Iridium-catalyzed hydroiodination of functionalized alkynes

The efficiency of an Ir(I)/HI system has been studied. The association of hydroiodic acid with iridium has been tested in the catalytic hydroiodination of alkynes. The use of [Ir(cod)Cl]₂ dimer led to clean hydroiodination reactions and afforded the corresponding vinyliodides as a mixture of derivatives, where the Markovnikov type adduct was found to be the major product (80/20 to 93/7 ratio), in good yields. The mechanism was investigated and two main pathways seemed to be involved, one based on an initial oxidative addition of HI to the Ir(I) complex and the other one based on a π-activation of the alkyne moiety. The corresponding vinyliodides were engaged in Pd-catalyzed cross-coupling (Sonogashira and Suzuki-Miyaura) reactions under organoaqueuous conditions.     

A convenient hydroiodination of alkynes using I2/PPh3/H2O and its application to the one-pot synthesis of trisubstituted alkenes via iodoalkenes using Pd-catalyzed cross-coupling reactions

A facile hydroiodination of alkynes using readily-available reagents such as I₂, PPh₃, and H₂O has been developed. This is extended to the one-pot synthesis of trisubstituted alkenes from alkynes via iodoalkenes using Pd-catalyzed cross-coupling and related methods such as the Suzuki–Miyaura cross-coupling, Sonogashira cross-coupling reaction, and Mizoroki–Heck reaction.     

Regiocontrol in the palladium-catalyzed hydrophosphinylation of terminal alkynes

The regioselectivity of the palladium-catalyzed hydrophosphinylation of terminal alkynes was investigated. Complementary conditions to achieve the predominant formation of either the linear or the branched alkenyl-H-phosphinate products were identified. With Pd/xantphos in acetonitrile, the linear isomer is generally obtained with good to excellent selectivity, and E-stereospecificity. On the other hand, by using Pd/dppf in the non-polar solvent toluene, good selectivity for the branched alkenyl-H-phosphinate is typically observed. The role of various reaction parameters is studied.     

Terminal alkynes from aldehydes via dehydrohalogenation of (Z)-1-iodo-1-alkenes with TBAF

Terminal alkynes were prepared in near quantitative yields via dehydrohalogenation of (Z)-1-iodo-1-alkenes with tetrabutylammonium fluoride (TBAF) under mild conditions. The methodology was expanded to include a one-pot, direct synthesis of terminal alkynes from aldehydes without the necessity of isolating and purifying the intermediate iodoalkene.     

Nickel-catalyzed regioselective hydrocyanation of terminal alkynes by assistance of a tosyl group

Nickel-catalyzed regioselective hydrocyanation of terminal alkynes is described. A tosylamide functionality at the propargyl position was the most suitable group for controlling the regiochemistry for CCN bond formation as well as rate enhancement. A gram-scale synthesis was achieved by minimizing the catalyst loading to 2?mol%. The major HCN adduct could be transformed to the corresponding indoline through construction of a benzylic quaternary carbon under iron catalysis.     

铜催化的端基炔偶联反应的研究进展

综述了近年来应用于端基炔偶联反应的均相、多相铜基催化剂的研究进展,包括Cu(I)、Cu(II)以及CuNPs催化剂。阐述了各催化剂催化端基炔偶联反应的最优条件,从催化剂的寿命、底物适用性等方面比较了各催化剂的性能,以及各类催化剂的可能反应机理。通过比较可得,负载型Cu(II)多相催化剂稳定且制备过程简单易行,反应条件温和、效率高,将可能成为端基炔偶联反应今后发展的主要趋势。     

Highly regioselective palladium/copper-catalysed cross-coupling reactions of terminal alkynes and allenes

The Pd/Cu-catalysed cross-coupling reaction of heterocyclic terminal alkynes and allene/allenyl heterocycles affords novel trisubstituted en-ynes in good yield.     

