver Catalysis in the (3 + 2) Cycloaddition of Neutral Three-Atom Components with Terminal Alkynes.

The introduction of the copper-catalyzed azide-alkyne coupling (CuAAC) to 1,3-dipolar cycloadditions was pivotal to their popularization in synthetic chemistry and to their application to multiple other domains of science. The reaction rate enhancement observed when coinage metal acetylide intermediates are involved in the cyclization process greatly expanded the structural and conditional range in which (3 + 2) cycloadditions may take place with terminal alkynes. Herein, we report that comparable rate enhancements, in nature and level, are induced by copper and silver catalysts in the intramolecular (3 + 2) cycloaddition of terminal alkynes with "neutral" three-atom components (TACs), specifically alkynyl sulfides. Through careful observations amidst reaction optimization, experimental, and DFT mechanistic studies, a pathway involving a proton-coupled cyclometallation key step is proposed. The sets of catalytic conditions that have been developed allow us to overcome several scope limitations previously presented by the thermally promoted (3 + 2) cycloaddition of "neutral" TACs, thus expanding their synthetic and applicative potential.

A Copper‐Catalyzed [5+1] Cycloaddition of Terminal Alkynes with Diazo Esters through a Tandem 1,5‐H‐Shift Cyclization

Comprehensive SummaryA copper‐catalyzed [5+1] cycloaddition reaction of terminal alkynes with diazo esters for the rapid construction of protected naphthalen‐1(2H)‐one derivatives in moderate to good yields has been disclosed along with good functional group compatibility and a broad substrate scope. The mechanistic investigations reveal that this tandem cyclization process proceeds through a Cu(I)‐catalyzed coupling of terminal alkyne with diazoacetate, a 1,5‐H shift process and a thermally induced pericyclic reaction via an allene intermediate. The synthetic utility and the further transformations of the obtained cycloadduct to naphthalenone, naphthol and dihydronaphthol have been also presented in this paper.

MOF-Derived Cu@N-C Catalyst for 1,3-Dipolar Cycloaddition Reaction.

Cu(im)2-derived Cu@N-C composites were used for the first time as efficient heterogeneous catalysts for one-pot 1,3-dipolar cycloaddition of terminal alkynes, aryl halides, and sodium azide to preparation of 1,4-disubstituted 1,2,3-triazoles with broad substrate scope and high yields. The catalyst can be easily reused without the changes of structure and morphology, and the heterogeneity nature was confirmed from the catalyst recyclability and metal leaching test.

Ferrocene conjugates linked by 1,2,3‐triazole and their Zn(II) and Cu(II) complexes: Synthesis, characterization and biological activity

AbstractFerrocene derivatives with mono‐ (8a–c) and bis‐1,2,3‐triazolyl (9 and 10a–13c) chelating groups were synthesized by regioselective copper(I)‐catalysed 1,3‐dipolar cycloaddition of terminal alkynes with ferrocene azides. Metal complexes of the ligands were prepared with Cu(II) and Zn(II) salts. Crystal structures of ligands 9 and 11a were determined, as well as the structures of complexes [Cu(8a)2](CF3SO3)2 (8aCu) and [Cu(8c)2(CH3OH)2](BF4)2 (8cCu). In addition to NMR and UV–Vis spectroscopy, the metal complexes were characterized by cyclic voltammetry. The cytotoxic effect of ferrocene conjugates and their Zn(II) and Cu(II) complexes was explored, and cell cycle analysis was performed. The complex [Cu(8c)2](CF3SO3)2 showed the most prominent and selective cytotoxicity on cervical carcinoma (HeLa), ovarian cancer (MES‐OV), non‐small cell lung cancer (A549) and breast carcinoma (MDA‐MB‐231) cells. This complex increased cell population in the S and G2/M phase of the cell cycle, which was accompanied by an increase of the cells present in the sub‐G0/G1 fraction.

Fluorine-18 click radiosynthesis and microPET/CT evaluation of a small peptide-a potential PET probe for carbonic anhydrase IX.

