Aliphatic Alkynes Research Articles

Ligand-Free Palladium-Mediated Site-Specific Protein Labeling Inside Gram-Negative Bacterial Pathogens

Palladium, a key transition metal in advancing modern organic synthesis, mediates diverse chemical conversions including many carbon-carbon bond formation reactions between organic compounds. However, expanding palladium chemistry for conjugation of biomolecules such as proteins, particularly within their native cellular context, is still in its infancy. Here we report the site-specific protein labeling inside pathogenic Gram-negative bacterial cells via a ligand-free palladium-mediated cross-coupling reaction. Two rationally designed pyrrolysine analogues bearing an aliphatic alkyne or an iodophenyl handle were first encoded in different enteric bacteria, which offered two facial handles for palladium-mediated Sonogashira coupling reaction on proteins within these pathogens. A GFP-based bioorthogonal reaction screening system was then developed, allowing evaluation of both the efficiency and the biocompatibilty of various palladium reagents in promoting protein-small molecule conjugation. The identified simple compound-Pd(NO3)2 exhibited high efficiency and biocompatibility for site-specific labeling of proteins in vitro and inside living E. coli cells. This Pd-mediated protein coupling method was further utilized to label and visualize a Type-III Secretion (T3S) toxin-OspF in Shigella cells. Our strategy may be generally applicable for imaging and tracking various virulence proteins within Gram-negative bacterial pathogens.

ChemInform Abstract: A Domino Desulfitative Coupling/Acylation/Hydration Process Cocatalyzed by Copper(I) and Palladium(II): Synthesis of Highly Substituted and Functionalized Pyrimidines.

AbstractA series of substituted pyrimidines is synthesized by the present new multicomponent reaction of pyrimidinethiones, aromatic and aliphatic alkynes (II), and a copper(I) carboxylate under modified Liebeskind—Srogl conditions.

Sky-Blue Luminescent AuI–AgI Alkynyl-Phosphine Clusters

Treatment of the (AuC2R)n acetylides with phosphine ligand 1,4-bis(diphenylphosphino)butane (PbuP) and Ag(+) ions results in self-assembly of the heterobimetallic clusters of three structural types depending on the nature of the alkynyl group. The hexadecanuclear complex [Au12Ag4(C2R)12(PbuP)6](4+) (1) is formed for R = Ph, and the octanuclear species [Au6Ag2(C2R)6(PbuP)3](2+) adopting two structural arrangements in the solid state were found for the aliphatic alkynes (R = Bu(t) (2), 2-propanolyl (3), 1-cyclohexanolyl (4), diphenylmethanolyl (5), 2-borneolyl (6)). The structures of the compounds 1-4 and 6 were determined by single crystal X-ray diffraction analysis. The NMR spectroscopic studies revealed complicated dynamic behavior of 1-3 in solution. In particular, complexes 2 and 3 undergo reversible transformation, which involves slow interconversion of two isomeric forms. The luminescence behavior of the titled clusters has been studied. All the compounds exhibit efficient sky-blue room-temperature phosphorescence both in solution and in the solid state with maximum quantum yield of 76%. The theoretical DFT calculations of the electronic structures demonstrated the difference in photophysical properties of the compounds depending on their structural topology.

ChemInform Abstract: Simple and Efficient One‐Pot Synthesis of Imidazo[1,2‐a]pyridines Catalyzed by Magnetic Nano‐Fe3O4—KHSO4·SiO2.

AbstractA facile and straightforward synthesis of imidazopyridines (IV) and (VI) is achieved by employing the title system‐catalyzed three‐component reaction of aminopyridine (I), aliphatic and aromatic aldehydes (II) and (V), and aliphatic and aromatic alkynes (III).

ChemInform Abstract: Synthesis of Bi‐ and Tricyclic 1,2‐Dihydroquinoline Derivatives from Arylamines and Alkynes by a Consecutive Zinc‐Ammonium Salt Catalysis.

AbstractLinear and cyclic secondary amines are treated with terminal aliphatic and aromatic alkynes in the presence of a two‐catalyst system to afford the desired bi‐ and tricyclic quinoline derivatives.

