Versatile Cross Coupling Methods:
Hiyama Coupling (R-X + R'-SiR''3)
Hiyama-Denmark Coupling (R-X + R-SiMe2OH)
Kumada Coupling (R-X + R'-MgX)
Negishi Coupling (R-X + R'-ZnX)
Stille Coupling (R-X + R'-SnR''3)
Suzuki Coupling (R-X + R'-BY3)
An efficient cobalt-catalyzed alkylation of aromatic Grignard reagents is performed in good yields in the presence of CoCl2/TMEDA (1:1) as catalytic system. Primary and secondary cyclic or acyclic alkyl bromides were used successfully. The reaction tolerates ester, amide, and keto groups, is inexpensive and very easy to carry out on a larger scale.
G. Cahiez, C. Chaboche, C. Duplais, A. Moyeux, Org. Lett., 2009, 11, 277-280.
A slow and regular addition of primary alkyl and aryl Grignard reagent enables a high-yielding copper-catalyzed alkylation with alkyl bromides in the absence of ligands. With secondary and tertiary alkyl Grignard reagents, the presence of benzonitrile as a very simple ligand is sufficent. A copper-catalyzed alkylation of organolithium compounds was also studied.
G. Cahiez, O. Gager, J. Buendia, Synlett, 2010, 299-303.
The use of catalytic amounts of iron(III) fluoride and 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene (SIPr) enables high-yielding cross-coupling reactions of various combinations of aryl chlorides and alkyl Grignard reagents including methylmagnesium bromide.
R. Agata, T. Iwamoto, N. Nakagawa, K. Isozaki, T. Hatakeyama, H. Takaya, M. Nakamura, Synthesis, 2015, 47, 1733-1740.
A simple, efficient and high-yielding iron-catalyzed cross-coupling reaction of various primary, secondary, and tertiary alkyl chlorides with aryl Grignard reagents was achieved by using N-heterocyclic carbene ligands. A wide range of industrially abundant chloroalkanes can be converted, including polychloroalkanes, which are challenging substrates under conventional cross-coupling conditions.
S. K. Ghorai, M. Jin, T. Hatakeyama, M. Nakamura, Org. Lett., 2012, 14, 1066-1069.
The Pd-catalyzed cross-coupling of aryl bromides or triflates with cyclopropylmagnesium bromide in the presence of substoichiometric amounts of zinc bromide produces cyclopropyl arenes in very good yields. The cross-coupling of other alkyl, cycloalkyl, and aryl Grignard reagents with aryl bromides under the same conditions gives the corresponding substituted arenes in good yields.
C. Shu, K. Sidhu, L. Zhang, X.-j. Wang, D. Krishnamurthy, C. H. Senanayake, J. Org. Chem., 2010, 75, 6677-6680.
Alkyl bromides can be coupled with aryl or heteroaryl bromides in excellent yields in the presence of commercially available tris(trimethylsilyl)silane and a metallaphotoredox catalyst. It is hypothesized that a photocatalytically generated silyl radical species can perform halogen-atom abstraction to activate alkyl halides as nucleophilic cross-coupling partners.
P. Zhang, C. Le, D. W. C. MacMillan, J. Am. Chem. Soc., 2016, 138, 8084-8087.
An efficient reaction of unactivated and cheap alkyl chlorides in the presence of indium and LiI provides alkyl indium species, that effectively underwent palladium-catalyzed cross-coupling reactions with aryl halides with wide functional group tolerance.
B.-Z. Chen, M.-L. Zhi, C.-X. Wang, X.-Q. Chu, Z.-L. Shen, T.-P. Loh, Org. Lett., 2018, 20, 1902-1905.
Hypercoordinate silicates represent an improved class of radical precursors for single-electron transmetalation because of their low oxidation potentials and the innocuous byproducts generated upon oxidation. The cross-coupling of secondary and primary ammonium alkylsilicates with (hetero)aryl bromides works in good to excellent yields.
