The application of polymer-bound carbonylcobalt(0) species in linker chemistry and catalysis

Carbonylcobalt(0) species have been used as linkers between alkynes and a polymer support for the first time. The alkynes may be loaded indirectly onto a phosphine functionalised polymer via their hexacarbonyldicobalt(0) complex, or directly onto a cobalt coated polymer. The alkynes have been released either as alkynes, thus providing a traceless method of immobilising alkynes, or by reaction with an alkene to generate a cyclopentenone via the Pauson-Khand reaction. The cobalt coated polymers produced during this study were shown to catalyse the Pauson-Khand reaction.     

Synthesis of naphthalenes through three-component coupling of alkynes, Fischer carbene complexes, and benzaldehyde hydrazones via isoindole intermediates

The synthesis of naphthalene derivatives through three-component coupling of 2-alkynylbenzaldehyde hydrazones with carbene complexes and electron-deficient alkynes has been examined. The reaction involves formation of an isoindole derivative, followed by intramolecular Diels-Alder reaction, followed by nitrene extrusion. The reaction was highly regioselective using unsymmetrical alkynes.     

Chromium-mediated synthesis of polycyclic aromatic compounds from halobiaryls

[reaction: see text] Reaction of 2,2'-dihalobiphenyl with butyllithium followed by the addition of chromium(III) chloride and alkynes afforded the corresponding phenanthrene derivatives via formal [4 + 2] cycloaddition. A variety of alkynes could be used for this reaction, such as alkyl, aryl, silyl, and alkoxycarbonyl alkynes. Repetitive process of the reaction gave more extended polycyclic compounds such as benzo[g]chrysene and azacyclopentaphenalene derivatives.     

Highly stereoselective one-pot procedure to prepare bis- and tris-chalcogenide alkenes via addition of disulfides and diselenides to terminal alkynes

We present here the reaction of diorganoyl dichalcogenides with terminal alkynes under catalyst-free conditions, by a one-pot procedure, to prepare bis- and tris-chalcogenide alkenes selectively, avoiding the previous preparation of chalcogen alkynes. The reaction proceeded cleanly under mild reaction conditions, and the addition of dichalcogenides to alkynes occurred stereoselectively to give exclusively the corresponding Z isomers. We observed that the selectivity control was governed by the effective participation of the hydroxyl group from propargyl alcohols. In addition, the bis-chalcogenide alkenes were exclusively obtained with propargyl alcohol having the acidic hydroxyl group proton. Conversely, the alkynes with no potentially acidic hydroxyl group proton, at propargyl positions, gave exclusively the tris-chalcogenide alkenes.     

A general and regioselective synthesis of cyclopentenone derivatives through nickel(0)-mediated [3 + 2] cyclization of alkenyl Fischer carbene complexes and internal alkynes

A broad range of substituted 2-cyclopentenone derivatives 3-6 are synthesized by the nickel(0)-mediated [3 + 2] cyclization reaction of chromium alkenyl(methoxy)carbene complexes 1 and internal alkynes 2. The reaction takes place with complete regioselectivity with both unactivated alkynes and activated alkynes (electron-withdrawing and electron-donating substituted alkynes). Representative cycloadducts containing boron and tin substituents are further demonstrated to be active partners in classical Pd-catalyzed C-C coupling processes to allow the production of 2-aryl- and 2-alkynyl-substituted cyclopentenones 9-13.     

Sequential catalytic process: synthesis of quinoline derivatives by AuCl3/CuBr-catalyzed three-component reaction of aldehydes, amines, and alkynes

A sequential catalytic process has been developed based on gold-catalyzed nucleophilic addition of terminal alkynes to imines, and gold-catalyzed intramolecular reaction of aromatic ring to alkynes. This one-pot reaction of aldehydes, amines, and alkynes gives quinoline derivatives in good yields.     

从贫电子炔烃出发的合成方法学研究

对十五年来本小组所研究的从贫电子炔烃出发的合成方法学进行回顾,分四方面加以叙述。(1)叔膦启动的反应,(2)贫电子炔烃的顺式卤氢化反应,(3)碳-钯键的质解反应;(亲核钯化-插入-质解串联反应),(4)二价钯催化的烯炔酯不对称环化反应。这四方面的反应可以分成二大类：一类是单由亲核试剂对贫电子叁键进攻所启动的;另一类是亲核试剂对过渡金属配位的叁键进攻所启动的。对反应发现的过程,研究的深入,机理的探讨,和新规律的发现等都进行了比较详细的讨论。     

Regioselective synthesis of indoles via reductive annulation of nitrosoaromatics with alkynes

[reaction: see text] Indoles are produced regioselectively and in moderate yields by two new processes: (a) from the [CpRu(CO)2]2-catalyzed reaction of nitrosoaromatics (ArNO) with alkynes under carbon monoxide and (b) in a two-step sequence involving the (uncatalyzed) reaction of ArNO with alkynes, followed by reduction of the intermediate adduct.     

