Categories: C-H Bond Formation >
Reduction of Alkynes
An unprecedented reduction of alkynes with formic acid can selectively produce cis-, trans-alkenes and alkanes by slightly tuning the reaction conditions via the generation of an alkenylpalladium intermediate and subsequent transformation of this complex in a variety of reactions catalyzed by a combination of Brønsted acid and Pd(0) complex.
R. Shen, T. Chen, Y. Zhao, R. Qiu, Y. Zhou, S. Yin, X. Wang, M. Goto, L.-B. Han, J. Am. Chem. Soc., 2011, 133, 17037-17044.
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 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.
A NCP-type pincer iridium complex enables an efficient, mild, chemoselective transfer hydrogenation of unactivated C-C multiple bonds with ethanol, forming ethyl acetate as the sole byproduct. A wide variety of alkenes, including multisubstituted alkyl alkenes, aryl alkenes, and heteroatom-substituted alkenes, as well as heteroarenes and internal alkynes, are suitable substrates.
Y. Wang, Z. Huang, X. Leng, H. Zhu, G. Liu, Z. Huang, J. Am. Chem. Soc., 2018, 140, 4417-4429.
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.
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.
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.
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.