M. Jouffroy, D. N. Primer, G. A. Molander, J. Am. Chem. Soc., 2016, 138, 475-478.
Stereospecific Pd-Catalyzed Cross-Coupling Reactions of Secondary Alkylboron Nucleophiles and Aryl Chlorides
L. Li, S. Zhao, A. Joshi-Pangu, M. Diane, M. R. Biscoe, J. Am. Chem. Soc., 2014, 136, 14027-14030.
Single-electron-mediated alkyl transfer enables a cross-coupling of secondary alkyltrifluoroborates with an array of aryl bromides under mild conditions. The reaction is mediated by an Ir photoredox catalyst and a Ni cross-coupling catalyst.
D. N. Primer, I. Karakaya, J. C. Tellis, G. A. Molander, J. Am. Chem. Soc., 2015, 137, 2195-2198.
OBBD (B-alkyl-9-oxa-10-borabicyclo[3.3.2]decane) derivatives are easily made and can be used for Suzuki-Miyaura couplings under mild aqueous micellar catalysis conditions. Reaction medium recycling exemplifies the synthetic utility of this technology.
N. R. Lee, R. T. H. Linstadt, D. J. Gloisten, F. Gallou, B. H. Lipshutz, Org. Lett., 2018, 20, 2902-2905.
Cross-coupling of redox-active esters (both isolated and derived in situ from carboxylic acids) with organozinc and organomagnesium species using an Fe-based catalyst system originally developed for alkyl halides is scalable and sustainable.
F. Toriyama, J. Cornella, L. Wimmer, T.-G. Chen, D. D. Dixon, G. Creech, P. S. Baran, J. Am. Chem. Soc., 2016, 138, 11132-11135.
In a decarboxylative coupling of alkyl N-hydroxyphthalimide esters with aryl iodides in the presence of a nickel catalyst and Zn as reducing agent, no photocatalyst, light, or arylmetal reagent is needed to form alkyl radicals from the carboxylic acid derivative. Methyl, primary, and secondary alkyl groups can all be coupled in good yield.
K. M. M. Huihui, J. A. Caputo, Z. Melchor, A. M. Olivares, A. M. Spiewak, K. A. Johnson, T. A. DiBenedetto, S. Kim, L. K. G. Ackerman, D. J. Weix, J. Am. Chem. Soc., 2016, 138, 5016-5019.
A Concise and Atom-Economical Suzuki-Miyaura Coupling Reaction Using Unactivated Trialkyl- and Triarylboranes with Aryl Halides
H. Li, Y.-L. Zhong, C.-y. Chen, A. E. Ferraro, D. Wang, Org. Lett., 2015, 17, 3616-3619.
Zn-Mediated, Pd-Catalyzed Cross-Couplings in Water at Room Temperature Without Prior Formation of Organozinc Reagents
A. Krasovskiy, C. Duplais, B. H. Lipshutz, J. Am. Chem. Soc., 2009, 131, 15592-15593.
Palladium complexes derived from air-stable secondary phosphine oxides or chlorides enabled challenging Kumada-Corriu cross-couplings of unactivated alkyl chlorides bearing β-hydrogens and proved applicable to transformations of alkyl-substituted organometallics.
L. Ackermann, A. R. Kapdi, C. Schulzke, Org. Lett., 2010, 12, 2298-2301.
A room-temperature Ni-catalyzed reductive coupling of aryl bromides with secondary alkyl bromides provides products in good to excellent yields. Slight modification of this protocol allows efficient coupling of activated aryl chlorides with cyclohexyl bromide and aryl bromides with allylic acetate.
S. Wang, Q. Qian, H. Gong, Org. Lett., 2012, 14, 3352-3355.
In the presence of a Ni catalyst and Zn, various aryl and vinyl bromides are reductively coupled with alkyl bromides in high yields. Under similar conditions, activated aryl chlorides can also be coupled with bromoalkanes. The protocols are highly functional-group tolerant, and the reactions are assembled on the benchtop with no special precautions to exclude air or moisture.
D. A. Everson, B. A. Jones, D. J. Weix, J. Am. Chem. Soc., 2012, 134, 6146-6159.
An efficient, nickel-catalyzed direct reductive cross-coupling of equimolar amounts of alkyl halides with aryl halides in the presence of manganese is generally high-yielding, highly functional-group-tolerant, and easy to perform. The reaction appears to avoid the formation of intermediate organomanganese species, and a synergistic effect was found when a mixture of two ligands was employed.