Zn–Co Double Metal Cyanides as Heterogeneous Catalysts for Hydroamination: A Structure–Activity Relationship

Zn–Co double metal cyanide (DMC) materials are effective heterogeneous catalysts for intermolecular hydroaminations. Using the reaction of 4-isopropylaniline with phenylacetylene as a test, the effect of different catalyst synthesis procedures on the catalytic performance is examined. The best activities are observed for double metal cyanides with a cubic structure and prepared with a Zn2+ excess, and for nanosized particles prepared via a reverse emulsion synthesis. Detailed study of the active Zn2+ sites in the cubic material by EXAFS gives evidence for coordinative vacancies around the Zn, with four cyanide ligands in close proximity of the Zn. The substrate scope of the hydroaminations was successfully expanded to both aromatic and aliphatic alkynes and other aromatic and aliphatic amines. Even with styrenes the reaction proceeded with aromatic amines. The DMC catalysts are truly heterogeneous, possess a high thermal stability and are perfectly reusable.

Chiral NCN Pincer Rhodium(III) Complexes with Bis(imidazolinyl)phenyl Ligands: Synthesis and Enantioselective Catalytic Alkynylation of Trifluoropyruvates with Terminal Alkynes

AbstractA series of new chiral C2‐symmetrical NCN pincer rhodium(III) complexes with bis(imidazolinyl)phenyl ligands have been conveniently synthesized from easily available materials. The complexes were subsequently applied in the enantioselective addition of terminal alkynes to trifluoropyruvates. With catalyst loading of 1.5–3.0 mol%, the alkynylation of ethyl or methyl trifluoropyruvate with a variety of electronically and structurally diverse terminal alkynes gave the optically active trifluoromethyl‐substituted tertiary propargylic alcohols with enantioselectivities of up to >99% ee and high yields. Although good to excellent enantioselectivities (85–98% ee) could be achieved only for some of the aliphatic terminal alkynes under the optimized conditions, the enantioselectivities were consistently excellent (94% to >99% ee) in the case of aromatic as well as heteroaromatic alkynes and enynes.

Conformations and CH/π Interactions in Aliphatic Alkynes and Alkenes

The carbon 1s photoelectron spectra of a series of aliphatic alkynes and alkenes that have the possibility of possessing two or more conformers have been recorded with high resolution. The two conformers of 2-hexyne and 4-methyl-1-pentyne, anti and gauche, have been identified and quantified from an analysis of their carbon 1s photoelectron spectra, yielding 30 ± 5% and 70 ± 6% anti conformers, respectively. In the case of 1-hexyne, the photoelectron spectrum is shown to provide partial information on the distribution of conformers. Central to these analyses is a pronounced ability of the C1s photoemission process to distinguish between conformers that display weak γ-CH/π hydrogen bonding and those that do not. For the corresponding alkene analogs, similar analyses of their C1s photoelectron spectra do not lead to conclusive information on the conformational equilibria, mainly because of significantly smaller chemical shifts and higher number of conformers compared with the alkynes.

Acid‐Catalyzed Hydration of Alkynes in Aqueous Microemulsions

Terminal aromatic alkynes are converted rapidly into ketones in a regioselective manner by treatment of their microemulsions with 0.33 M mineral acid between 80 and 140 °C. Internal and aliphatic acetylenes are likewise hydrated, but require longer reaction periods. The products are easily isolated from the reaction mixtures by phase separation. Replacement of H2 O by D2 O leads to the formation of trideuteriomethyl ketones.

ChemInform Abstract: Asymmetric Hydroalkynylation of Norbornadienes Promoted by Chiral Iridium Catalysis.

AbstractThe reaction of substituted norbornene derivatives with aromatic and aliphatic terminal alkynes proceeds with high level of enantioselectivities and tolerates a wide range of functional groups.

ChemInform Abstract: Importance of Bases on the Copper‐Catalyzed Oxidative Homocoupling of Terminal Alkynes to 1,4‐Disubstituted 1,3‐Diynes.

AbstractTerminal aliphatic and aromatic alkynes are successfully subjected to homocoupling in the absence of additives and solvent.

Efficient Synthesis of a (Z)-3-Methyleneisoindolin-1-one Library Using Cu(OAc)2•H2O/DBU under Microwave Irradiation

Microwave-promoted efficient synthesis of a (Z)-3-methyleneisoindolin-1-one library from 2-bromobenzamides and terminal alkynes using Cu(OAc)2•H2O/DBU is described. Various benzamide substituents, ring substitutions, including heteroaryl, aryl acetylenes and aliphatic alkynes, could be applied to afford the desired products in good to moderate yield with high stereoselectivity. It is noteworthy that DBU maybe play a dual role as not only the base, but also as a ligand for copper. The reaction is catalyzed by the complex of Cu(OAc)2•H2O and DBU without other additives.

