Aromatic Terminal Alkynes Research Articles

Organophosphate‐accelerated copper‐catalyzed C(sp2)–C(sp) Sonogashira‐type cross couplings

A dramatic acceleration in copper‐catalyzed Sonogashira‐type reactions was observed when an organophosphate was used as additive. The catalyst systems featuring low copper loading (0.5 mol% < Cu < 5 mol%) gave Sonogashira‐type products with a broad scope of aromatic and aliphatic terminal alkynes as well as aryl iodides in good to excellent yields. Among the organophosphate/copper catalytic systems, that of 4 mol% Cu(OTf)2/10 mol% (R)‐(−)‐1,1′‐binaphthyl‐2,2′‐diyl hydrogenphosphate exhibited the highest catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.

Homo-Coupling of Terminal Alkynes Using a Simple, Cheap Ni(dppe)Cl2/Ag2O Catalyst System

A simple Ni(dppe)Cl2/Ag2O combination has been established as an efficient catalyst system for the homo-coupling of aromatic terminal alkynes. This reaction proceeds under mild conditions and can be applied to alkynone substrates. Various aromatic 1,3-diynes were obtained in good to excellent yields.

Ortho-Alkenylation of anilines with aromatic terminal alkynes over nanosized zeolite beta

Synthesis of 1,1-diarylethylenes derivatives from anilines and aromatic terminal alkynes over a nanosized zeolite beta catalyst is reported.

Stereoselective intermolecular nitroaminoxylation of terminal aromatic alkynes: trapping alkenyl radicals by TEMPO.

The vinyl radical is one of the most unstable organic radicals. It is demonstrated that a nitro radical attacks phenylacetylene and makes the phenyl ring deconjugated with a double bond so that the resulting vinyl radical may be stabilized by delocalization to the phenyl ring's π orbital and easily trapped by TEMPO. It is noteworthy that all desired products were obtained in moderate to good yields in an (E)-configuration.

Copper-catalyzed enantioselective allylic alkylation of terminal alkyne pronucleophiles.

The copper-catalyzed enantioselective allylic alkylation of terminal alkynes with primary allylic phosphates was developed by the use of a new chiral N-heterocyclic carbene ligand bearing a phenolic hydroxy group at the ortho position of one of the two N-aryl groups. This reaction occurred with excellent γ-branch regioselectivity and high enantioselectivity, forming a controlled stereogenic center at the allylic/propargylic position. Various terminal alkynes, including silyl, aliphatic, and aromatic alkynes, could be used directly without premetalation of the C(sp)-H bond. On the basis of the results of experiments using an isomeric secondary allylic phosphate, which gave a branched product through an α-selective substitution reaction with retention of configuration, a reaction pathway involving 1,3-allylic migration of Cu in a ([σ + π]-allyl)copper(III) species is proposed.

ChemInform Abstract: Cu(II) Complex Heterogenized on SBA‐15: A Highly Efficient and Additive‐Free Solid Catalyst for the Homocoupling of Alkynes.

A Cu(II) complex has been heterogenized on SBA-15 by functionalization of SBA-15 with (N1-propylethane-1,2-diamine) triethoxysilane (NN-SBA-15) followed by anchoring of 2-pyridinecarboxaldehyde through Schiff's base formation between the terminal –NH2 and the aldehyde group of 2-pyridinecarboxaldehyde (Py-NN-SBA-15), and finally, copper(II) was immobilized through complexation. Copper(II) complex heterogenized on SBA-15 (Cu(II)-SBA-15) has been thoroughly characterized by different techniques such as N2 sorption, small-angle X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and solid-state 13C CP-MAS NMR spectroscopy. Cu(II)-SBA-15 is an efficient heterogenized solid catalyst for the oxidative homocoupling of phenyl acetylene into 1,4-diphenylbuta-1,3-diyne with a yield of 97%, even in the absence of palladium, co-catalyst and base additives. In the case of the homocoupling of other aromatic and aliphatic terminal alkynes, the yields were 85–98%.