D. A. Everson, R. Shrestha, D. J. Weix, J. Am. Chem. Soc., 2010, 132, 920-921.
An operationally simple cross-coupling reaction between aryl halides and alkyl halides with high selectivity utilizes CoCl2/Me4-DACH as a catalyst system. The underlying domino process exhibits high sustainability as it obviates the need for the pre-formation and handling of stoichiometric amounts of hazardous Grignard compounds.
W. M. Czaplik, M. Mayer, A. J. von Wangelin, Synlett, 2009, 2931-2934.
The alkylation of aryl sulfamates and carbamates using iron catalysis provides synthetically useful yields across a range of substrates. The directing group ability of sulfamates and carbamates, accompanied by their low reactivity toward conventional cross-couplings, renders these substrates useful for the synthesis of polyfunctionalized arenes.
A. L. Silberstein, S. D. Ramgren, N. K. Garg, Org. Lett., 2012, 14, 3796-3799.
Simple, cheap, and toxicologically benign iron salts turned out to be highly efficient precatalysts for cross-coupling reactions of alkyl or aryl Grignard reagents, zincates, or organomanganese species with aryl and heteroaryl chlorides, triflates, and even tosylates. Aryl bromides and iodides are prone to a reduction of their C-X bonds in the presence of the iron catalyst. The exceptionally mild reaction conditions tolerate a series of functional groups such as esters, ethers, nitriles, sulfonates, sulfonamides, thioethers, acetals, alkynes, and -CF3 groups.
A. Fuerstner, A. Leitner, M. Méndez, H. Krause, J. Am. Chem. Soc., 2002, 124, 13856-13863.
Various types of substrates were found to undergo effective cross-coupling with Grignard reagents in the presence of a low-valent iron complex within minutes even at -20°C.
R. Martin, A. Fuerstner, Angew. Chem. Int. Ed., 2004, 43, 3955-3957.
Butylmethylimidazolium tetrachloroferrate (bmim-FeCl4) was found to be a very effective and completely air stable catalyst for the biphasic Grignard cross-coupling with primary and secondary alkyl halides bearing α-hydrogens. The product was simply isolated in the ethereal layer and the ionic liquid catalyst was successfully recycled four times.
K. Bica, P. Gaertner, Org. Lett., 2006, 8, 733-735.
An iron-catalyzed cross-coupling reaction of a primary or secondary alkyl halide with an aryl Grignard reagent proceeds under mild conditions to give the corresponding coupled product in excellent yield.
M. Nakamura, K. Matsuo, S. Ito, E. Nakamura, J. Am. Chem. Soc., 2004, 126, 3686-3687.
Iron-catalyzed cross-coupling of primary and secondary alkyl sulfonates with arylzinc reagents, prepared from the corresponding aryllithium or magnesium reagents with ZnI2, proceeds smoothly in the presence of excess TMEDA and a concomitant magnesium salt.
S. Ito, Y.-i. Fujiwara, E. Nakamura, M. Nakamura, Org. Lett., 2009, 11, 4306-4309.
A Ni-catalyzed process for the cross-coupling of tertiary alkyl nucleophiles and aryl bromides is extremely general for a wide range of electrophiles and generally occurs with little isomerization. The same procedure also accommodates the use of aryl triflates, vinyl chlorides, and vinyl bromides as the electrophilic component.
A. Joshi-Pangu, C.-Y. Wang, M. R. Biscoe, J. Am. Chem. Soc., 2011, 133, 8478-8481.
Suzuki cross-coupling reactions of an unprecedented array of unactivated primary and secondary alkyl halides with arylboronic acids can be accomplished through the use of nickel/amino alcohol-based catalysts. Both the nickel precatalysts and the amino alcohols are commcercially available and air-stable.
F. González-Bobes, G. C. Fu, J. Am. Chem. Soc., 2006, 128, 5360-5361.
Palladium-catalyzed Negishi cross-coupling involving primary and secondary alkyls, even in the presence of β-H, can be achieved using chelating phosphine ligands containing an electron-deficient olefin. The superior effects of the ligands were shown not only in the desired cross-coupling product yields but also in the fast reaction at mild conditions.
