Synthesis of 1,3-dienes
A broad range of 1,3-dienes have been prepared by the Heck olefination of vinyl bromides using low loadings of [Pd(η3-C3H5)Cl]2/cis,cis,cis-1,2,3,4-tetrakis[(diphenylphosphino)methyl]cyclopentane (Tedicyp) as the catalyst precursor. Both α- and β-substituted vinyl bromides undergo the Heck reaction with nonfunctionalised and functionalised alkenes such as acrylates, enones, styrenes.
M. Lemhadri, A. Battace, F. Berthiol, T. Zair, H. Doucet, M. Santelli, Synthesis, 2008, 1142-1152.
Heck Coupling with Nonactivated Alkenyl Tosylates and Phosphates: Examples of Effective 1,2-Migrations of the Alkenyl Palladium(II) Intermediates
A. L. Hansen, J.-P. Ebran, M. Ahlquist, P.-O. Norrby, T. Skydstrup, Angew. Chem. Int. Ed., 2006, 45, 3349-3353.
A general and mild protocol of oxygen-promoted Pd(II) catalysis allows a selective cross-couplings of alkenyl- and arylboron compounds with various olefins. Unlike most cross-coupling reactions, this new methodology works well even in the absence of bases, consequently averting undesired homo-couplings.
K. S. Yoo, C. H. Yoon, J. W. Jung, J. Am. Chem. Soc., 2006, 128, 16348-16393.
The palladium-catalyzed cross-coupling reaction of air-stable potassium (E)- and (Z)-alkenyltrifluoroborates with either (E)- or (Z)-alkenyl bromides allows a stereoselective synthesis of conjugated dienes in moderate to excellent yields. A variety of functional groups are tolerated in both coupling partners.
G. A. Molander, L. A. Felix, J. Org. Chem., 2005, 70, 3950-3956.
A sequential, palladium-catalyzed, stereoselective disubstitution of 1,1-dibromoalkenes with various alkenyltrifluoroborates followed by alkyltrifluoroborates proceeds smoothly in one pot under mild reaction conditions to provide the corresponding trisubstituted, conjugated dienes in excellent yield.
G. A. Molander, Y. Yokoyama, J. Org. Chem., 2006, 71, 2493-2498.
1-Alkenylboronic acid pinacol esters have been synthesized via a palladium-catalyzed cross-coupling reaction of bis(pinacolato)diboron with 1-alkenyl halides or triflates in toluene at 50°C in the presence of KOPh in high yields with complete retention of configuration of the double bonds. A one-pot synthesis of unsymmetrical 1,3-dienes via the borylation-coupling sequence has been developed.
J. Takagi, K. Takahashi, T. Ishiyama, N. Miyaura, J. Am. Chem. Soc., 2002, 124, 8001-8006.
A variety of organolithiums are added to terminal and 2,2-disubstituted epoxides in the presence of LTMP to generate alkenes in a completely regio- and highly stereoselective manner. Arylated alkenes, dienes, allylsilanes, and enynes are accessed using this procedure.
D. M. Hodgson, M. J. Fleming, S. J. Stanway, J. Org. Chem., 2007, 72, 4763-4773.
The PdCl2/PtBu3 catalytic system with copper(I) iodide and cesium fluoride in DMF is most effective for coupling aryl bromides, while Pd(PPh3)4 is optimal when coupling iodides and triflates. The combination of copper(I) iodide and cesium fluoride should allow the synthesis of sterically hindered systems and promotes electronically disfavored coupling reactions.
S. P. H. Mee, V. Lee, J. E. Baldwin, Angew. Chem. Int. Ed., 2004, 43, 1132-1136.
Exposure of aromatic and aliphatic N-arylsulfonyl aldimines to equal volumes of acetylene and hydrogen gas at 45°C and ambient pressure in the presence of chirally modified cationic rhodium catalysts provides (Z)-dienyl allylic amines in highly optically enriched form and as single geometrical isomers.
E. Skucas, J. R. Kong, M. J. Krische, J. Am. Chem. Soc., 2007, 129, 7242-7243.
Exposure of aldehydes or α-ketoesters to acetylene and hydrogen gas at ambient temperature and pressure in the presence of a cationic rhodium catalysts provides the products of a formal carbonyl Z-butadienylation. These multicomponent couplings represent the first use of acetylene gas in metal-catalyzed reductive C-C bond formation.
J. R. Kong, M. J. Krische, J. Am. Chem. Soc., 2006, 128, 16040-16041.
A cationic rhodium(I)/H8−BINAP complex catalyzes a codimerization of alkenes bearing no α-hydrogen and electron-deficient internal alkynes, leading to 1,3-dienes in good yields with good regio- and stereoselectivity.
