Alcohols Used to Replace Hydrogen in Reduction Reactions

  • Author: ChemistryViews.org
  • Published: 24 October 2019
  • Copyright: Wiley-VCH Verlag GmbH & Co. KGaA
  • Source / Publisher: Chemical Communications/Royal Society of Chemistry
  • Associated Societies: Royal Society of Chemistry (RSC), UK
thumbnail image: Alcohols Used to Replace Hydrogen in Reduction Reactions

Using hydrogen gas directly in reduction reactions can be problematic due to the need for high-pressure equipment. Catalytic transfer hydrogenations with an H2 equivalent can avoid this issue. Alcohols, for example, can be used to replace H2 in this type of reaction. However, this approach has so far not been used for copper-catalyzed homogeneous transfer hydrogenations. Usually, these processes use hydrosilanes as reducing agents, which generates stoichiometric amounts of silicon-based waste products.


Johannes F. Teichert and colleagues, Technical University of Berlin, Germany, have developed a protocol for the copper-catalyzed transfer semihydrogenation of alkynes (pictured) that uses simple, low-cost alcohols such as isopropanol as hydrogen sources. The team used a complex of the type  [NHC–Cu–Cl] as the catalyst (NHC = N-heterocyclic carbene), NaOtBu as a base, and isopropanol as the solvent and H2 equivalent, simultaneously.


The reaction was performed at 140 °C and converted different disubstituted alkynes to the desired alkenes in moderate to excellent yields and with good Z/E-selectivity. The team found no overreduction to the corresponding alkanes. This stereo- and chemoselectivity is attributed to the NHC ligand: When only CuCl is used as the catalyst, selectivities drop significantly and alkanes are formed.


 

Article Views: 930

Sign in Area

Please sign in below

Additional Sign In options

Please note that to comment on an article you must be registered and logged in.
Registration is for free, you may already be registered to receive, e.g., the newsletter. When you register on this website, please ensure you view our terms and conditions. All comments are subject to moderation.

Article Comments - To add a comment please sign in

Bookmark and Share

If you would like to reuse any content, in print or online, from ChemistryViews.org, please contact us first for permission. more


CONNECT:

ChemistryViews.org on Facebook

ChemistryViews.org on Twitter ChemistryViews.org on YouTube ChemistryViews.org on LinkedIn Sign up for our free newsletter


A product of ChemPubSoc Europe (16 European Chemical Societies)and Wiley-VCH