X. Luo, H. Zhang, H. Duan, Q. Liu, L. Zhu, T. Zhang, A. Lei, Org. Lett., 2007, 9, 4571-4574.
A CoCl2ˇ2LiCl-catalyzed cross-coupling of diarylmanganese reagents with secondary alkyl iodides provides the cross-coupling products in good yield without rearrangements to unbranched products. High diastereoselectivities can be reached.
M. S. Hofmayer, J. M. Hammann, D. Haas, P. Knochel, Org. Lett., 2016, 18, 6456-6459.
In the presence of a chiral monodentate taddol-derived phosphoramidite ligand, catalytic enantiotopic-group-selective cross-couplings of achiral geminal bis(pinacolboronates) provide a route for the construction of nonracemic chiral organoboronates with high levels of asymmetric induction. Mechanistic experiments suggest that the reaction occurs by a stereochemistry-determining transmetalation with inversion of configuration at carbon.
C. Sun, B. Potter, J. P. Morken, J. Am. Chem. Soc., 2014, 136, 6534-6537.
The use of [PdCl(C3H5)]2/cis,cis,cis-1,2,3,4-tetrakis(diphenylphosphinomethyl)cyclopentane as a catalyst allows the Suzuki coupling of a range of aryl bromides and chlorides with alkylboronic acids in good yields. The functional group tolerance on the aryl halide is remarkable. Furthermore, this catalyst can be used at low loading, even for reactions of sterically hindered aryl bromides.
I. Kondolff, H. Doucet, M. Santelli, Tetrahedron, 2004, 60, 3813-3818.
A novel method for the palladium-catalyzed cross-coupling of alkyl chlorides and Grignard reagents has been developed. Good to excellent yields of the coupling products were obtained at room temperature, and functional groups such as ethers, esters, acetals, fluorides, nitriles, aryl and benzyl were tolerated.
A. C. Frisch, N. Shaikh, A. Zapf, M. Beller, Angew. Chem. Int. Ed., 2002, 41, 4056-4059.
Screening of a 15-member library of phosphaadamantane ligands has allowed for the rapid determination of the most suitable ligand for facilitating Suzuki-type couplings of alkyl halides or tosylates containing β-hydrogens with either boronic acids or alkylboranes.
T. Brenstrum, D. A. Gerristma, G. M. Adjabeng, C. S. Frampton, J. Britten, A. J. Robertson, J. McNulty, A. Capretta, J. Org. Chem., 2004, 69, 7635-7639.
A versatile method has been developed for the cross-coupling of boronic acids with unactivated alkyl electrophiles at room temperature. It has been demonstrated that Pd(P(t-Bu)2Me)2 undergoes oxidative addition under surprisingly mild conditions and that the resulting adduct is sufficiently stable toward β-hydride elimination.
J. H. Kirchhoff, M. R. Netherton, I. D. Hill, G. C. Fu, J. Am. Chem. Soc., 2002, 124, 13662-13663.
A combination of nickel(II) acetylacetonate and (Z)-3,3-dimethyl-1,2-bis(diphenylphosphino)but-1-ene catalyzes cross-coupling reactions of alkyl aryl sulfides and alkenyl alkyl sulfides with primary and secondary alkyl Grignard reagents.
S. Kanemura, A. Kondoh, H. Yorimitsu, K. Oshima, Synthesis, 2008, 2659-2660.
The superacid-catalyzed reaction of various olefinic amines and related compounds with benzene gives addition products in good yields. The formation of reactive, dicationic electrophiles is proposed.
Y. Zhang, A. McElrea, G. V. Sanchez, Jr., D. Do, A. Gomez, S. L . Aguirre, R. Rendy, D. A. Klumpp, J. Org. Chem., 2003, 68, 5119-5122.
Palladium catalyzed Suzuki-Miyaura coupling with aryl chlorides using a bulky phenanthryl N-heterocyclic carbene ligand
C. Song, Y. Ma, Q. Chai, C. Ma, W. Jiang, M. B. Andrus, Tetrahedron, 2005, 61, 7438-7446.
Aryl bromides (4 eq.) were coupled efficiently with organotin (1 eq.) using the tetra(triphenylphosphine)palladium/polyethylene glycol 400 catalytic system in the presence of sodium acetate as base at 100°C, providing excellent yields of the corresponding substituted aryls in short reaction times.
