Palladium-catalyzed cross-coupling reaction of ethynylstibanes with organic halides

Kakusawa, Naoki; Yamaguchi, Kouichiro; Kurita, Jyoji

doi:10.1016/j.jorganchem.2005.03.021

Cited by 59 publications

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“…ethynylstibanes (1) were coupled with acyl chlorides, vinyl iodides and aryl iodides to give ethynylketones, 1,3-enynes, and arylacetylens, respectively. 22,23) We also demonstrated that these reactions were accelerated with microwave irradiation. 24) A mild and efficient Sb(III)-mediated cross-coupling reaction was also achieved with ethynyland ary-1,5-azastibocienes bearing an intramolecular N … Sb non-bonding interaction.…”

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confidence: 74%

“…2,[14][15][16]18,21) For direct cross-coupling reaction of 1 and aryl iodides giving rise to diaryl acetylenes, polar aprotic solvents such as hexamethylphosphramide (HMPA), 1-methyl-2-pyrrolidone (NMP) or amine have been reported to give rather superior result. 23) However, in amine solvents such as morpholine and triethylamine, insertion of CO did not take place smoothly and direct coupled diphenylacetylene (4a) was formed as a main product. When the reaction was performed in N,N-dimethylacetamide (DMA), the expected carbonylated ethynylphenylketone (3a) was obtained in 45% yield and direct coupled product (4a) was reduced to 8% even under 1 atm of CO. Search for a suitable Pd catalyst using DMA as a solvent revealed that phosphine-ligated Pd catalysts were superior to ligandless Pd(OAc) 2 in the present reaction.…”

Section: Resultsmentioning

confidence: 99%

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Carbonylative Cross-Coupling Reaction of Ethynylstibane with Aryl Iodides

Kakusawa

Kurita

2006

CHEMICAL & PHARMACEUTICAL BULLETIN

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Recent remarkable development of novel transmetallating agents for cross-coupling reactions has been fascinating to many synthetic chemists because of its high reliability and wide applicability for C-C, C-O and C-N bond forming reaction.1,2) Especially, investigations on novel coupling agents involving typical heavier elements such as In, 3,4) Si, 5-7) Bi, 8,9) and Ge 10,11) attract much attention not only of heteroatom chemists, but also of synthetic chemists. These transmetallating agents can easily be activated and coupled with various organic halides under mild condition, based on a hypervalent strategy.12,13) One useful application of these transmetallating agents is carbonylative cross-coupling reaction which leads to the formation of unsymmetrical ketones in one-pot operation from an appropriate transmetallating agent and organic halides under carbon monoxide (CO) atmosphere. [14][15][16][17][18][19][20][21] The organoantimony(III) [Sb(III)] compounds are relatively stable and can be prepared easily compared to organoantimony(V) and hypervalent antimony compounds. The facile access of Sb(III) compounds stimulated us to employ them as practical organic reagents. We have recently explored the palladium-catalyzed cross-coupling reaction of Sb(III) compounds with organic halides and their versatile applicability, e.g. ethynylstibanes (1) were coupled with acyl chlorides, vinyl iodides and aryl iodides to give ethynylketones, 1,3-enynes, and arylacetylens, respectively. 22,23) We also demonstrated that these reactions were accelerated with microwave irradiation. 24) A mild and efficient Sb(III)-mediated cross-coupling reaction was also achieved with ethynyland ary-1,5-azastibocienes bearing an intramolecular N … Sb non-bonding interaction. 25,26) As an extension of the versatility of Sb(III) compounds as a transmetallating agent, we investigated the cross-coupling reaction of ethynylstibanes with aryl iodides under CO atmosphere. In the present reaction, the yield of the carbonylated coupling products is sensitive to the nature of the Pd catalyst, and superior results were obtained by using a monodentate phosphine-ligated Pd catalyst. It also appeared that a variety of unsymmetrical ethynyl ketones could be synthesized in excellent yield under high pressure condition (CO, 20 atm) even in the reactions with electron-deficient aryl iodides which usually gave inferior results due to their tendency to undergo decarbonylation. Results and DiscussionPd-Catalyzed Carbonylative Cross-Coupling Reaction of Ethynylstibane with Aryl Iodides under CO Atmosphere In order to optimize the reaction conditions, we initially attempted the reaction of ethynyldiphenylstibane (1) and iodobezene (2a) under atmospheric CO pressure using a variety of solvents in the presence of 5 mol% of various palladium (Pd) catalysts (Table 1). The reaction did not proceed in THF or benzene which was often employed for carbonylative cross-coupling with a variety of organometallic compounds.2,14-16,18,21) For direct cross-coupling reaction of 1 and...

