4289-20-7

In the presence of a nickel catalyst prepared from Ni(acac)2 and DIBALH (1/1) in situ, three-component coupling reaction of allyl chlorides, 1-alkynes, and alkynyltins yielded regio- and stereoselective 3,6-dien-1-ynes in THF.

Alkynylsilver cations, RCCAg2+ (where R = Me and Ph) have been prepared in the gas phase using multistage mass spectrometry experiments in a quadrupole ion trap mass spectrometer. Two methods were used: (i) electrospray ionisation (ESI) of a mixture of AgNO3 (in MeOH/H2O/acetic acid) and the alkyne carboxylic acid to yield the appropriate silver acetylide cations RCCAg2+, via a facile decarboxylation of the RCCCO2Ag2+ precursor; (ii) ESI of silver acetylides, RCCAg, which yields a cluster of the type, [(RCCAg)12Ag2Cl]+. Regardless of the method of preparation, these alkynylsilver cations, RCCAg2+, undergo ion-molecule reactions with allyliodide to yield the ionic products Ag 2I+ and [(RCCCH2CHCH2)Ag] +. The CID spectrum of [(PhCCCH2CHCH2)Ag] + was compared to that of an authentic sample of the silver adduct of 5-phenyl-1-penten-4-yne. Both ions fragment to yield Ag+ and the radical cation, PhCCCH2CHCH2+, confirming that C-C bond coupling has taken place in the gas phase. DFT calculations were carried out on these C-C bond coupling reactions for the system R = Me. The reaction is highly exothermic and involves the initial coordination of the allyliodide to both silver atoms, with the iodine coordinating to one atom and the alkene moiety coordinating to the other. The overall mechanism of C-C bond coupling involves oxidative addition of the allyliodide followed by reductive elimination of RCCCH2CHCH2, to ultimately yield two sets of reaction products: (i) Ag2I+ and RCCCH 2CHCH2; and (ii) [(RCCCH2CHCH 2)Ag]+ and AgI. The Royal Society of Chemistry 2013.

Fe3O4-Pd nanocomposite having core-satellite heterostructure, prepared through the reaction of Pluronic polymer (P123, PEO19-PPO69-PEO19)-coated Fe3O 4 nanoparticle and Na2

One-pot three-component reactions using copper(i) acetylide, azide, allyl iodide, and NaOH have been developed. The reactions proceed smoothly at room temperature to afford 5-allyl-1,2,3-triazoles, which can be further transformed into a variety of 1,2,3-triazole-fused bi-/tricyclic scaffolds. This method offers the most efficient, convenient, and practical route towards useful polycyclic scaffolds in moderate to excellent yields.

A Pd-catalyzed regio- and stereoselective alkynylallylation of a specific C?C σ bond in cyclopropenes, using allyl propiolates as both allylation and alkynylation reagents, has been achieved for the first time. By merging selective C(sp2)-C(sp3) bond scission with conjunctive cross-couplings, this decarboxylative reorganization reaction features fascinating atom and step economy and provides an efficient approach to highly functionalized dienynes from readily available substrates. Without further optimization, gram-scale products can be easily obtained by such a simple, neutral, and low-cost catalytic system with high TONs. DFT calculations afford a rationale toward the formation of the products and indicate that the selective insertion of the double bond of cyclopropenes into the C-Pd bond of ambidentate Pd complex and the subsequent nonclassical β-C elimination promoted by 1,4-palladium migration are critical for the success of the reaction.

We present herein an unprecedented allylative dicarbofunctionalization of alkynes with allylic alcohols. This simple catalytic procedure utilizes commercially available Ni(COD)2, triphenylphosphine, and inexpensive reagents, and delivers valuable skipped dienes and trienes with an all-carbon tetrasubstituted alkene unit in a highly stereoselective fashion. Preliminary mechanistic studies support the reaction pathway of allylnickelation followed by transmetalation in this dicarbofunctionalization of alkynes.

