Our research focuses on the investigation of novel catalytic systems and/-or processes for small molecule activation (hydrogen, carbon dioxide, oxygen, and water) related to major chemical transformations including oxidation, reduction, C-H activation and C-C coupling reactions. In the development of new catalysts and catalytic methods also the fundamental issues of sustainability, efficiency and selectivity (ie. "greenness", collectively) are addressed. More specifically, our efforts can be divided into the following topics:
- Frustrated Lewis Pair (FLP) catalysts
- Carbon dioxide activation
- Oxidation catalysis
- Biomass valorization
- Dissolution of noble metals
Since 2008 our research group has centred towards pioneering metal-free activation of hydrogen and metal-free hydrogenation reactions, utilizing a Frustrated Lewis Pair (FLP) approach. FLPs are compounds containing both Lewis acidic and Lewis basic moieties, where the formation of a Lewis adduct is prevented by steric hindrance. These compounds are therefore highly reactive and have been shown to be capable of heterolysis of molecular hydrogen, a property that has led to their use in hydrogenation reactions of polarized multiple bonds.
Representative example: K. Chernichenko, Á. Madarász, I. Pápai, M. Nieger, M. Leskelä, T. Repo. "A frustrated-Lewis-pair approach to catalytic reduction of alkynes to cis-alkenes." Nat. Chem. 5 (2013) pp. 718-723.
While looking for new and renewable raw material resources for the chemical industry, which is nowadays mainly based on fossil fuels, coal, or crude oil, carbon dioxide is an attractive alternative. It is abundant, inexpensive, and nonflammable gas and can be, therefore, considered as an ideal candidate as C1-carbon source for synthesis. During the last 10 years, we have carried out basic research related to CO2 activation. Initially, our research focused on the development of novel transition metal catalysts for the cycloaddition of carbon dioxide to epoxides, a reaction which yields cyclic carbonates that are employed as polar solvents, electrolytes, and reagents in polymer chemistry:
A recent example: F. Al-Qaisi, N. Genjang, M. Nieger, T. Repo. "Synthesis, structure and catalytic activity of bis(phenoxyiminato)iron(III) complexes in coupling reaction of CO2 and epoxides." Inorg. Chim. Acta 442 (2016) pp. 81-85.
More recently, our focus has shifted towards the synthesis of cyclic carbamates (aka. cyclic urethanes) from carbon dioxide and amines. This structure, and especially the 5-membered ring oxazolidinone, is found in many pharmaceuticals - most notably the antibiotic Linezolid®. In a 2016 manuscript, we showed how 5-7-member ring systems containing the urethane functionality can be synthesized from carbon dioxide, anilines, and dihaloalkanes in a single step, using a simple organocatalyst and mild reaction conditions:
From: T. Niemi, J. E. Perea-Buceta, I. Fernández, O.-M. Hiltunen, V. Salo, S. Rautiainen, M. T. Räisänen, T. Repo. "A One-Pot Synthesis of N-Aryl-2-Oxazolidinones and Cyclic Urethanes by the Lewis Base Catalyzed Fixation of Carbon Dioxide into Anilines and Bromoalkanes." Chem. Eur. J. 22 (2016) pp. 10355-10359.
Environmentally benign selective oxidation reactions are urgently needed in the pharmaceutical and chemical industries. Hydrogen peroxide (H2O2) and molecular oxygen (O2) represent ideal alternatives to commonly used stoichiometric oxidants such as Cr(VI) and Mn(VII). However, the use of H2O2 or O2 in the oxidation of organic molecules generally requires the use of a catalyst for obtaining high reactivity and selectivity. Our research has been focused on the development and mechanistic characterization of organometallic and organic catalysts for these transformations. Over the past years, this research has been among the most active and fastest advancing fields of catalytic chemistry, enabling versatile new approaches for selective transformations, including selective dehydrogenation of alcohols and amines, oxidative carbonylation, and C-H functionalization. Our research group is currently investigating new catalysts for selective oxidation of alcohols with environmentally benign Fe, Mn, Cu, and metal-free systems.
Further information: K. Lagerblom, P. Wrigstedt, J. Keskiväli, A. Parviainen, T. Repo. "Iron-Catalysed Selective Aerobic Oxidation of Alcohols to Carbonyl and Carboxylic Compounds." ChemPlusChem 81 (2016) pp. 1160-1165.
The increasing global demand for sustainable chemicals and fuels has drawn a tremendous amount of interest towards renewable resources. Lignocellulosic biomass has been recognized as one of the most promising options to replace fossil feedstocks due to the price, abundancy and versatility as a substrate. As part of the worldwide pursuit to harness the full potential of lignocellulosic biomass, we are involved in the development of fine-chemical synthesis and related biofuel and biopolymer processes. We have studied the catalytical defunctionalization of biomass-based substrates into value-added chemicals, such as platform molecule 5-(hydroxymethyl)-furfural (HMF), and branched alkanes to serve as potential biofuels. Currently, we are investigating the synthesis of olefins, involving transition metal-catalyzed cleavage of ethers and removal of alcohol functionalities from naturally occurring molecules as substrates.
For more information, see our recent manuscript: J. Keskiväli, P. Wrigstedt, K. Lagerblom, T. Repo. "One-step Pd/C and Eu(OTf)3 catalyzed hydrodeoxygenation of branched C11 and C12 biomass-based furans to the corresponding alkanes." Appl. Catal. A. Gen. 534 (2017) pp. 40-45.
An approach that has remained mostly unexploited for dissolution of noble metals is based on the use of organic compounds/solvents. The emphasis is in the characterization of group 11 metal complexes, namely Au(I/III)-, Ag(I)- and Cu(I/II) complexes, formed during the dissolution reaction which further are of great importance when investigating the mechanism. Altogether, oxidative dissolution reactions are complex and consist of many different side reactions occurring in solution. In previous studies made in our group, 4-pyridinethiol was discovered to have the ability to dissolve gold in alcohol solutions as Au(I)thiolato complex. The scope of ligands has since been extended with various thiol-thione-based S-donor ligands and new efficient systems have been found using computational methods. In a larger context, the results from this project can influence environmental and health implications of mining and sustainable processing of noble metals from mineral and secondary resources. The solution is in the solution!