Categories: C-H Bond Formation >
Reduction of Alkenes
In situ preparation of an active Pd/C catalyst from Pd(OAc)2 and charcoal in methanol enables a simple, highly reproducible protocol for the hydrogenation of alkenes and alkynes and for the hydrogenolysis of O-benzyl ethers. Mild reaction conditions and low catalyst loadings, as well as the absence of contamination of the product by palladium residues, make this a sustainable, useful process.
F.-X. Felpin, E. Fouquet, Chem. Eur. J., 2010, 12440-12445.
The use of hydrogen micro and nanobubbles (MNBs) enables an autoclave-free, gas-liquid-solid multiphase hydrogenation of carbon-carbon unsaturated bonds, in which a high concentration of hydrogen gas is maintained in the liquid phase.
N. Mase, S. Isomura, M. Toda, N. Watanabe, Synlett, 2013, 24, 2225-2228.
A Pd/C-catalyzed hydrogenation using diphenylsulfide as a catalyst poison selectively reduces olefin and acetylene functionalities without hydrogenolysis of aromatic carbonyls and halogens, benzyl esters, and N-Cbz protective groups.
A. Mori, Y. Miyakawa, E. Ohashi, T. Haga, T. Maegawa, H. Sajiki, Org. Lett., 2006, 8, 3279-3281.
Pd/P(t-Bu)3 is an efficient and mild catalyst for selective reduction of various alkenes under transfer-hydrogenation conditions leading to the corresponding saturated derivatives in good yields.
J. M. Brunel, Synlett, 2007, 330-332.
A palladium-fibroin complex catalyzed the chemoselective hydrogenation of acetylenes, olefins and azides in the presence of aromatic ketones and aldehydes, halides, N-Cbz protective groups and benzyl esters which are readily hydrogenated using Pd/C or Pd/C(en) as a catalyst.
T. Ikawa, H. Sajiki, K. Hirota, Tetrahedron, 2005, 61, 2217-2231.
A generally applicable method for the introduction of gaseous hydrogen into a sealed reaction system under microwave irradiation allows the hydrogenation of various substrates in short reaction times with moderate temperatures between 80 °C and 100 °C with 50 psi of hydrogen.
G. S. Vanier, Synlett, 2007, 131-135.
A Pd-catalyzed reaction of water with a diboron compound as the reductant produces clean hydrogen gas under ambient reaction conditions. The B2Pin2-H2O system enables a selective hydrogenation of olefins in the presence of a palladium catalyst.
D. P. Ojha, K. Gadde, K. R. Prabhu, Org. Lett., 2016, 18, 5062-5065.
Diboron reagents efficiently mediate the transfer of H or D atoms from water directly onto unsaturated C-C bonds using a palladium catalyst. This reaction is conducted on a broad variety of alkenes and alkynes at ambient temperature, and boric acid is the sole byproduct.
S. P. Cummings, T.-N. Le, G. E. Fernandez, L. G. Quiambao, B. J. Stokes, J. Am. Chem. Soc., 2016, 138, 6107-6110.
Various carbon-carbon double bonds in olefins and α,β-unsaturated ketones were effectively reduced to the corresponding alkanes and saturated ketones, using ammonium formate as a hydrogen transfer agent in the presence of Pd/C as catalyst in refluxing methanol.
Z. Paryzek, H. Koenig, B. Tabacka, Synthesis, 2003, 2023-2026.
A new recyclable catalyst composed of palladium nanoparticles dispersed in an organic polymer was synthesized by a simple procedure from readily available reagents. This catalyst is robust, and highly active in many organic transformations including alkene and alkyne hydrogenation, carbon-carbon cross-coupling reactions, and aerobic alcohol oxidation.
C. M. Park, M. S. Kwon, J. Park, Synthesis, 2006, 3790-3794.
In a simple continuous hydrogenation of alkenes and alkynes, that requires neither H2 nor metal catalysis, diimide is generated in situ by a novel reagent combination. A simple flow reactor employed minimizes residence time and enables safe operation at elevated temperature.