A copper(I)-mediated tandem three-component reaction using alkynes, azides, allyl iodides, CuI and NaNH 2 is developed. The reactions proceed smoothly at room temperature to afford 5-allyl-1,2,3-triazoles, which can be further converted into 1,2,3-triazole-fused tricyclic scaffolds. This method features an efficient one-pot cascade route using commercial alkynes and affords the corresponding 5-allyl-1,2,3-triazoles with high yields and good selectivity under mild reaction conditions.

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Allyl alkynoic esters were synthesized by the reaction of allyl amines and alkynoic acids via deaminative esterification. The reaction of allyl alkynoic esters with Pd(dba)2 and Xantphos in digylme at 110 °C for 12 h afforded the desired decarb

Chiral allenes are highly valuable as versatile synthetic intermediates and core skeletons of various functional organic molecules. Despite marked recent advances, the straightforward catalytic enantioselective synthesis of hydrocarbon allenes from readil

The gold(I)-catalyzed reaction of bromoalkynes with allylsilanes gives 1,4-enynes in a formal cross-coupling reaction. Mechanistic studies revealed the involvement of gold(I) vinylidenes or vinylidenephenonium gold(I) cations depending on the substituent on the bromoalkyne. In the case of bromo arylalkynes, the vinylidenephenonium gold(I) cations lead to 1,4-enynes via a 1,2-aryl rearrangement. The same reactivity has been observed in the presence of InBr3

It was found that the C(sp)?B(dan) bond of alkynyl?B(dan)s can be directly used for palladium-catalyzed carbon?carbon bond-forming reactions with aryl(alkenyl) halides and allylic carbonates as electrophiles, thus delivering unsymmetrical internal alkynes and unconjugated 1,4-enynes, respectively. With acyl chlorides as electrophiles, ynone synthesis is also promoted by a palladium catalyst with the assistance of a copper co-catalyst. These reactions can be achieved as more convenient one-pot reactions, without isolating the alkynyl?B(dan) formed in situ by the zinc-catalyzed dehydrogenative borylation of alkynes with HB(dan). In addition to direct C(sp)?B(dan) bond transformations, the C≡C bond in an alkynyl?B(dan) proved to be a promising scaffold for the construction of a multisubstituted alkene, which is synthesized by diboration of the C≡C?B(dan) moiety, leading to a triborylalkene followed by iterative regio- and stereoselective Suzuki?Miyaura cross-coupling reactions. As one example, the synthesis of the ethene with four different aryl groups, p-MeC6H4, p-MeOC6H4, p-NCC6H4, and p-F3CC6H4, was attained in high overall yield of 64% in six steps starting from the terminal alkyne, p-MeC6H4C≡CH. Besides these synthetic applications of the alkynyl?B(dan), the scope of the alkynyl substrate in the zinc-catalyzed dehydrogenative borylation was expanded to enhance the reliability as a provider of the alkynyl?B(dan). Consequently, 42 alkynes were found to participate in the dehydrogenative borylation as substrates; these are alkyl-, alkenyl-, aryl-, heteroaryl-, ferrocenyl-, silyl-, and borylalkynes, with or without a variety of functional groups. Lastly, a new method for preparing HB(dan), as a sulfide-free, cost-saving, and reaction-time-saving route, is disclosed. (Figure presented.).

A palladium-catalyzed asymmetric α-allylation of aldehydes with alkynes has been established by integrating the catalysis of enamine and chiral hydridopalladium complex that is reversibly formed from the oxidative addition of Pd(0) to chiral phosphoric acid. The ternary catalyst system, consisting of an achiral palladium complex, a primary amine, and a chiral phosphoric acid allows the reaction to tolerate a wide scope of α,α-disubstituted aldehydes and alkynes, affording the corresponding allylation products in high yields and with excellent levels of enantioselectivity.

An unprecedented acid- and ligand-controlled divergent allylation of indoles with unactivated skipped enynes via Pd hydride catalysis has been disclosed. This redox-neutral transformation went through multiple hydropalladation insertion, β-hydrogen elimin

An unprecedented acid- and ligand-controlled divergent allylation of indoles with unactivated skipped enynes via Pd hydride catalysis has been disclosed. This redox-neutral transformation went through multiple hydropalladation insertion, β-hydrogen elimination, π-σ-π isomerization, and allylic substitution steps. This method not only provides a platform for synthesizing indolenines and N-allylindoles but also allows facile access to functional 1,3-dienes with high atom and step economy.