Y. Shibata, M. Hirano, K. Tanaka, Org. Lett., 2008, 10, 2829-2831.
A version of a Ru-catalyzed alkene-alkyne coupling process generates 1,3-dienes as the Z,Z-isomer. The scope of this new atom-economic process is described.
B. M. Trost, A. Martos-Redruejo, Org. Lett., 2009, 11, 1071-1074.
The rhodium-catalyzed reaction of aryl boronic acids with internal alkynes and acrylates in water gives the domino coupling products. The reaction demonstrates that water offers the possibility to discover novel transformations.
T. Kurahashi, H. Shinokubo, A. Osuka, Angew. Chem. Int. Ed., 2006, 45, 6336-6338.
N-Vinylpyridinium and -trialkylammonium tetrafluoroborate salts represent a new class of electrophilic coupling partner for Pd(0)-catalyzed Suzuki cross-coupling reactions with various boronic acids in high yields. The crystalline, air-stable, and nonhygroscopic salts are easily prepared from activated acetylenes and pyridinium or trialkylammonium tetrafluoroborates.
K. R. Buszek, N. Brown, Org. Lett., 2007, 9, 707-710.
A stereoselective arylation and vinylation of alkenes without transition-metal catalysts takes place through an interesting NBS-promoted semipinacol rearrangement under mild conditions and a subsequent unusual NaOH-mediated Grob fragmentation.
D.-Y. Yuan, Y.-Q. Tu, C.-A. Fan, J. Org. Chem., 2008, 73, 7797-7799.
A stereoselective approach towards ethyl-substituted conjugated dienoic esters utilising a Suzuki cross-coupling reaction has been achieved. In addition, a method for their conversion into the corresponding ethyl ketones is presented.
D. Keck, T. Muller, S. Bräse, Synlett, 2006, 3457-3460.
Lewis-acid catalysts such as AlMe3, AlMe2Cl, and BPh3 significantly improve the efficiency of the nickel-catalyzed aryl- and alkenylcyanation of alkynes. Electron-rich cyanides, which exhibit poor reactivity in the absence of Lewis acids, readily undergo the arylcyanation reaction under the newly disclosed conditions.
Y. Nakao, A. Yada, S. Ebata, T. Hiyama, J. Am. Chem. Soc., 2007, 129, 2428-2429.
The in situ generated Blaise reaction intermediate, a zinc bromide complex of β-enaminoester, reacts with various alkynes under mild conditions to afford α-vinylated β-enaminoesters in good to excellent yields.
Y. S. Chun, Y. O. Ko, H. Shin, S.-g. Lee, Org. Lett., 2009, 11, 3414-3417.
2-Alkynyl esters are stereo- and regioselectively converted to E-β-chloro-α-iodo-α,β-unsaturated esters by exposure to Bu4NI in refluxing dichloroethane. Single-isomer tetrasubstituted olefins bearing four different carbon substituents are then synthesized by sequential palladium-catalyzed coupling reactions.
A. B. Lemay, K. S. Vulic, W. W. Ogilvie, J. Org. Chem., 2006, 71, 3615-3618.
A novel alkenylative cyclization of enyne was developed using Cp*RuCl(cod) under ethylene gas at room temperature.
M. Mori, N. Saito, D. Tanaka, M. Takimoto, Y. Sato, J. Am. Chem. Soc., 2003, 125, 5606-5607.
A rhodium-catalyzed cycloisomerization converts various acyclic enynes to their cyclic diene isomers with endoselectivity. Two different catalyst systems have been developed, which are effective in promoting the C-C bond-forming cyclization of enynes to furnish carbo- and heterocycles in good to excellent yield. The mechanism is discussed.
H. Kim, C. Lee, J. Am. Chem. Soc., 2005, 127, 10180-10181.
Various arylallenes and alkenylallenes were prepared via coupling of allenylstannanes with aryl iodides or alkenyl iodides in the presence of Pd(PPh3)4 as catalyst, LiCl, and DMF as solvent.
C.-W. Huang, M. Shanmugasundaram, H.-M. Chang, C.-H. Cheng, Tetrahedron, 2003, 59, 3635-3641.
Highly regioselective Heck couplings of α,β-unsaturated tosylate and mesylate derivatives with N-acyl N-vinylamines and vinyl ethers were achieved. This method provides a cheap alternative to similar couplings using a triflate electrophile.
A. L. Hansen, T. Skrydstrup, Org. Lett., 2005, 7, 5585-5587.