Electrophilic trifluoromethylation by copper-catalyzed addition of CF3-transfer reagents to alkenes and alkynes

Regio- and stereoselective Cu-catalyzed addition of the above hypervalent iodine reagent to alkynes and alkenes was achieved. In the presence of CuI, the reaction is suitable to perform trifluoromethyl-benzoyloxylation and trifluoromethyl-halogenation of alkenes and alkynes. Electron-donating substituents accelerate the process, and alkenes react faster than alkynes emphasizing the electrophilic character of the addition reaction.     

Organocatalytic Oxidative Annulation of Benzamide Derivatives with Alkynes

Organocatalytic annulation by functionalization of benzamide derivatives with alkynes has been developed. We report a new approach of cycloaddition under mild reaction conditions using simple catalysts, such as iodobenzene and peracetic acid, as oxidant. Those novel, mild reaction conditions provided a straightforward synthesis of isoquinolones with fast reaction rate. Notable selectivity in annulation of unsymmetrically disubstituted alkynes was demonstrated.     

A synthesis of trisubstituted alkenes by a Ru-catalyzed addition

Catalyzed by ruthenium trisacetonitrile hexafluorophosphate 4, the Alder-ene type reaction of alkenes and internal alkynes provides an effective way to synthesize trisubstituted alkenes. Unlike most typical olefination protocols, this reaction is atom economical, and affords trisubstituted alkenes with defined olefin geometry. The regioselectivity can be explained invoking a steric argument based on the proposed mechanism. The first C-C bond formation generally involves sterically less hindered carbons of the alkenes and alkynes. Modest to very high regioselectivity can be achieved depending on the steric difference of the two substituents of alkynes.     

Regiospecific synthesis of 2-allyl-1,2,3-triazoles by palladium-catalyzed 1,3-dipolar cycloaddition

2-Allyl-1,2,3-triazoles were prepared by the palladium-catalyzed three component coupling (TCC) reaction of alkynes, allyl methyl carbonate and trimethylsilyl azide. A π-allylpalladium azide complex, which undergoes the 1,3-dipolar cycloaddition with alkynes, is proposed as a key intermediate in the TCC reaction.     

Aerobic Direct Dioxygenation of Terminal/Internal Alkynes to α-Hydroxyketones by an Fe Porphyrin Catalyst

We herein report a new synthetic method for the preparation of α-hydroxyketones by the dioxygenation of alkynes. The reaction proceeds at room temperature under the action of Fe porphyrin and pinacolborane under air as a green oxidant to produce α-hydroxyketones. The mild reaction conditions allow chemoselective oxidation with functional group tolerance. Terminal alkynes in addition to internal alkynes are applicable, affording unsymmetrical α-hydroxyketones that are difficult to obtain by any reported dioxygenation of unsaturated C−C bonds.     

Palladium-catalyzed arylation of enynes and electron-deficient alkynes using diaryliodonium salts

A new single-pot procedure for the synthesis of aryl alkynes is described. Palladium catalyzes the coupling reaction of diaryliodonium compounds with enynes and electron-deficient alkynes to give aryl alkynes in good yields.     

Three characteristic reactions of alkynes with metal compounds in organic synthesis

