We were very pleased to learn today that the the Nobel Prize in Chemistry 2021 was awarded to Benjamin List (Max-Planck-Institut für Kohlenforschung, Mülheim an der Ruhr, Germany) and David W.C. MacMillan (Princeton University, USA) “for the development of asymmetric organocatalysis”!

The List group is world-famous for developing superacidic organocatalysts, enabling a very wide range of challenging transformations. We are happy that there is also a tiny contribution from our group to prof. List’s research: the acidities (expressed as pK_a values in acetonitrile of 1,2-dichloroethane) of some of their acid catalysts (1,1,3,3-Tetratriflylpropene and some chiral superacidic imides) have been measured in our lab. Recently we were happy to host people from the List group in our lab and they learned how to carry out pK_a measurements in nonaqueous solutions. The collaboration will continue.

Big congratulations to prof. List and to prof. MacMillan!

(Photo: The Nobel Prize committee)

In a recent account Design of Novel Uncharged Organic Superbases: Merging Basicity and Functionality. Acc. Chem. Res. 2021, 54, 3108-3123 four groups doing research at the forefront of superbase chemistry – IOCB (Czech Republic), Rudjer Boskovic Institute (Croatia), Philipps-Universität Marburg (Germany) and our group at University of Tartu – have joined forces in charting the direction for further developments of the whole organosuperbases area. What synthetic chemists need, are “non-ionic, metal-free superbases as chemically stable neutral organic compounds of moderate molecular weight, with intrinsically high thermodynamic basicity, adaptable kinetic basicity, and weak or tunable nucleophilicity at their basicity centres”. Such superbases would be are useful, being able to catalyze a number of reactions that are impossible otherwise.

The account demonstrates that just trying to achieve ever higher basicity is not the main challenge. Very high basicities have been demonstrated, both computationally and experimentally. Instead, the combination of high basicity with moderate molecular weight, ease of synthesis and stability is the key issue.

The account starts with the state of the art of neutral organic superbase research, theirs synthesis and basicity measurements, as well as computations and thereafter presents several examples of emerging organosuperbase families (see the Figure on the left) and discusses their synthesis, basicity and demonstrated, as well as potential applications.

On May 12, 2020 the on-line course (MOOC) Estimation of measurement uncertainty in chemical analysis offered by University of Tartu finished successfully.
Eventually altogether 843 people registered (270 in 2014, 489 in 2015, 757 in 2016, 363 in 2017, 521 in 2018, 590 in 2019) from 95 countries (a number of participants joined after the start of the course). 600 participants actually started the course (i.e. tried at least one graded test at least once) and out of them 464 successfully completed the course (141 in 2014, 169 in 2015, 308 in 2016, 148 in 2017, 358 in 2018, 238 in 2019). The overall completion rate was 55% (52% in 2014, 34% in 2015, 40% in 2016, 41% in 2017, 42% in 2018, 40% in 2019). The completion rate of participants who started the studies was 77% (67% in 2014, 60% in 2015, 67% in 2016, 68% in 2017, 61% in 2018, 62% in 2019). The completion rate this year is the best we have seen and can be considered excellent for a MOOC, especially one that has quite difficult calculation exercises, which need to be done correctly for completing the course.

The participants were very active and asked lots of questions. The questions were often very much to the point and addressed things that are really important to analysts in their everyday work. The course has several forums (general and by topic) and during the course period the overall number of forum posts was close to 600 (!) (overall number of posts, both from participants and from teachers) and the forums are still active and posts are still coming in.

This active participation made teaching of this MOOC a great experience also for us, the teachers. The discussion threads gave a lot of added value to the course and some of them triggered making important modifications to the course materials, even during the course.

We want to thank all participants for helping to make this course a success!

We plan to repeat this course again in Spring 2021.

We recently had the pleasure of collaborating with the group of Daniel Seidel (University of Florida) in the field of enantioselective acidic catalysis. Prof. Seidel and his co-workers have developed Highly Acidic Conjugate‐Base‐Stabilized Enantioselective Carboxylic Acid Catalysts that are able to catalyze oxa‐Pictet–Spengler Reactions with Ketals. Our task in this endeavor was determining the acidity of the catalysts involved and elucidating the effect of the different elements of its substitution scheme on acidity. The main outcome is summarized in the scheme on the left. As can be seen, the most acidifying element is the substituted thiourea moiety, leading to one of the catalysts – the rightmost molecule. The findings strongly suggest that a key to the high acidity is the intramolecular hydrogen bond stabilizing the anion of the acid catalyst. These same substituents are also instrumental in the enantioselective catalytic ability of these catalysts.

This work has been published in Angew. Chem. Int. Edit. 2019.

On Tuesday, November 26, 2019 the web course LC-MS Method Validation was launched by our group for the fourth time as a MOOC (Massive Online Open Course). There are 511 registered participants (the largest number ever in this course) from 77 countries, ranging from Guatemala to Azerbaijan and from Finland to Sudan. Image on the left shows the countries where the participants come from.

This is a practice-oriented on-line course on validation of analytical methods, specifically using LC-MS as technique. The course introduces the main concepts and mathematical apparatus of validation, covers the most important method performance parameters and ways of estimating them. The LC-MS validation course is delivered by a team of 8 teachers form our group, each with their own specific area of competence. This way it is expected to offer the best possible knowledge in all the different subtopics of analytical method validation.

The full set of course materials is accessible from the web page https://sisu.ut.ee/lcms_method_validation/. The course materials include videos, schemes, calculation files and numerous self-tests (among them also full-fledged calculation exercises). In order to pass the course the registered participants have to take all tests and get higher than 50% score from each of them. These tests are available to registered participants via the Moodle e-learning platform. Participants who successfully pass the course will get a certificate from the University of Tartu.

In a recent minireview, published in Eur. J. Org. Chem. an important part of our group’s acid-base chemistry research has been summarized: the pK_a values of bases (pK_aH values) determined over the years in acetonitrile have now been rigorously united into a single scale, whereby all the involved ΔpK_a values have been considered for deriving the absolute pK_aH values of the bases involved. Altogether 279 basic compounds are included in the scale from all major groups of organic bases (amines, pyridines, imidazoles, anilines, amidines, guanidines, phosphazenes, etc) and are linked with altogether 682 ΔpK_a measurements. The full scale can be downloaded by clicking on the picture on the left. The minireview also presents possibilities to predict the pK_a values of bases in other media – namely water, DMSO and THF – on the basis of MeCN pK_aH values. It is expected that this minireview will be a useful tool for future researchers who need pK_a values of bases in nonaqueous solvents for planning their studies or for interpreting research results.