Carbonic anhydrase IX (CA IX) is the first carbonic anhydrase found to be associated with cancer that is over-expressed in a variety of human solid tumors. As a surrogate marker for hypoxia, the expression of CA IX is strongly upregulated in hypoxic tumors by hypoxia and hypoxia-inducible factor 1a (HIF-1a). In our pursuit of a CA IX-specific PET probe, we designed and synthesized a peptide-based CA IX imaging probe by the efficient click reaction of 1,3-dipolar cycloaddition of terminal alkynes and organic azides. The probe 18F-CA IX-P1-4-10 was obtained with a radiochemical yield of 35-45% (n = 5) and radiochemical purity of >99% in 70-80 min (HPLC purification time included). 18F-CA IX-P1-4-10 had good stability in phosphate buffered saline (PBS), but about 51% peptide degradation was detected in new-born calf serum (NBCS) after incubation. Preliminary microPET/CT experiments demonstrated a specific uptake of 18F-CA IX-P1-4-10 in HT29 tumor and the uptake of 18F-CA IX-P1-4-10 was blocked by peptide CA IX-P1-4-10-Yne pretreatment. Immunohistochemical staining and western blotting studies confirmed the HT29 tumor was CA IX-positive which further proved tumor accumulation of 18F-CA IX-P1-4-10 was correlated with CA IX expression. The results suggest that 18F-CA IX-P1-4-10 is a promising PET tracer for the specific imaging of CA IX-expressing tumors at the molecular level.

Gold-Catalyzed Enantioselective [2+2] Cyclo-addition of Terminal Alkynes and Alkenes

Key words gold catalysis - cycloaddition - alkynes - alkenes - cyclobutenes - total synthesis

Enantioselective Synthesis of Cyclobutenes by Intermolecular [2+2] Cycloaddition with Non-C2 Symmetric Digold Catalysts.

The enantioselective intermolecular gold(I)-catalyzed [2+2] cycloaddition of terminal alkynes and alkenes has been achieved using non-C2-chiral Josiphos digold(I) complexes as catalysts, by the formation of the monocationic complex. This new approach has been applied to the enantioselective total synthesis of rumphellaone A.

DFT Study on Rhodium-Catalyzed Intermolecular [2 + 2] Cycloaddition of Terminal Alkynes with Electron-Deficient Alkenes

Density functional theory (DFT) calculations with the B3LYP functionals elucidated the reactivity, selectivity, and mechanisms of a rhodium-catalyzed intermolecular [2 + 2] cycloaddition of terminal alkynes with electron-deficient alkenes. The most plausible reaction pathway was discussed as three distinct processes in full catalytic cycles, including (1) substrate exchange, (2) nucleophilic addition and cyclization, and (3) separation of product and recycling of catalyst; the formal [2 + 2] cycloaddition indeed proceeded through a rate-determining and stepwise addition–cyclization process. We then compared the outer-sphere and inner-sphere mechanisms for the formation of cyclobutene intermediates and reported that the former pathway is more accessible kinetically and thus more competitive, being contrary to the proposed mechanism for some nickel-catalyzed cycloaddition reactions in the literature. Furthermore, the substituent effect has been investigated using various alkenes CH2═CHR (R = COOMe, CN, H, C...

Selective Intermolecular [2+2+2] Cycloaddition of Terminal Alkynes and Alkenes by NbCl5 as a Catalyst Precursor

Abstract NbCl5 serves as an efficient catalyst for the intermolecular [2+2+2] cycloaddition of alkynes and alkenes to afford 1,3-cyclohexadienes. A convenient system has been developed using excess alkene, which enables the reaction to proceed without using low-valent niobium reagents or any reductants. This catalytic system affords 1,3-cyclohexadiene with high chemo- and regioselectivity, in contrast to a previously reported system involving NbCl3(DME) as a low-valent niobium catalyst.

ChemInform Abstract: Rhodium‐Catalyzed [3 + 2 + 2] and [2 + 2 + 2] Cycloadditions of Two Alkynes with Cyclopropylideneacetamides.

AbstractA cationic Rh(I)/(S)‐BINAP complex catalyzes the enantioselective [2+2+2]‐cycloaddition of terminal alkynes, acetylenedicarboxylates and cyclopropylideneacetamides to furnish spiro‐cyclohexadiene derivatives without cleavage of the cyclopropane ring.

ChemInform Abstract: Niobium Complexes in Organic Transformations: From Stoichiometric Reactions to Catalytic [2 + 2 + 2] Cycloaddition Reactions

AbstractReview: [57 refs.

Selective Oligomerization and [2 + 2 + 2] Cycloaddition of Terminal Alkynes from Simple Actinide Precatalysts

A catalyzed conversion of terminal alkynes into dimers, trimers, and trisubstituted benzenes has been developed using the actinide amides U[N(SiMe3)2]3 (1) and [(Me3Si)2N]2An[κ2-(N,C)-CH2Si(CH3)N(SiMe3)] (An = U (2), Th (3)) as precatalysts. These complexes allow for preferential product formation according to the identity of the metal and the catalyst loading. While these complexes are known as valuable precursors for the preparation of various actinide complexes, this is the first demonstration of their use as catalysts for C–C bond forming reactions. At high uranium catalyst loading, the cycloaddition of the terminal alkyne is generally preferred, whereas at low loadings, linear oligomerization to form enynes is favored. The thorium metallacycle produces only organic enynes, suggesting the importance of the ability of uranium to form stabilizing interactions with arenes and related π-electron-containing intermediates. Kinetic, spectroscopic, and mechanistic data that inform the nature of the activation...