An unprecedented palladium-catalyzed allylic alkylation of pronucleophiles with unactivated skipped enynes has been developed. This method provides a straightforward access to a wide array of 1,3-dienes without the need to preinstall leaving groups or employ extra oxidants. The reaction exhibited high atom economy, good functional group tolerance, excellent regioselectivities, and scalability. With D2O as cosolvent, deuterium could be incorporated in high efficiency.

In this work, the addition of Grignard reagents to arylsulfonylacetylenes, which undergoes an "anti-Michael addition", resulting in their alkynylation under very mild conditions is described. The simplicity of the experimental procedure and the functional

A novel decahydropyrene synthesis has been successfully developed involving a tandem rhodium-catalyzed C-H activation/intramolecular Diels-Alder reaction/1,3-dipolar cycloaddition cascade process by using diazole as a traceless directing group. The advantage of this one-pot strategy is a quite simple, efficient, highly stereoselective, and unique product structure.

The coupling reaction of aryl alkynyl carboxylic acids and allyl acetates was carried out in the presence of nickel catalyst to produce the allyl alkynes in good yields. The optimized condition is that alkynyl carboxylic acid (1.0 equiv), allyl acetate (2

The first copper-catalyzed formal carboboration of alkynes, in which a C-B bond and a C-C bond are created in a single catalytic cycle, is presented. The reaction proceeds with high regioselectivity and syn-stereoselectivity to form tri- and tetrasubstituted vinylboronic esters from commercially available bis(pinacolato)diboron. A subsequent cross-coupling reaction gives access to highly substituted alkenes.

The combination of two powerful cobalt-catalyzed carbon-carbon bond forming transformations, namely, the Diels-Alder and the 1,4-hydrovinylation reaction, in a tandem or a sequential one-pot procedure, opened up a concise and efficient route to polysubstituted aromatic systems and cyclohex-3-enone derivatives. Furthermore, ozonolysis of the latter products led to polycarbonyl compounds with tailored carbonyl group distances which could be characterized via their respective BF2-borinane complexes. The cobalt catalysts tolerated several functional groups, and a flexible approach to polyfunctionalized compounds in concise fashion was described.

An efficient coupling of terminal alkynes and CO2 in the presence of alkyl halides can be achieved under ambient conditions using a copper/phosphine catalyst system, providing facile access to a variety of functionalised alkyl 2-alkynoates.

Silver triflate was found to be an efficient catalyst for the cyclopropenation of internal alkynes using donor-/acceptor-substituted diazo compounds as carbenoid precursors. Highly substituted cyclopropenes, which cannot be synthesized directly via rhodium(II)-catalyzed carbenoid chemistry, can now be readily accessed.

Allylic halides and terminal alkynes couple under CuI catalysis in DMSO or DMF solution. In most cases, sodium carbonate or bicarbonate is sufficient to promote the reaction; less reactive alkynes require catalytic amounts of DBU. Bifunctional alkynes and halides can be reacted selectively according to the stoichiometry used. Trimethylsilyl, hydroxyl, ester and halide groups are tolerated in the alkyne. Most halides react without allylic rearrangement. The method is suitable for the synthesis of functionalized enynes.

Cyclic voltammetry and controlled-potential electrolysis were employed to study the catalytic reduction of five phenyl-conjugated haloalkynes by nickel(I) salen electro-generated at carbon cathodes in dimethylformamide containing tetramethylammonium tetrafluoroborate. Electrocatalytic reduction of 7-bromo- and 7-iodo-1-phenyl-1-heptyne affords the carbocyclic product, benzylidenecyclohexane, in up to 41 % yield, whereas under similar conditions reduction of 5-halo-1-phenyl-1-pentyne and 8-bromo-1-phenyl-1-octyne gives benzylidenecyclobutane and benzylidenecycloheptane, respectively, in very low yield (≤1 %). Dimers, alkynes, and alkenynes are other products formed from the phenyl-conjugated haloalkynes. Dimers (diphenylalkadiynes) derived from 5-halo-1-phenyl-1-pentyne and 8-bromo-1-phenyl-1-octyne are obtained in yields ranging from 85 to 93 %, whereas 1,14-diphenyltetradeca-1,13-diyne (the dimer produced from 7-halo-1-phenyl-1-heptyne) is found in yields of 45-51 %. To account for the formation of the various products, a mechanistic scheme that involves phenyl-conjugated alkynyl radicals arising from nickel(I) salen catalyzed cleavage of the carbon-halogen bond of each substrate was formulated. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.