A. S. Kleinke, T. F. Jamison, Org. Lett., 2013, 15, 710-713.
A one-pot, three-step strategy for the regioselective semihydrogenation of dienes uses 9-BBN-H as a temporary protective group for alkenes. Yields range from 55% to 95%, and the reaction tolerates various common functional groups. Additionally, the final elimination step of the sequence can be replaced with a peroxide-mediated alkylborane oxidation, generating regioselectively alcohols.
T. J. A. Graham, T. H. Poole, C. N. Reese, B. C. Goess, J. Org. Chem., 2011, 76, 4132-4138.
In situ generation of molecular hydrogen by addition of triethylsilane to palladium on charcoal results in rapid and efficient reduction of multiple bonds, azides, imines, and nitro groups, as well as deprotection of benzyl and allyl groups under mild, neutral conditions.
P. K. Mandal, J. S. McMurray, J. Org. Chem., 2007, 72, 6599-6601.
Poly(ethylene glycol) (PEG) (400) has been found to be a superior solvent over ionic liquids by severalfold in promoting the hydrogenation of various functional groups using Adams' catalyst. Both the catalyst and PEG were recycled efficiently over 10 runs without loss of activity, and without substrate cross contamination.
S. Chandrasekhar, S. Y. Prakash, C. L. Rao, J. Org. Chem., 2006, 71, 2196-2199.
A one-pot protocol for the formation of 2-nitrobenzenesulfonylhydrazide (NBSH) from commercial reagents and subsequent alkene reduction is operationally simple and generally efficient. A range of 16 substrates have been reduced, highlighting the unique chemoselectivity of diimide as a alkene reduction system.
B. J. Marsh, D. R. Carbery, J. Org. Chem., 2009, 74, 3186-3188.
Various olefins can be hydrogenated quantitatively with neutral, flavin-derived catalysts in the presence of hydrazine under an athomspheric pressure of O2. A vitamin B2 derivative acts as a highly efficient and robust catalyst for the environmentally benign process producing water and nitrogen gas as the only waste products.
Y. Imada, T. Kitagawa, T. Ohno, H. Iida, T. Naota, Org. Lett., 2010, 12, 32-35.
Olefins can be hydrogenated by treatment with hydrazine in the presence of a 5-ethyl-3-methyllumiflavinium perchlorate catalyst under O2 atmosphere to give the corresponding hydrogenated products in excellent yields along with environmentally benign water and molecular nitrogen as the only waste products.
Y. Imada, H. Iida, T. Naota, J. Am. Chem. Soc., 2005, 127, 14544-14545.
A microwave-assisted, palladium-catalyzed catalytic transfer hydrogenation of different homo- or heteronuclear organic compounds using formate salts as a hydrogen source was performed in ([bmim][PF6]. Essentially pure products could be isolated in moderate to excellent yields by simple liquid-liquid extraction.
H. Berthold, T. Schotten, H. Hönig, Synthesis, 2002, 1607-1610.
The preparation of alkenyl halides of any length from inexpensive starting reagents is reported. Standard organic transformations were used to prepare straight-chain α-olefin halides in excellent overall yields with no detectable olefin isomerization and full recovery of any unreacted starting material.
T. W. Baughman, J. C. Sworen, K. B. Wagener, Tetrahedron, 2004, 60, 10943-10948.
Nanopalladium particles supported on a amphiphilic polystyrene-poly(ethylene glycol) resin catalyzed hydrogenation of olefins and hydrodechlorination of chloroarenes under aqueous conditions.
R. Nakao, H. Rhee, Y. Uozumi, Org. Lett., 2005, 7, 163-165.
Reduction of stilbenes with Na metal in dry THF allowed easy access to various 1,2-diaryl-1,2-disodiumethanes. These diorganometallic intermediates gave 1,2-diarylethanes upon aqueous work up, or trans-1,2-diaryl-substituted cyclopentanes by cycloalkylation with 1,3-dichloropropanes.