H. Huang, H. Jiang, K. Chen, H. Liu, J. Org. Chem., 2009, 74, 5599-5602.
A readily available nickel/bis(oxazoline) catalyst effectively distinguishes between a CF3 and an alkyl group and accomplishes a wide array of enantioconvergent cross-couplings of arylzinc reagents with CF3-substituted racemic secondary alkyl halides. This method can also be applied without modification to the asymmetric synthesis of other families of fluorinated organic compounds.
Y. Liang, G. C. Fu, J. Am. Chem. Soc., 2015, 137, 9523-9526.
A nickel-catalyzed cross-coupling between arylboronic acids and unactived 1-fluoro-1-iodoalkanes offers high efficiency, mild conditions, and excellent functional-group compatibility. Readily available nitrogen and phosphine ligands generated a variety of easily tunable catalysts to promote the fluoroalkylation for a broad range of both coupling partners.
J. Sheng, H.-Q. Ni, G. Liu, Y. Li, X.-S. Wang, Org. Lett., 2017, 19, 4440-4443.
Microscale parallel experimentation was used to discover catalyst systems capable of coupling secondary organotrifluoroborates with aryl chlorides and bromides. A ligand-dependent β-hydride elimination/reinsertion mechanism was implicated in the cross-coupling of more hindered substrates, leading to isomeric mixtures of coupled products in some cases.
S. D. Dreher, P. G. Dormer, D. L. Sandrock, G. A. Molander, J. Am. Chem. Soc., 2008, 130, 9257-9259.
Suitable conditions enable the Suzuki-Miyaura coupling reaction of potassium cyclopropyl- and cyclobutyltrifluoroborates in moderate to excellent yield with electron-rich, electron-poor, and hindered aryl chlorides to give various substituted aryl cyclopropanes and cyclobutanes.
G. A. Molander, P. E. Gormisky, J. Org. Chem., 2008, 73, 7481-7485.
The palladium-catalyzed cross-coupling reaction of tricyclopropylbismuth with aryl and heterocyclic halides and triflates tolerates numerous functional groups and does not require anhydrous conditions. The method was successfully extended to the cross-coupling of triethylbismuth.
A. Gagnon, M. Duplessis, P. Alsabeh, F. Barabé, J. Org. Chem., 2008, 73, 3452-3459.
Using commercially available Ph3PAuCl and readily prepared, benign arylsilanes, a gold-catalyzed oxyarylation of alkenes proceeds smoothly in air. The oxidant, Selectfluor, not only facilitates entry to the Au(I/III) manifold but also provides a fluoride anion for silane activation, thereby avoiding the need for addition of a stoichiometric base.
L. T. Ball, M. Green G. C. Lloyd-Jones, C. A. Russel, Org. Lett., 2010, 12, 4724-4727.
A well-defined cationic Ru-H complex catalyzes the dehydrative C-H alkylation reaction of phenols with alcohols to form ortho-substituted phenol products. The reaction with diols delivers benzofuran derivatives via dehydrative C-H alkenylation and annulation reaction. The catalytic C–H coupling method employs cheap starting materials, exhibits a broad substrate scope, and liberates water as the only byproduct.
D.-H. Lee, K.-H. Kwon, C. S. Yi, J. Am. Chem. Soc., 2012, 134, 6571-6574.
Kinetic vs thermodynamic deprotonation studies on secondary and tertiary sulfonamides using n-BuLi have been carried out. Application of the developed conditions allows the synthesis of diverse sulfonamide products (E=Me).
S. L. MacNeil, O. B. Familoni, V. Snieckus, J. Org. Chem, 2001, 66, 3662-3670.
By treatment with s-BuLi/TMEDA at -78°C, unprotected 2-methoxybenzoic acid is deprotonated exclusively in the position ortho to the carboxylate. A reversal of regioselectivity is observed when the acid is treated with n-BuLi/t-BuOK.