ChemInform Abstract: Copper‐Catalyzed Selective Semihydrogenation of Terminal Alkynes with Hypophosphorous Acid.

AbstractThe optimized conditions allow the selective semihydrogenation of a broad range of terminal aromatic and aliphatic alkynes to afford the corresponding alkenes in high yields.

Palladium-catalyzed oxidative domino carbocyclization-carbonylation-alkynylation of enallenes.

An oxidative carbocyclization-carbonylation-alkynylation reaction cascade has been developed using catalytic amounts of palladium(II) salts. The domino reaction proceeds efficiently, giving the corresponding ynones in good to excellent yields under operationally simple conditions. A wide range of aromatic and aliphatic terminal alkynes with various functional groups are tolerated under the reaction conditions.

Pd Nanoparticles Immobilized on Nanosilica Triazine Dendritic Polymer: A Reusable Catalyst for the Synthesis of Mono‐, Di‐, and Trialkynylaromatics by Sonogashira Cross‐Coupling in Water

AbstractPalladium nanoparticles immobilized on nano‐silica triazine dendritic polymer (Pdnp‐nSTDP) was found to be a highly effective catalyst for the Sonogashira cross‐coupling of aryl halides (iodides, bromides, and chlorides) with aromatic and aliphatic terminal alkynes. This reaction was best performed in water as a green solvent in the presence of just 0.01 mol‐% of the catalyst at room temperature. Efficient synthesis of V‐ and star‐shaped polyalkynylated molecules with a benzene, pyridine, or pyrimidine central core was also achieved through Sonogashira cross‐coupling of dihalo and trihalo aromatics with terminal alkynes in the presence of this catalytic system. The Pdnp‐nSTDP catalyst was easily recovered and reused several times without significant loss of reactivity.

Gem‐Selective Cross‐Dimerization and Cross‐Trimerization of Alkynes with Silylacetylenes Promoted by a Rhodium–Pyridine–N‐Heterocyclic Carbene Catalyst

AbstractThe gem‐selective cross‐dimerization and ‐trimerization of silylacetylenes with alkynes through CH activation using a rhodium(I)–pyridine–N‐heterocyclic carbene catalyst have been developed. This reaction is applied to various aliphatic or aromatic terminal alkynes, internal alkynes, and gem‐1,3‐disubsituted enynes to afford the corresponding enynes and dienynes with high regio‐ and stereoselectivities and in good isolated yields (up to 91 %).

ChemInform Abstract: Hydration of Aromatic Terminal Alkynes Catalyzed by Iron(III) Sulfate Hydrate under Chlorine‐Free Conditions.

Abstract The hydration of aromatic terminal alkynes performed in acetic acid in the presence of catalytic hydrate iron III sulfate, Fe 2 (SO 4 ) 3 · n H 2 O (4–9 mol %), yields the derived aryl methyl ketones with good to excellent yields. Under comparable conditions (18 mol %, 95 °C, 24 h), bifunctional substrates were transformed into the monoacetyl or the diacetyl derivatives, depending on the structure of the aromatic diyne. The reaction is compatible with aryl substituents of different nature and ring positions, including hydroxyl, carbonyl groups, and cumulated hydrocarbons. The soft character of the non nucleophilic sulfate anion allows for activation of the triple bond toward carbon oxygen bond formation in the Bronsted acidic medium. The proposed protocol is based on readily available and non toxic materials, in the absence of chlorine atoms in either the solvent or the metal catalyst.

ChemInform Abstract: Mild‐Condition Synthesis of Allenes from Alkynes and Aldehydes Mediated by Tetrahydroisoquinoline (THIQ).

