of the hydrogenation product formed, which does not happen with shorter chain
internal alkenes under the same conditions, led the authors to conclude that the
isomerization step is much slower for this substrate. [Ir(cod)Cl] 2 gave no borylation
product under the same conditions. When the reaction temperature was increased to
50
C, a low yield of 25% was achieved, with a large amount of the starting material
still present after 24 h.
8 Conclusion
In this chapter we have summarized research in the field of iridium-catalyzed
biomass conversion. This is a developing field, most of the work discussed here
was published in the last 8 years. With the recent progress in the conversion of
cellulosic biomass and the availability of several platform chemicals, there is now
more and more scope for homogeneous catalysis in this area, due to its generally
higher selectivity at milder conditions. We therefore expect to see more publications
in this field in the future. One massive advantage of iridium over other metals,
especially with regard to biomass, is its excellent stability towards water, air, and
acidic conditions. We have seen that a range of useful fine chemicals and precursors,
monomers, and even polymers can be synthesized from biomass using iridium
catalysis. Mechanistically, many of the reactions discussed are hydrogenation/dehydrogenation reactions. This is an important reaction pathway for biomass, which is
highly functionalized and oxygen-rich compared to the well-known oil-based building blocks. Other mechanisms such as decarbonylation/hydroformylation and others
have also been applied to bio-based compounds. The valorization of lignin still lags
behind the saccharide-based biomass but also here iridium catalysts have shown
promising potential in the initial defunctionalization and the selective generation of a
few monomers from the complex mixture. We expect to see more research in this
direction in the coming years.
Finally, the dehydrogenation of biomass to generate hydrogen, a highly useful
product with the potential to be a main energy carrier in the future is also being
investigated. With the development of more efficient catalysts, the generation of
renewable hydrogen from biomass should soon become cost-effective.
References
1. Werpy T, Petersen G (2004) Top value added chemicals from biomass volume I – results of
screening for potential candidates from sugars and synthesis gas. https://doi.org/10.2172/
15008859
2. Bozell JJ, Petersen GR (2010) Technology development for the production of biobased
products from biorefinery carbohydrates-the US Department of Energy's “top 10” revisited.
Green Chem 12:539–554
Homogenous Iridium Catalysts for Biomass Conversion
389
internal alkenes under the same conditions, led the authors to conclude that the
isomerization step is much slower for this substrate. [Ir(cod)Cl] 2 gave no borylation
product under the same conditions. When the reaction temperature was increased to
50
C, a low yield of 25% was achieved, with a large amount of the starting material
still present after 24 h.
8 Conclusion
In this chapter we have summarized research in the field of iridium-catalyzed
biomass conversion. This is a developing field, most of the work discussed here
was published in the last 8 years. With the recent progress in the conversion of
cellulosic biomass and the availability of several platform chemicals, there is now
more and more scope for homogeneous catalysis in this area, due to its generally
higher selectivity at milder conditions. We therefore expect to see more publications
in this field in the future. One massive advantage of iridium over other metals,
especially with regard to biomass, is its excellent stability towards water, air, and
acidic conditions. We have seen that a range of useful fine chemicals and precursors,
monomers, and even polymers can be synthesized from biomass using iridium
catalysis. Mechanistically, many of the reactions discussed are hydrogenation/dehydrogenation reactions. This is an important reaction pathway for biomass, which is
highly functionalized and oxygen-rich compared to the well-known oil-based building blocks. Other mechanisms such as decarbonylation/hydroformylation and others
have also been applied to bio-based compounds. The valorization of lignin still lags
behind the saccharide-based biomass but also here iridium catalysts have shown
promising potential in the initial defunctionalization and the selective generation of a
few monomers from the complex mixture. We expect to see more research in this
direction in the coming years.
Finally, the dehydrogenation of biomass to generate hydrogen, a highly useful
product with the potential to be a main energy carrier in the future is also being
investigated. With the development of more efficient catalysts, the generation of
renewable hydrogen from biomass should soon become cost-effective.
References
1. Werpy T, Petersen G (2004) Top value added chemicals from biomass volume I – results of
screening for potential candidates from sugars and synthesis gas. https://doi.org/10.2172/
15008859
2. Bozell JJ, Petersen GR (2010) Technology development for the production of biobased
products from biorefinery carbohydrates-the US Department of Energy's “top 10” revisited.
Green Chem 12:539–554
Homogenous Iridium Catalysts for Biomass Conversion
389