Highly selective silylformylation of internal and functionalised alkynes with a cationic dirhodium(II) complex catalyst

The tetracationic complex [Rh₂(MeCN)₂(Naft)₄](BF₄)₄ (Naft = μ-1,8-naphthyridine) was found to be an efficient catalyst for the silylformylation of internal and functionalised alkynes to yield useful synthetic intermediates. The complex exhibits an unprecedented chemoselectivity towards alkyne silylformylation instead of simple hydrosilylation, as well as a good stereoselectivity. The catalytic efficiency of the complex is markedly superior compared to that of previously reported catalysts such as [] or Rh₄(CO)₁₂; incidentally, the performance of the latter catalyst was found to vary dramatically with its shelf-life, which indicates that the catalyst evolves with ageing towards other species, most notably higher nuclearity rhodium carbonyl clusters, which are more chemoselective towards silylformylation. Preliminary results on the determination of the catalytically active species in the case of complex [Rh₂(MeCN)₂(Naft)₄](BF₄)₄ indicate that the complex is reduced in situ to a dirhodium(I) species which maintains the dimeric, lantern-shaped structure.     

Iridium complex-catalyzed addition of water and alcohols to non-activated terminal alkynes

The addition of water and alcohols to non-activated terminal alkynes was found to be promoted by an iridium complex combined with Lewis acid and phosphite. Thus, terminal alkynes reacted with water or alcohols to give ketones or ketals, respectively, in good to excellent yields. α,ω-Diyne like 1,7-octadiyne was converted into 1-(2-methyl-cyclopent-1-enyl)ethanone through the intramoleculer aldol condensation of the resulting 2,7-octanedione induced by Lewis acid.     

Ready access to organoiodides: Practical hydroiodination and double-iodination of carbon-carbon unsaturated bonds with I2

By using I₂ or I₂/H₃PO₃ system, various alkenes and alkynes were converted to the corresponding alkyl and alkenyl iodides in good yields. In the presence of I₂, alkynes could be di-iodinated using H₂O as the solvent in air at room temperature. This method also features the simple work-up procedure since the pure product could be obtained by extraction. Additionally, for the first time, combining with the non-toxic and cheap phosphonic acid H₃PO₃, alkenes and alkynes were also hydroiodinated successfully, which provides a simple and practical approach for synthesis of organoiodides.     

Orthopalladacycles derived from α-diphenylhydrazonoketene dithioacetals and their reactivity with terminal alkynes

In this paper, we present the synthesis and characterization of new orthopalladated complexes derived from α-diphenylhydrazonoketene dithioacetals. From their reaction with terminal alkynes, the intermediates of the expected C_sp-C_sp2coupling reaction were isolated in stable form and their structures were confirmed by X-ray diffraction studies.     

Silver-catalyzed regioselective carbomagnesiation of alkynes with alkyl halides and Grignard reagents

A silver-catalyzed carbomagnesiation of alkynes with alkyl halides and Grignard reagents afforded alkenyl Grignard reagents regioselectively, where the alkyl group of the alkyl halide, but not that of the Grignard reagent, was introduced into the alkyne. Application to δ-haloalkylacetylenes yielded cyclopentanes or a tetrahydrofuran containing an exo-methylene substituent via 5-exo-dig cyclization.     

A convenient scalable one-pot conversion of esters and Weinreb amides to terminal alkynes

Esters and amides undergo reduction to the corresponding aldehydes using DIBAL-H followed by same pot conversion to terminal alkynes utilizing the Bestmann-Ohira reagent in good to excellent yields. Additionally chiral nonracemic substrates undergo this transformation with complete preservation of stereochemical integrity.     

Highly regioselective Wittig reactions of cyclic ketones with a stabilized phosphorus ylide under controlled microwave heating

Significant base and temperature effects on the Wittig reactions of cyclohexanones with (carbethoxymethylene)triphenylphosphorane under microwave irradiation were observed. For the Wittig reactions carried out in a domestic microwave oven under solvent-free conditions, the initially formed exo-olefin products isomerized into the thermodynamically more stable endo-olefins due to uncontrolled high reaction temperature. In sharp contrast, under controlled microwave heating, both exo- and endo-olefins have been selectively synthesized by accurately regulating the reaction temperature with or without a base.     

Phosphine-catalyzed regioselective heteroaromatization between activated alkynes and isocyanides leading to pyrroles

The organophosphine catalyzed reaction of activated alkynes with isocyanides produces the corresponding heteroaromatization products, pyrroles, regioselectively in good yields. The reaction proceeds most probably through the 1,4-addition of the nucleophilic phosphine catalyst to the alkynes, followed by a [3+2] cycloaddition between the resulting alkenyl phosphine intermediates and a carbanion derived from the isocyanides.     