T.-H. Nguyen, A.-S. Castanet, J. Mortier, Org. Lett., 2006, 8, 765-768.
The mild cross-coupling reaction of alkyl- and arylmanganese reagents with o-chloro- or o-bromoaryl ketones gives substituted ketones in high yields with excellent chemoselectivity.
G. Cahiez, D. Luart, F. Lecomte, Org. Lett., 2004, 6, 4395-4398.
The Rh-catalyzed cross-coupling between ArZnI and TMSCH2I gave various functionalized benzylsilanes in good yields. A mechanism is proposed.
H. Takahashi, K. M. Hossain, Y. Nishihara, T. Shibata, K. Takagi, J. Org. Chem., 2006, 71, 671-675.
An efficient method of constructing 4-benzyl piperidines and related substances is described. This protocol tolerates a wide variation in both reaction partners. The concise formation of a variety of building blocks, such as those described here, has found wide applicability in our drug discovery programs.
S. Vice, T. Bara, A. Bauer, C. A. Evans, J. Fort, H. Josien, S. McCombie, M. Miller, D. Nazzareno, A. Palani, J. Tagat, J. Org. Chem, 2001, 66, 2487-2492.
A bipyridine-ligated nickel mediates the addition of functionalized aryl halides, a vinyl halide, and a vinyl triflate to epoxides under reducing conditions. For terminal epoxides, the regioselectivity of the reaction depends upon the cocatalyst employed. Iodide cocatalysis results in opening at the less hindered position via an iodohydrin intermediate. Titanocene cocatalysis results in opening at the more hindered position.
Y. Zhao, D. J. Weix, J. Am. Chem. Soc., 2014, 136, 48-51.
A highly efficient Pd-catalyzed arylative ring expansion of cyclobutanols with aryl chlorides via C-C bond cleavage at low catalyst loadings tolerates a wide range of functional groups and substitution patterns, thus constituting a straightforward alternative for preparing rather elusive γ-arylated ketones.
A. Ziadi, R. Martin, Org. Lett., 2012, 14, 1266-1269.
A general, highly selective asymmetric redox-relay oxidative Heck reaction using achiral or racemic acyclic alkenols and boronic acids delivers remotely functionalized arylated carbonyl products, with excellent enantioselectivity under mild conditions, bearing a range of useful functionality. The regioselectivity of the initial migratory insertion depends on the electronic nature of the boronic acid.
T.-S. Mei, E. W. Werner, A. J. Burckle, M. S. Sigman, J. Am. Chem. Soc., 2013, 135, 6830-6833.
The catalytic iridium-catalyzed 1,6-addition of aryl boronic acids to electron-deficient dienes gave high yields of the corresponding δ-arylated carbonyl compounds with perfect 1,6-selectivity.
T. Nishimura, Y. Yasuhara, T. Hayashi, Angew. Chem. Int. Ed., 2006, 45, 5164-5166.
An iridium/chiral diene complex enabled a catalytic, asymmetric 1,6-addition of arylboroxines to α,β,γ,δ-unsaturated carbonyl compounds to give δ-arylated carbonyl compounds in high yields with excellent enantioselectivity.
T. Nishimura, Y. Yashuhara, T. Sawano, T. Hayashi, J. Am. Chem. Soc., 2010, 132, 7872-7873.
The superacid-catalyzed (triflic acid) reaction of olefinic amines and related compounds with benzene gives addition products in good yields. A reactive, dicationic species is reported.
Y. Zhang, A. McElrea, G. V. Sanchez, D. Do, A. Gomez, S. L . Aguirre, R. Rendy, D. A. Klumpp, J. Org. Chem., 2003, 68, 5119-5122.
Superelectrophilic reactivity of α,β-unsaturated amides towards weak nucleophiles such as arenes and cyclohexane is initiated either with triflic acid or with excess AlCl3. Condensation with aromatics in the presence of AlCl3 gives 3-arylpropionamides in excellent yields, while a selective ionic hydrogenation of some amides with cyclohexane gives saturated amides.
