New organocatalysis paper in OBC

In new research, carried out in University of Bern, we have shown that triazolium iodides are excellent catalysts for the oxidative coupling of benzylamines, due to a synergistic cation/anion effect, with iodide acting as I/I2 redox manifold and the triazolium cation facilitating the iodine reduction and concomitant substrate oxidation. Oxygen was is the terminal oxidant for this process.

The article is available at: https://doi.org/10.1039/D0OB01472A (Open access in Organic and Biomolecular Chemistry, Themed Collection: Catalysis and Biocatalysis in OBC)

The research emerged from the dual interest in the Albrecht group in catalysis and the use of triazolium salts – typically as precursors to organometallic complexes. Joe followed up on some unexpected catalytic activity of triazolium iodides with a series of experiments and control experiments to determine the origins of the reactivity, the role of atmospheric oxygen as terminal oxidant, the importance of the iodide/iodine redox couple and the accelerating effect of the triazolium ion. We hope this work will inspire others to look at the role of heterocylcic compounds in other processes catalysed by iodine.

New paper in ChemCatChem

Joe was part of a collaborative project between University of Bern (Switzerland) and Universitat Jaume I (Spain), which was recently published in ChemCatChem. This work describes the use of mesoionic iridium(III)-NHC complexes as catalysts for efficient dehydrogenation of carbohydrates in water. Without the need for additives, these complexes compare were to previous work published by Dr Jose Mata’s group, using imdazolylidene iridium(III) complexes, along with sulfuric acid.

DOI: 10.1002/cctc.202000544R1

Introducing abnormal triazolylidene NHC complexes from the Albrecht lab, allowed for this further enhancement of activity for this interesting reaction, which releases hydrogen from carbohydrate substrates, giving only the carbohydrate acid (e.g. gluconic acid) as a by-product, which has potential utility as a initial platform chemical for further synthesis, derived from biomass feedstocks.

New publication in Dalton Transactions

I’m delighted to finally publish this work, the first of my research carried out during my Marie Curie Fellowship in University of Bern to come out. A lot of hard work by Erasmus student Pauline went into gathering data behind this manuscript where we asked the question – what impact would incorporating carbohydrates into the structure of a Ruthenium(II)-triazolylidene complex have on its ability to convert a ketone to an alcohol via transfer hydrogenation catalysis.

There were challenges in isolating the desired compound, so it had to be generated in situ, but we were able to assess the activity, and the results were interesting, and can be found in detail here in Dalton Transactions.

To summarise the conclusions: The carbohydrate functionality does impact catalytic activity (transfer hydrogenation of ketones). In complexes with the glucose directly triazolylidene-bound,  turnover rates were substantially higher when compared to more remote carbohydrate functionalisation (i.e. with an ethylene spacer). Both new complexes, however, have reduced activity compared to  unfunctionalised carbene complexes. Insight was also gained into the nature of the catalytic cycle through a substrate scope analysis.