U. Azzena, G. Dettori, C. Lubinu, A. Mannu, L. Pisano, Tetrahedron, 2005, 61, 8663-8668.
In a highly enantioselective cobalt-catalyzed hydrogenation of 1,1-diarylethenes at ambient conditions with a bench-stable chiral oxazoline iminopyridine-cobalt complex as precatalyst, a unique o-chloride effect achieves high enantioselectivity. Easy removal as well as further transformations of the chloro group make this protocol a potentially useful alternative to synthesize various chiral 1,1-diarylethanes.
J. Chen, C. Chen, C. Ji, Z. Lu, Org. Lett., 2016, 18, 1594-1597.
A catalytic system of cobalt(II) chloride and diisopropylamine in combination with NaBH4 showed excellent activity in the chemoselective reduction of various carboxylic esters to their corresponding alcohols in very good yields under mild conditions. Unsaturated carboxylic esters give saturated alcohols in high yields.
A. R. Jagdale, A. S. Paraskar, A. Sudalai, Synthesis, 2009, 660-664.
Ammonia, pyridine and ammonium acetate were extremely effective as inhibitors of Pd/C catalyzed benzyl ether hydrogenolysis. While olefin, Cbz, benzyl ester and azide functionalities were hydrogenated smoothly, benzyl ethers were not cleaved.
H. Sajiki, Tetrahedron Lett., 1995, 36, 3465-3468.
Selective hydrogenation conditions of olefin, benzyl ether and acetylene functionalities in the presence of TBDMS or TES ether have been developed.
H. Sajiki, T. Ikawa, K. Hattori, K. Hirota, Chem. Commun., 2003, 654-655.
A highly efficient and highly enantioselective Hantzsch ester mediated conjugate transfer hydrogenation of β,β-disubstituted nitroolefins is catalyzed by a Jacobsen-type thiourea catalyst.
N. J. A. Martin, L. Ozores, B. List, J. Am. Chem. Soc., 2007, 129, 8976-8977.
A highly efficient and enantioselective Hantzsch ester mediated conjugate reduction of β-nitroacrylates is catalyzed by a Jacobsen thiourea catalyst. The reaction is a key step in a new route to optically active β2-amino acids.
N. J. A. Martin, X. Chen, B. List, J. Am. Chem. Soc., 2008, 130, 13862-13863.
A chiral bisphosphine-thiourea ligand was applied in the highly enantioselective hydrogenation of β,β-disubstituted nitroalkenes. The thiourea group of the ligand takes on an important role in this catalytic system as a H-bond donor.
Q. Zhao, S. Li, K. Huang, R. Wang, X. Zhang, Org. Lett., 2013, 15, 4014-4017.
A mild catalytic asymmetric transfer hydrogenation of β,β-disubstituted nitroalkenes using formic acid as reductant in combination with an Ir catalyst is conducted in water at low pH and open to air to give products in good yield and selectivity.
O. Soltani, M. A. Ariger, E. M. Carreira, Org. Lett., 2009, 11, 4196-4198.
An inert, rigid chiral-at-metal iridium(III) complex enables a highly efficient catalytic asymmetric transfer hydrogenation of β,β′-disubstituted nitroalkenes. The catalysis does not involve any direct metal coordination but operates exclusively through weak interactions with functional groups properly arranged in the ligand sphere of the iridium complex.
L-A. Chen, W. Xu, B. Huang, J. Ma, L. Wang, J. Xi, K. Harms, L. Gong, E. Meggers, J. Am. Chem. Soc., 2013, 135, 10598-10601.
A highly enantioselective hydrogenation of enamides is catalyzed by a dual chiral-achiral acid system. By employing a substoichiometric amount of a chiral phosphoric acid and acetic acid, low catalyst loadings of the chiral catalyst were sufficient to provide excellent yield and enantioselectivity of the reduction product.
G. Li, J. C. Antilla, Org. Lett., 2009, 11, 1075-1078.