A practical 1,2,3,4-tetrahydroisoquinoline (THIQ)-mediated synthesis of 1,3-disubstituted allenes from terminal alkynes and aldehydes under mild conditions in the presence of CuBr first and then ZnI2 was reported. This telescoped allene synthesis reaction includes three consecutive steps and two reactions: first, a room-temperature CuBr-catalyzed synthesis of propargylamines, exo-yne-THIQs, from terminal alkynes, aldehydes, and THIQ, then filtration of the CuBr catalyst, and finally the ZnI2-mediated allene synthesis from the generated exo-yne-THIQs under mild conditions (either at room temperature or heating at 50 or 75 °C). A wide range of aliphatic or aromatic aldehydes and terminal alkynes are tolerated, affording the allene products in up to 92% yield. Especially, temperature-sensitive aldehydes can be used in the reaction system. Preliminary exploration of the asymmetric allene synthesis has also been conducted, and a moderate enantioselectivity has been achieved. Finally, the relative reactivities of several secondary amines were compared with THIQ, showing that THIQ is the best of these amines in the synthesis of allenes under mild reaction conditions.

Neutral and Cationic NCN Pincer Platinum(II) Complexes with 1,3-Bis(benzimidazol-2′-yl)benzene Ligands: Synthesis, Structures, and Their Photophysical Properties

A series of neutral pincer Pt(II) chloride complexes 3–7 were first synthesized via the reaction of 1,3-bis(N-substituted benzimidazol-2′-yl) benzene (bzimb) ligands 2a–e with K2PtCl4 in refluxing HOAc. By treatment of complex 3 with KI and aromatic terminal alkynes in methanolic NaOH, the Pt(II) iodide complex 8 and Pt(II) acetylide complexes 9–11 were then obtained. Cationic Pt(II) complexes 12–15 were finally produced by the chloro-substitution reaction of complex 3 with AgOTf and several neutral N-donor ligands. With these new compounds in hand, various characterizations including elemental analysis, NMR, and IR were carried out to investigate their properties. On the basis of the X-ray single-crystal structure analysis of complexes 3–5, 8, 9, and 12, weak intermolecular interactions including π···π stacking and/or hydrogen bonds were found to be responsible for their assembly. After full investigation of the electronic absorption and photoluminescent properties of the Pt(II) complexes 3–15, time-depe...

ChemInform Abstract: Palladium/Copper Complexes Co‐Catalyzed Highly Enantioselective Ring Opening Reaction of Azabenzonorbornadienes with Terminal Alkynes.

AbstractThe reaction tolerates a wide range of aromatic and aliphatic terminal alkynes and proceeds with enantioselectivities up to <99.9% e.e.

Hydration of aromatic terminal alkynes catalyzed by iron(III) sulfate hydrate under chlorine-free conditions

The hydration of aromatic terminal alkynes performed in acetic acid in the presence of catalytic hydrate ironIII sulfate, Fe2(SO4)3·nH2O (4–9mol%), yields the derived aryl methyl ketones with good to excellent yields. Under comparable conditions (18mol%, 95°C, 24h), bifunctional substrates were transformed into the monoacetyl or the diacetyl derivatives, depending on the structure of the aromatic diyne. The reaction is compatible with aryl substituents of different nature and ring positions, including hydroxyl, carbonyl groups, and cumulated hydrocarbons. The soft character of the non nucleophilic sulfate anion allows for activation of the triple bond toward carbonoxygen bond formation in the Brønsted acidic medium. The proposed protocol is based on readily available and non toxic materials, in the absence of chlorine atoms in either the solvent or the metal catalyst.