K. Y. Koltunov, S. Walspurger, J. Sommer, Eur. J. Org. Chem., 2004, 4039-4047.
N-heterocyclic carbene (NHC) ligands efficiently promote a palladium-catalyzed stereospecific and regioselective cross-coupling of enantiopure 2-arylaziridines with arylboronic acids under mild conditions without β-hydride elimination to construct a tertiary stereogenic center.
Y. Takeda, Y. Ikeda, A. Kuroda, S. Tanaka, S. Minataka, J. Am. Chem. Soc., 2014, 136, 8544-8547.
Potassium trifluoro(organo)borates, which are highly stable and easily prepared organoboron derivatives, were able to react with various dehydroamino esters to alanine derivatives in good to high yields. This reaction, catalyzed by rhodium complexes, tolerates a great variety of amino protecting groups.
L. Navarre, S. Darses, J.-P. Genet, Eur. J. Org. Chem., 2004, 69-73.
Rhodium-catalyzed conjugate addition of potassium trifluoro(organo)borates to dehydroalanine derivatives, using chiral ligands such as fluorophos and in situ enantioselective protonation with guaiacol (2-methoxyphenol), afforded a variety of protected α-amino esters with high yields and enantiomeric excesses up to 95%.
L. Navarre, R. Martinez, J.-P. Genet, S. Darses, J. Am. Chem. Soc., 2008, 130, 6159-6169.
A new approach to 2-(arylmethyl)aldehydes begins with a silylformylation reaction of terminal acetylenes with aryl- or heteroarylsilanes, followed by treatment of the products with TBAF to induce a 1,2-anionotropic rearrangement of the aryl group.
L. A. Aronica, P. Raffa, A. M. Caporusso, P. Salvadori, J. Org. Chem., 2003, 5, 9292-9298.
A new, stereoselective, palladium-catalyzed method for the synthesis of substituted tetrahydrofurans from γ-hydroxy alkenes and aryl bromides forms both a C-C and a C-O bond with diastereoselectivities of up to >20:1. The reactions probably proceed via the intramolecular insertion of an olefin into a Pd(Ar)(OR) intermediate.
J. P. Wolfe, M. A. Rossi, J. Am. Chem. Soc., 2004, 126, 1620-1621.
The Rh-catalyzed reaction of 9-aryl-9-borabicyclo[3.3.1]nonanes with α,β-unsaturated ketones and aldehydes gave high yields of tandem 1,4-addition-aldol reaction products with high syn selectivity. The mechanism is discussed.
K. Yoshida, M. Ogasawara, T. Hayashi, J. Am. Chem. Soc., 2002, 124, 10984-10985.
The use of a H8-BINOL-based phosphoramidite ligand enables a Pd-catalyzed highly enantioselective three-component coupling of 1,3-dienes with aryl iodines and sodium dialkyl malonates via a Pd-catalyzed cascade arylation and asymmetric allylic alkylation reaction. This reaction provides an efficient strategy for the enantioselective 1,2-difunctionalization of 1,3-dienes.
X. Wu, H.-C. Lin, M.-L. Li, L.-L. Li, Z.-Y. Han, L.-Z. Gong, J. Am. Chem. Soc., 2015, 137, 13467-13479.
The use of an equimolar amount of base with a diborylmethane enabled a chemoselective Pd-catalyzed Suzuki–Miyaura cross-coupling reaction for the synthesis of various benzylboronate derivatives in very good yields. Reactions of sterically hindered aryl bromides can give products in good yields.
K. Endo, T. Ohkubo, T. Shibata, Org. Lett., 2011, 13, 3368-3371.
Catalytic enantioselective conjunctive cross-couplings that employ Grignard reagents provide chiral organoboronic esters in an efficient and highly selective fashion. The use of sodium triflate enables "ate" complex formation and overcomes catalytic inhibition by halide ions.
G. J. Lovinger, M. D. Aparece, J. P. Morken, J. Am. Chem. Soc., 2017, 139, 3153-3160.
An efficient synthesis of 9H-fluorene derivatives through a Pd(0)-catalyzed cross-coupling reaction of 1,1-diboronates with 2,2′-dibromobiphenyls offers high yields, operational simplicity, and mild reaction conditions.
S. Xu, X. Shangguan, H. Li, Y. Zhang, J. Wang, J. Org. Chem., 2015, 80, 7779-7784.