Hydrogen
Name Reactions
Recent Literature
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.
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 mild, complete hydrogenation of aromatic rings catalyzed by heterogeneous 10%
Rh/C proceeds at 80 °C in water under 5 atm of H2 pressure and is
applicable to the hydrogenation of various carbon and heteroaromatic compounds
such as alkylbenzenes, biphenyls, pyridines and furans.
Maegawa, A. Akashi, H. Sajiki, Synlett,
2006, 1440-1442.
An iron complex containing electronically coupled acidic and hydridic hydrogens
catalyzes the hydrogenation of ketones under mild conditions and shows high
chemoselectivity for aldehydes, ketones, and imines. Isolated carbon double and
triple bonds, aryl halides, nitrates, epoxides, and ester functions are
unaffected by the hydrogenation conditions.
C. P. Casey, H. Guan, J. Am. Chem. Soc., 2007,
129, 5816-5817.
Ruthenium carbene complexes catalyze ring closing metathesis (RCM) and a
subsequent hydrogenation after activation with sodium hydride. Hydrogenation of
cyclopentenols proceeds smoothly at ambient temperature and under 1 atm of
hydrogen in toluene.
B. Schmidt, M. Pohler, Org. Biomol. Chem.,
2003,
1, 2512-2517.
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.
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.
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.
Ruthenium complexes of rigid diphosphane ligands with large dihedral angles
are highly efficient catalysts for the asymmetric hydrogenation of
α,β-unsaturated carboxylic acids.
X. Cheng, Q. Zhang, J.-H. Xie, L.-X. Wang, Q.-L. Zhou, Angew. Chem. Int. Ed.,
2005,
44, 1118-1121.
A rhodium-catalyzed methylenation-hydrogenation cascade process allows the
homologation of carbonyl compounds to alkanes in high yields.
H. Lebel, C. Ladjel, J. Org. Chem., 2005, 70, 10159-10161.
A heterogeneous platinum catalyst efficiently mediates the reductive
etherification of ketones at ambient hydrogen pressure. In this transformation,
water is released as the only by-product, and this is trapped with molecular
sieves.
L. J. Gooßen, C. Linder, Synlett, 2006,
3489-3491.
A magnetically separable palladium catalyst is highly active and selective
for epoxide hydrogenolysis at room temperature under 1 atm H2 and can
be recycled without loss of activity. The catalyst was synthesized simply
through a sol-gel process incorporating palladium nanoparticles and
superparamagnetic iron oxide nanoparticles in aluminum oxyhydroxide matrix.
M. S. Kwon, I. S. Park, J. S. Jang, J. S. Lee, J. Park, Org. Lett., 2007,
9, 3417-3419.
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.
Various enantiomerically pure α-hydroxy esters were synthesized by a Ru-Cn-Tunephos-catalyzed
asymmetric hydrogenation of α-keto esters. High enantiomeric excess has been
achieved for both α-aryl and α-alkyl substituted α-keto esters.
C.-J. Wang, X. Sun, X. Zhang, Synlett,
2006, 1169-1172.
An iridium-catalyzed, hydrogen-mediated reductive C-C bond formation of
alkynes in the presence of α-ketoesters affords β,γ-unsaturated α-hydroxyesters in
excellent yield, with complete control of olefin geometry and, in most cases,
with excellent regiocontrol.
M.-Y. Ngai, A. Barchuk, M. J. Krische, J. Am. Chem. Soc., 2007,
129, 280-281.
A novel enantioselective synthesis of α-amino acids has been developed,
which is broad in scope, simple in application, and advantageous for many α-amino acids
of interest in chemistry, biology, medicine.
E. J. Corey, J. O. Link, J. Am. Chem. Soc., 1992,
114, 1906-1908.
Exposure of various N-arylsulfonyl aldimines to 2-butyne and hydrogen at
ambient pressure in the presence of a cationic iridium(I) catalyst modified by
BIPHEP provides reductive coupling products, allylic amines, in good yields as
single geometrical isomers. Nonsymmetric alkynes couple under standard
conditions with high levels of regioselection.
A. Barchuk, M.-Y. Ngai, M. J. Krische, J. Am. Chem. Soc., 2007,
129, 8432-8433.
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.
Catalytic hydrogenation of 1,3-enynes in the presence of ethyl glyoxalate at
ambient pressure and temperature using a rhodium catalyst modified by (R)-(3,5-tBu-4-MeOPh)-MeO-BIPHEP
results in highly regio- and enantioselective reductive coupling to furnish the
corresponding α-hydroxy esters.
Y.-T. Hong, C.-W. Cho, E. Skucas, M. J. Krische, Org. Lett., 2007,
9, 3745-3748.
Highly enantioselective direct catalytic reductive couplings of 1,3-enynes to
activated ketones such as ethyl pyruvate have been achieved by using chirally
modified cationic rhodium catalysts in the presence of hydrogen to afford
dienylated α-hydroxy esters with exceptional levels of regio-
and enantiocontrol.
J.-R. Kong, M.-Y. Ngai, M. J. Krische, J. Am. Chem. Soc., 2006, 128, 718-719.