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confidence: 74%

Section: Resultsmentioning

confidence: 99%

Carbonylative Cross-Coupling Reaction of Ethynylstibane with Aryl Iodides

Kakusawa

Kurita

2006

CHEMICAL & PHARMACEUTICAL BULLETIN

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“…In contrast, (E)-3,4-dimethoxy-β-bromostyrene proved to be a less effective coupling partner, probably owing to its electron-rich properties and steric hindrance ( Table 2, Entries 3 and 4). Bromine and chlorine groups are well tolerated on the vinyl bromides (Table 2, Entries 5, 6,11,13). In addition, terminal alkynes with an electron-donating group showed higher reactivity than those with electron-withdrawing groups ( tained during the reaction, and the products were obtained specifically as (E)-enynes.…”

Section: Resultsmentioning

confidence: 99%

“…In this regard, the metal-catalyzed coupling reaction between an alkyne and a structurally defined organometallic alkene (B, [6] Sn, [7] Te , [8] Cu, [9] ) or the alkenylation of alkynylmetals, such as Si [10] and Sb, [11] have been developed to synthesize conjugated enynes in a specific stereoselective manner (Scheme 1, Equations b and c). However, the organometallic substrates are toxic and difficult to prepare.…”

Section: Introductionmentioning

confidence: 99%

Palladium‐Free Synthesis of Conjugated Enynes by Direct Olefination of Terminal Alkynes Using Vinyl Bromides

2009

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“…Thereafter, we also demonstrated that the same reaction of Ph 2 Sb R with Ar-X or vinyl halides proceeded more efficiently in amine solvents, in that Sb · · · N intermolecular coordination would facilitate the coupling reaction. 8,9) Taking these results and knowing that MW irradiation is highly effective for a variety of transition metal-catalyzed reaction into consideration, [10][11][12][13][14][15][16] the reaction of diphenyl(phenylethynyl)stibane 1 with aryl halides 2 was performed under MW irradiation to improve the reaction. In this note we report the results of our investigations on the Pd-catalyzed coupling reaction in the presence of ammonium salts as an aid for effective MW absorption in a polar solvent.…”

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confidence: 99%

Microwave-Assisted Cross-Coupling Reaction of Alkynylstibanes with Aryl Iodides in the Presence of Ammonium Salt

Kakusawa

Kurita

2005

CHEMICAL & PHARMACEUTICAL BULLETIN

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The scope of microwave-assisted coupling reaction of alkynylstibane and aryl iodides to form diarylalkynes is presented. Highly efficient reaction took place smoothly in dimethyl sulfoxide in the presence of cetyltrimethylammonium bromide with much shorter time (1 min) and lower catalyst loading (0.5 mol%) than the conventional method (heating for 24 h with 10 mol% catalyst).Key words microwave; cross-coupling; alkynylstibane; aryl iodide; palladium catalyst; phase transfer catalyst The use of microwave (MW) oven as a new tool for synthetic chemistry is a fast-growing area, and the technique has been accepted as a method for reducing reaction times and for increasing yields of product, as well as for improving selectivity compared to conventional methods.1,2) As a result, this has opened up the possibility of optimizing various reactions in a short time.3-6) We have recently reported that ethynylstibanes (Ph 2 Sb R) resulted in cross-coupling reaction to afford ethynylketones (R COR 1 ) on heating with acyl chlorides (R 1 COCl) in the presence of a Pd catalyst [PdCl 2 (PPh 3 ) 2 ]. 7) However, the ethynylation of aryl halides (Ar-X) proceeded sluggishly under the same reaction conditions; the reaction needs greater loading of the Pd catalyst (10 mol%) and longer reaction time (24 h at 80°C), and the yield of the coupling product (R Ar) is low (16% yield). Thereafter, we also demonstrated that the same reaction of Ph 2 Sb R with Ar-X or vinyl halides proceeded more efficiently in amine solvents, in that Sb · · · N intermolecular coordination would facilitate the coupling reaction. 8,9) Taking these results and knowing that MW irradiation is highly effective for a variety of transition metal-catalyzed reaction into consideration, 10-16) the reaction of diphenyl(phenylethynyl)stibane 1 with aryl halides 2 was performed under MW irradiation to improve the reaction. In this note we report the results of our investigations on the Pd-catalyzed coupling reaction in the presence of ammonium salts as an aid for effective MW absorption in a polar solvent. Under optimal reaction conditions, the reaction took place quite effectively in extremely short time (1 min) to afford the coupling products diarylacetylene 3 along with 1,4-diphenyl-1,3-butadiyne 4 in good yields even when only 0.5 mol% of the palladium catalyst was employed.Initial attempts for the reaction of 1 with iodobenzene 2a in the presence of 5 mol% of PdCl 2 (PPh 3 ) 2 under MW irradiation in 1,2-dichloroethane (DCE) gave cross-coupling product 3a (9%) and homo-coupling product 4 (20%) in low yields. The MW effect is known to be operative in a highly polarized medium, so it is preferable to carried out the reaction in solvents with higher dielectric constant.

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Palladium-catalyzed cross-coupling reaction of ethynylstibanes with organic halides

Cited by 59 publications

References 55 publications

Carbonylative Cross-Coupling Reaction of Ethynylstibane with Aryl Iodides

Carbonylative Cross-Coupling Reaction of Ethynylstibane with Aryl Iodides

Palladium‐Free Synthesis of Conjugated Enynes by Direct Olefination of Terminal Alkynes Using Vinyl Bromides

Microwave-Assisted Cross-Coupling Reaction of Alkynylstibanes with Aryl Iodides in the Presence of Ammonium Salt

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