Cu(ii) complex heterogenized on SBA-15: a highly efficient and additive-free solid catalyst for the homocoupling of alkynes

A Cu(II) complex has been heterogenized on SBA-15 by functionalization of SBA-15 with (N1-propylethane-1,2-diamine) triethoxysilane (NN-SBA-15) followed by anchoring of 2-pyridinecarboxaldehyde through Schiff's base formation between the terminal –NH2 and the aldehyde group of 2-pyridinecarboxaldehyde (Py-NN-SBA-15), and finally, copper(II) was immobilized through complexation. Copper(II) complex heterogenized on SBA-15 (Cu(II)-SBA-15) has been thoroughly characterized by different techniques such as N2 sorption, small-angle X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and solid-state 13C CP-MAS NMR spectroscopy. Cu(II)-SBA-15 is an efficient heterogenized solid catalyst for the oxidative homocoupling of phenyl acetylene into 1,4-diphenylbuta-1,3-diyne with a yield of 97%, even in the absence of palladium, co-catalyst and base additives. In the case of the homocoupling of other aromatic and aliphatic terminal alkynes, the yields were 85–98%.

Direct functionalization of unactivated C–H bonds catalyzed by group 3–5 metal alkyl complexes

This perspective summarizes direct C-H bond functionalization reactions catalyzed by group 3-5 metal alkyl complexes. Metal-carbon bonds of group 3-5 metals have potentially high reactivity toward both C-H bond activation reactions through the intrinsic σ-bond metathesis pathway and insertion of unsaturated organic molecules. Upon the combination of these two elemental steps, direct C-H bond functionalization reactions of (hetero)aromatic compounds, methane, alkylamines, and terminal alkynes, proceed through C(sp)-H, C(sp(2))-H, and C(sp(3))-H bond activation reactions. Here we review as catalysts for these transformations not only simple metallocene complexes but also non-metallocene complexes supported by a variety of ligands, which are often superior in terms of catalyst design and catalytic activity.

Mild-Condition Synthesis of Allenes from Alkynes and Aldehydes Mediated by Tetrahydroisoquinoline (THIQ)

A practical 1,2,3,4-tetrahydroisoquinoline (THIQ)-mediated synthesis of 1,3-disubstituted allenes from terminal alkynes and aldehydes under mild conditions in the presence of CuBr first and then ZnI2 was reported. This telescoped allene synthesis reaction includes three consecutive steps and two reactions: first, a room-temperature CuBr-catalyzed synthesis of propargylamines, exo-yne-THIQs, from terminal alkynes, aldehydes, and THIQ, then filtration of the CuBr catalyst, and finally the ZnI2-mediated allene synthesis from the generated exo-yne-THIQs under mild conditions (either at room temperature or heating at 50 or 75 °C). A wide range of aliphatic or aromatic aldehydes and terminal alkynes are tolerated, affording the allene products in up to 92% yield. Especially, temperature-sensitive aldehydes can be used in the reaction system. Preliminary exploration of the asymmetric allene synthesis has also been conducted, and a moderate enantioselectivity has been achieved. Finally, the relative reactivities of several secondary amines were compared with THIQ, showing that THIQ is the best of these amines in the synthesis of allenes under mild reaction conditions.

ChemInform Abstract: Highly Efficient AgBF4‐Catalyzed Synthesis of Methyl Ketones from Terminal Alkynes.

A silver-catalyzed highly efficient synthesis of a wide range of methyl ketones from terminal alkynes is described. The reactions are conducted under convenient conditions and provide products with excellent regioselectivity in moderate to excellent yields, with broad substrate scope, including a variety of aromatic and aliphatic terminal alkynes.

Ionic Liquid Iodinating Reagent for Mild and Efficient Iodination of Aromatic and Heteroaromatic Amines and Terminal Alkynes

Hexamethylene bis(N-methylimidazolium) bis(dichloroiodate) (HMBMIBDCI), an ionic liquid iodinating reagent, have been prepared and characterized. Its ability to perform iodination reactions with a variety of substrates has been explored. In general, iodination reactions of aromatic and heteroaromatic amines proceed with good yields in the absence of solvent. Reactions of terminal alkynes in the presence of 1,8-diazabicyclo [5.4.O] undec-7-ene and tetrahydrofuran have been investigated as well. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource: Full experimental and spectral details.]