A convenient and inexpensive ultrasound-assisted preparation of functionalized arylacetylenes using metallic lithium is reported.

Clean and high-yielding cross-coupling of alkynylzincs with allylic chlorides, bromides, or acetates exhibiting ≥ 98% regio-and stereoselectivity can be achieved by using 1 mol% of Pd(DPEphos)Cl2 and either 1:1 THF-DMF or pure DMF. This reaction provides a satisfactory route to 1,4-enynes via Pd-catalyzed alkynyl-allyl coupling. Georg Thieme Verlag Stuttgart.

A palladium-catalyzed 1,4-enyne synthesis was developed based the decarboxylative coupling of acetylides with allyl electrophiles. Stereochemical studies have implicated palladium-allyl-acetylides as intermediates. Thus, decarboxylative metalation was established as an environmentally benign alternative to transmetalation from alkynyl tin reagents. Copyright

Reactions of organometallic reagents with 1-(substituted ethynyl)-1H-1,2,3-benzotriazoles 5 derived from a variety of benzotriazolylmethyl ketones 3 afforded disubstituted acetylenes in synthetically useful yields.

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Copper-catalyzed cross-coupling of 1-iodoalkynes with organostannanes was readily achieved in the presence of CuI (10 mol%) in DMF at room temperature for 6 hours by adding 1-iodoalkynes slowly to organostannanes.

A cross-coupling reaction of allyl halides 1 with alkynyltins 3 in the presence of "Ni(PR3)n" (R = Ph, OEt, or OPh) catalyst was carried out in THF at reflux to give 1,4-enynes.The regioselectivity of the coupling of 1f-i with 3a was investigated in the presence of various phosphorus ligands.Interestingly, prenyl (1j) and geranyl chlorides (1k) selectively reacted with 3 at the more-hindered positions of substituted η3-allylnickel intermediates 21 (M = Ni) to yield 23 and 25, respectively.Regioselectivity in these reactions may result from greater steric crowding between the phosphorus ligand and the disubstituted position in 26b than in 26a.In contrast, the palladium-catalyzed reactions of 1j and 1k with 3 selectively gave 22 and 24, respectively.Thus, the steric crowding in a Pd analogue of 26b is less than that in a Ni analogue of 26b, since Pd has a larger covalent radius than Ni.

The reactions of unsaturated episulfides with bromine and iodine have been studied.Initially produced in the reaction is a ring-opened sulfenyl halide intermediate, which in the presence of the carbon-carbon double bond or triple bond cyclizes to β,β'-dihalo sulfide cycloadducts.The regiochemistry and relative stereochemistry of these cyclizations have been examined as a function of the length of the tether between the episulfide and the unsaturated functionality, the presence of alkyl substituents, and the type of unsaturation.A discussion of the mechanistic and stereochemical features of the ring-expansion process is presented.

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Palladium(0) complexes catalyzed a dimerization/allylation of 1-alkynes with allyl carbonate in which three carbon-carbon bonds were formed regio- and stereoselectively.

The reaction of isoxazol-5-ones derived from β-keto esters and hydroxylamine with sodium nitrite and ferrous sulphate in aqueous acetic acid affords the corresponding acetylenes in moderate to good yield. Key Words: Alkynes; Isoxazol-5-ones; β-Keto esters

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The reactions of various types of organic bromides with a mixture of bicycloheptene or bicycloheptadiene and alkynes are reported.The products are bicyclic compounds, containing an organic chain and an alkynyl group in adjacent positions.In the presence o

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