Highly enantioselective addition of linear alkyl alkynes to linear aldehydes

It is discovered that the use of biscyclohexylamine (Cy₂NH) as an additive can greatly enhance the enantioselectivity for the reaction of linear alkyl alkynes with linear aldehydes. The combination of (S)-BINOL (20 mol %), Cy₂NH (5 mol %), ZnEt₂ (2 equiv), and Ti(OⁱPr)₄ (0.5 equiv) catalyzes the reaction at room temperature in diethyl ether solution with 81-89% ee and 57-77% yield.     

Stereo- and regioselective gold-catalyzed hydroamination of internal alkynes with dialkylamines

We report the use of a P,N-ligand to support a gold complex as a state-of-the-art precatalyst for the stereoselective hydroamination of internal aryl alkynes with dialkylamines to afford E-enamine products. Substrates featuring a diverse range of functional groups on both the amine (ether, sulfide, N-Boc amine, fluoro, nitrile, nitro, alcohol, N-heterocycles, amide, ester, and carboxylic acid) and alkyne (ether, N-heterocycles, N-phthalimide amines, and silyl ethers) are accommodated with synthetically useful regioselectivity.     

Palladium-catalysed aminocarbonylation of iodoarenes and iodoalkenes with aminophosphonate as N-nucleophile

The high-yielding synthesis of novel N-acyl phosphonates with unprecedented structure was carried out by a homogeneous carbonylation reaction under mild reaction conditions. The palladium-catalysed aminocarbonylation of iodoalkenes (1-iodo-cyclohexene, 1-iodo-4-tert-butyl-cyclohexene, 1-iodo-2-methyl-cyclohexene and α-iodostyrene) with diethyl α-aminobenzyl-phosphonate as N-nucleophile resulted in the exclusive formation of carboxamides. The same reaction with iodoaromatics (iodobenzene, 2-iodothiophene) provided the corresponding carboxamide in high yields and some 2-keto-carboxamides as side products due to single and double carbon monoxide insertion, respectively.     

Highly regioselective hydroaminomethylation of terminal olefins to linear amines using Rh complexes with a Tetrabi phosphorus ligand

A highly regioselective hydroaminomethylation of terminal olefins catalyzed by Rh complexes with 2, 2′, 6, 6′‐tetrakis ((diphenylphosphino)methyl)‐1, 1′‐biphenyl (Tetrabi) ligand has been developed. Up to 99 % amine selectivity, 168 linear/branched amine product ratio (n/i), and 97.4 % linear amine yield has been obtained at a substrate/rhodium precursor ratio (S/Rh) of 1000 with this methodology. The turnover number was achieved 6930 at 10000 S/Rh ratio, and the n/i can reach up to >525. Several different olefins and secondary amines have been applied successfully with high chemoselectivity (99 %), yield (>98 %), and regioselectivity (>120).     

Efficient synthesis of enynes by tetraphosphine-palladium-catalysed reaction of vinyl bromides with terminal alkynes

Through the use of [PdCl(C₃H₅)]₂/cis,cis,cis-1,2,3,4-tetrakis(diphenylphosphinomethyl)cyclopentane as catalyst, a range of vinyl bromides undergoes Sonogashira cross-coupling reaction with a variety of alkynes, leading to the corresponding 1,3-enynes in good yields. The reaction tolerates several alkynes such as phenylacetylene, dec-1-yne, 2-methylbut-1-en-3-yne a range of alk-1-ynols, 3,3-diethoxyprop-1-yne and a propargyl amine. Higher reactions rates were observed in the presence of phenylacetylene, dec-1-yne, but-3-yn-1-ol, pent-4-yn-1-ol, 3,3-diethoxyprop-1-yne or 1,1-dipropyl-2-propynylamine than with propargyl alcohol, 3-methoxy-prop-1-yne or 2-methylbut-1-en-3-yne. This catalyst can be used at low loading even for reactions of sterically hindered vinyl bromides such as bromotriphenylethylene or 2-bromo-3-methyl-but-2-ene.