Alkynes have two sets of mutually orthogonal π‐bonds that are different from the π‐bonds of alkenes. These π‐bonds are able to bond with transition metal compounds. Alkynes easily bond with the various kinds of compounds having a π‐bond such as carbon monoxide, alkenes, other alkynes and nitriles in the presence of the transition metal compounds. The most representative reaction of alkynes is called the Pauson–Khand reaction. The Pauson–Khand reactions include the cyclization of alkynes with alkenes and carbon monoxide in the presence of cobalt carbonyls. Similar Pauson–Khand reactions also proceed in the presence of other transition metal compounds. These reactions are the first type of characteristic reaction of alkynes. Other various kinds of cyclizations with alkynes also proceed in the presence of the transition metal compounds. These reactions are the second type of characteristic reaction of alkynes. These include cyclooligomerizations and cycloadditions. The cyclooligomerizations include mainly cyclotrimerizations and cyclotetramerizations, and the cycloadditions are [2 + 2], [2 + 2 + 1], [2 + 2 + 2], [3 + 2], [4 + 2], etc., type cycloadditions. Alkynes are fairly reactive because of the high s character of their σ‐bonds. Therefore, simple coupling reactions with alkynes also proceed besides the cyclizations. The coupling reactions are the third type of characteristic reactions of alkynes in the presence of, mainly, the transition metal compounds. These reactions include carbonylations, dioxycarbonylations, Sonogashira reactions, coupling reactions with aldehydes, ketones, alkynes, alkenes and allyl compounds. Copyright © 2008 John Wiley & Sons, Ltd.     

Palladium-catalyzed cross-coupling reaction of aryl trimethoxysilanes with terminal alkynes

A palladium-catalyzed cross-coupling reaction of aryl trimethoxysilanes with terminal alkynes was described. Thus, di-substituted alkynes were prepared in moderate to good yields. The electron-deficient terminal alkynes also worked well in the procedure.     

Metal free synthesis of quinoxalines from alkynes via a cascade process using TsNBr2

A metal free protocol for the synthesis of quinoxalines from alkynes has been developed. The reaction was carried out by treating alkynes with TsNBr₂ in presence of O-phenylenediamines in a mixture of acetonitrile and water (9:1). This one-pot reaction proceeds via an oxidative transformation of alkynes to α,α-dibromoketones in presence of TsNBr₂ and eventually to quinoxalines in presence of 1,2-diamines in a cascade process.     

InCl3 and ZrCl4 catalyzed regioselective reaction of 2,2′-dihydroxybiphenyl with terminal alkynes: synthesis of new dibenzo[d,f][1,3]dioxepines

The regioselective reaction of 2,2′-dihydroxybiphenyl with terminal alkynes was found to be rapidly catalyzed by InCl₃ and ZrCl₄. The chemoselectivity of catalysts and alkynes for biphenol over water, together with the reaction mechanism are discussed in details.     

Silver(I)‐Catalyzed Hydroazidation of Ethynyl Carbinols: Synthesis of 2‐Azidoallyl Alcohols

The hydroazidation of alkynes is the most straightforward pathway to synthetically useful vinyl azides. However, a general hydroazidation of alkynes remains elusive. Herein, a chemo‐ and regioselective transformation of ethynyl carbinols into vinyl azides is described. This reaction produces a wide variety of 2‐azidoallyl alcohols with high efficiency and in good to excellent yields. These compounds constitute a new class of densely functionalized synthetic intermediates. Their synthetic potential has been demonstrated by further transformations into NH aziridines. The mechanistic aspects of the reaction will attract the attention of chemists working on alkyne chemistry and silver catalysis. The findings that are described in this paper represent significant advances in the regioselective hydroelementation of alkynes and open a new reaction manifold for exploitation.     

Rh(I)-catalyzed carbonylative cyclization reactions of alkynes with 2-bromophenylboronic acids leading to indenones

The Rh-catalyzed reaction of alkynes with 2-bromophenylboronic acids involves carbonylative cyclization to give indenones. The key steps in the reaction involve the addition of an arylrhodium(I) species to an alkyne and the oxidative addition of C-Br bonds on the adjacent phenyl ring to give vinylrhodium(I) species II. The regioselectivity depends on both the electronic and the steric nature of the substituents on the alkynes. A bulky group and an electron-withdrawing group favor the -position of indenones. In the case of silyl- or ester-substituted alkynes, the regioselectivity is extremely high. The selectivity increases in the order SiMe3 > COOR > aryl > alkyl. The reaction of norbornene with 2-bromophenylboronic acids under 1 atm of CO gives the corresponding indanone derivative. The reaction of alkynes with 2-bromophenylboronic acids under nitrogen gives naphthalene derivatives, in which two molecules of alkynes are incorporated. A vinylrhodium complex similar to II can also be generated by a different route by employing 2-bromophenyl(trimethylsilyl)acetylene and arylboronic acids in the presence of Rh(I) complex as the catalyst, resulting in the formation of indenones. The reaction of 1-(2-bromophenyl)-hept-2-yn-1-one with PhB(OH)2 in the presence of Rh(I) complex also resulted in carbonylative cyclization to give an indan-1,3-dione derivative.