Enhancing Carbon Acid pKa Prediction by Augmentation of Sparse Experimental Datasets with Accurate AIBL (QM) Derived Values

The prediction of the aqueous pKa of carbon acids by Quantitative Structure Property Relationship or cheminformatics-based methods is a rather arduous problem. Primarily, there are insufficient high-quality experimental data points measured in homogeneous conditions to allow for a good global model to be generated. In our computationally efficient pKa prediction method, we generate an atom-type feature vector, called a distance spectrum, from the assigned ionisation atom, and learn coefficients for those atom-types that show the impact each atom-type has on the pKa of the ionisable centre. In the current work, we augment our dataset with pKa values from a series of high performing local models derived from the Ab Initio Bond Lengths method (AIBL). We find that, in distilling the knowledge available from multiple models into one general model, the prediction error for an external test set is reduced compared to that using literature experimental data alone.

Orthoamide und Iminiumsalze, C. Vinyloge Guanidiniumsalz-basierte ionische Flüssigkeiten sowie phenyloge Guanidiniumsalze und Orthoamide

Cyclopropylacetylene and N,N,N′,N′,N′′,N′′-hexamethylguanidinium chloride (1a) react to give the orthoamide derivative 8c, in the presence of sodium hydride. 8c is transformed by elemental iodine to the vinylogous guanidinium salt 6f. Anion metathesis with the salts 5a, 5e, 6g delivers vinylogous guanidinium salts 5e–5i, 12a with counter ions derived from carbon acids (tricyanomethane, 1,1,3,3-tetracyano-propene). Phenylogous amidinium salts 15 guanidinium salts 19, 21 and the phenylogous orthoamide derivatives of formic acid 18 and carbonic acid 33 have been prepared.

A catalyst-free bis(triflyl)ethylation/benzannulation reaction: rapid access to carbazole-based superacidic carbon acids from alkynols

A metal- and irradiation-free preparation of Tf2CHCH2-decorated carbazoles from 1-(indol-2-yl)but-3-yn-1-ols under mild conditions with a 2-fluoropyridinium salt as the Tf2CCH2 source has been attained in a straightforward and selective manner.

Persistent Radical Pairs Between N-Substituted Naphthalimide and Carbanion Exhibit pKa-Dependent UV-vis Absorption

A new strategy is constructed for estimating and screening pK_a values among different carbon acids under ambient conditions via the UV-vis absorption spectrum of persistent radical pair originating from an <i>N</i>-substituted naphthalimide (NNI) derivative in the presence of various carbanions in organic solutions

Persistent Radical Pairs Between N-Substituted Naphthalimide and Carbanion Exhibit pKa-Dependent UV-vis Absorption

A new strategy is constructed for estimating and screening pK_a values among different carbon acids under ambient conditions via the UV-vis absorption spectrum of persistent radical pair originating from an <i>N</i>-substituted naphthalimide (NNI) derivative in the presence of various carbanions in organic solutions

Persistent Radical Pairs Between N-Substituted Naphthalimide and Carbanion Exhibit pKa-Dependent UV-vis Absorption

A new strategy is constructed for estimating and screening pK_a values among different carbon acids under ambient conditions via the UV-vis absorption spectrum of persistent radical pair originating from an <i>N</i>-substituted naphthalimide (NNI) derivative in the presence of various carbanions in organic solutions