P,P,P-Trihalobenzo-1,3,2-Dioxaphopholes in the Reaction with Aliphatic Acetylenes and Diacetylenes: Synthesis of New Phosphacoumarins

Bis(benzo[e]-1,2-oxaphosphinin-2-oxid-4(7)-yl)butane (-benzene) derivatives were synthesized for the first time both on the basis of reactions of diacetylene with P,P, P-trihalobenzo-1,3,2-dioxaphopholes and on the basis of reactions of bis(P,P,P-trihalobenzo-1,3,2-dioxaphosphol-5-yl)bytane (-benzene) with phenylacetylene.

Mesoporous silica-supported copper-catalysts for homocoupling reaction of terminal alkynes at room-temperature

Amine-functionalized mesoporous silica-supported copper catalysts SBA-15@amine–Cu and SBA-15@Oamine–Cu were prepared and proved to be efficient and reusable for homocoupling of terminal alkynes at room temperature with air as the oxidant. SBA-15@amine–Cu exhibited better recyclability than SBA-15@Oamine–Cu. The differences in the catalytic performances of the catalysts could be ascribed to catalyst structure and the interaction between copper and the supports. The as-prepared catalysts were systematically characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES), high resolution-transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and nitrogen physical adsorption. The analysis indicated that the mesoporous structure of the materials was retained during the immobilization process. XPS results suggested that the as-prepared catalysts were not obtained by a simple physical adsorption of CuCl on the supports. It is noted that, for aliphatic alkynes, the catalytic activity of SBA-15@amine–Cu is even higher than that of the homogeneous copper catalytic system and that of some previously reported heterogeneous systems.

Copper-catalyzed distannylation of alkynes

A copper(I)-phosphine complex has been found to facilely promote the distannylation of alkynes with the aid of a base, where a catalytically generated Cu-Sn species serves as a key intermediate. The broad versatility of the copper catalysis has been demonstrated by the facile distannylation of unfunctionalized aliphatic alkynes, being hardly achievable with the conventional palladium catalysts.

Ligand‐Free Synthesis of 1,4‐Disubstituted‐1,3‐diynes by Iron/Copper Cocatalyzed Homocoupling of Terminal Alkynes

AbstractA simple and efficient protocol for Fe/Cu cocatalyzed oxidative homocoupling reaction of terminal alkynes to symmetrical 1,4‐disubstituted‐1,3‐diynes was presented. The results showed that both CuBr and FeCl3 played crucial roles in the reaction. It is noteworthy that this protocol employs mild, efficient, aerobic and ligand free conditions. The alkynes, including aromatic, heteroaromatic and aliphatic alkynes, were transformed into the corresponding 1,3‐diynes in good to excellent yields.

Indium-Promoted Allylation of Alkynes with Allylic Alcohols: Highly Regioselective Synthesis of Halogen-Substituted 1,4-Dienes

Indium-promoted allylation of alkynes by direct use of allyl alcohols as the allylating agents has been developed under mild conditions, in which a wide range of allylic alcohols and alkynes (both aromatic and aliphatic alkynes) could be tolerated, and the corresponding halogen-substituted 1,4-dienes were obtained in moderate to excellent yields.

Palladium‐Catalyzed Carbonylative Coupling of Aryl Iodides and Benzyl Acetylenes to 3‐Alkylidenefuran‐2‐ones under Mild Conditions and Its Density Functional Theory Modeling

A general and efficient method for the palladium-catalyzed carbonylative coupling of aryl iodides to benzyl acetylenes has been developed. Various furanones have been prepared in excellent yields from their corresponding benzyl acetylenes at room temperature under a CO atmosphere. For aliphatic alkynes, their corresponding alkynones were obtained in good yields. Detailed DFT calculations have also been carried out to understand the reaction pathway and the most probable reaction mechanism has been proposed.

ChemInform Abstract: One‐Pot Three‐Component Click Reaction of Cyclic Sulfates and Cyclic Sulfamidates.

AbstractAlkyl sulfate triazoles (III) and (V) are efficiently synthesized by the reaction of cyclic sulfates (I) with aliphatic and aromatic terminal alkynes (II) and sodium azide under microwave irradiation.

ChemInform Abstract: General and Selective Head‐to‐Head Dimerization of Terminal Alkynes Proceeding via Hydropalladation Pathway.

AbstractAromatic, heteroaromatic and aliphatic alkynes, bearing a wide range of functional groups can be applied.