Rhodium‐Catalyzed [3+2+2] and [2+2+2] Cycloadditions of Two Alkynes with Cyclopropylideneacetamides

AbstractIt has been established that a cationic rhodium(I)/H8‐binap complex catalyzes the [3+2+2] cycloaddition of 1,6‐diynes with cyclopropylideneacetamides to produce cycloheptadiene derivatives through cleavage of cyclopropane rings. In contrast, a cationic rhodium(I)/(S)‐binap complex catalyzes the enantioselective [2+2+2] cycloaddition of terminal alkynes, acetylenedicarboxylates, and cyclopropylideneacetamides to produce spiro‐cyclohexadiene derivatives which retain the cyclopropane rings.

Rhodium-Catalyzed [3+2+2] and [2+2+2] Cycloadditions of Two Alkynes with Cyclopropylideneacetamides.

It has been established that a cationic rhodium(I)/H8 -binap complex catalyzes the [3+2+2] cycloaddition of 1,6-diynes with cyclopropylideneacetamides to produce cycloheptadiene derivatives through cleavage of cyclopropane rings. In contrast, a cationic rhodium(I)/(S)-binap complex catalyzes the enantioselective [2+2+2] cycloaddition of terminal alkynes, acetylenedicarboxylates, and cyclopropylideneacetamides to produce spiro-cyclohexadiene derivatives which retain the cyclopropane rings.

Niobium Complexes in Organic Transformations: From Stoichiometric Reactions to Catalytic [2+2+2] Cycloaddition Reactions

AbstractNiobium complexes in organic reactions have received a lot of attention in recent years. Niobium is one of the early transition metals, which possess unique reactivity distinct from that of other transition metals. This review focuses mainly on stoichiometric reactions and catalytic reactions involving niobium complexes. In particular, recent results relating to NbV‐mediated or NbIII‐catalyzed [2+2+2] cycloaddition of unsaturated compounds (alkyne, alkenes, nitriles, and isocyanates) are mainly presented in this review. In one example of a set of catalytic reactions involving a low‐valent niobium species, the reaction between NbCl5 and tris(trimethylsilyl)silane generated a low‐valent niobium(III) species, and this promoted [2+2+2] cycloaddition of terminal alkynes and olefins to provide cyclohexa‐1,3‐dienes. In addition, the use of low‐valent niobium(III) species in stoichiometric reactions has also been reported. Many of these reactions are carried out by formation of Nb–alkyne complexes through reactions between low‐valent niobium(III) and internal alkynes. Some examples of the use of Nb complexes as Lewis acids have also been reported. In these reactions, the valence of the Nb complexes is V.

Facile Synthesis of 2,5-Disubstituted Thiazoles from Terminal Alkynes, Sulfonyl Azides, and Thionoesters

A sequential procedure for the synthesis of 2,5-disubstituted thiazoles from terminal alkynes, sulfonyl azides, and thionoesters is reported. A copper(I)-catalyzed 1,3-dipolar cycloaddition of terminal alkynes with sulfonyl azides affords 1-sulfonyl-1,2,3-triazoles, which then react with thionoesters in the presence of a rhodium(II) catalyst. The resulting 3-sulfonyl-4-thiazolines subsequently aromatize into the corresponding 2,5-disubstituted thiazoles by elimination of the sulfonyl group.

ChemInform Abstract: Synthesis and NMR Analysis of 1,4‐Disubstituted 1,2,3‐Triazoles Tethered to Pyridine, Pyrimidine, and Pyrazine Rings.

AbstractCopper catalyzed 1,3‐dipolar cycloaddition of terminal alkynes and aromatic or benzylic azides containing different six‐membered aromatic N‐heteroaryl substituents is examined to yield a variety of 1,2,3‐triazoles with the expected regioselectivity.

ChemInform Abstract: Silver‐Catalyzed Cyclization of 2‐Pyridyl Alkynyl Carbinols with Isocyanides: Divergent Synthesis of Indolizines and Pyrroles.

Divergent syntheses of indolizines and 2,4-disubstituted pyrroles by the silver-catalyzed cyclization of 2-pyridyl alkynyl carbinols with isocyanides are reported. These methods provide an effective route to highly functionalized indolizines and 2,4-disubstituted pyrroles in good to excellent yields. The 2,4-disubstituted pyrroles are synthesized by an unprecedented regioselective [3+2] cycloaddition of terminal alkynes with isocyanides.