No abstract

Solubility prediction remains a critical challenge in drug development, synthetic route and chemical process design, extraction and crystallisation. Here we report a successful approach to solubility prediction in organic solvents and water using a combination of machine learning (ANN, SVM, RF, ExtraTrees, Bagging and GP) and computational chemistry. Rational interpretation of dissolution process into a numerical problem led to a small set of selected descriptors and subsequent predictions which are independent of the applied machine learning method. These models gave significantly more accurate predictions compared to benchmarked open-access and commercial tools, achieving accuracy close to the expected level of noise in training data (LogS ± 0.7). Finally, they reproduced physicochemical relationship between solubility and molecular properties in different solvents, which led to rational approaches to improve the accuracy of each models.

This tutorial bridges an important knowledge gap by providing an easily accessible introduction that enables synthetic chemists to explore synthetic electrochemistry.

A mechanistic investigation into the guanidine catalyzed reductive amination of CO 2 , using a combination of 1 H, 29 Si NMR, FT-IR, MS and GC profiling, is reported. Inexpensive and readily available N N N N-tetramethylguanidine (TMG) was found to be an equally effective catalyst compared to more elaborate cyclic guanidines. Different catalytic pathways to formamide 2, aminal 4 and N-methylamine 3, were identified. A pathway to formamide product 2 dominates at 23 °C. Increasing the reaction temperature to 60 °C enables a competitive, higher energy pathway to 4 and 3, which requires direct reduction of CO 2 with PhSiH 3 to formoxysilane E. Reduction of aminal 4, in the presence of CO 2 and the catalyst, led to formation of a 1 : 1 ratio of 2 and 3. The catalyst itself can be formylated under the reaction conditions, resulting in its deactivation. Thus, alkylated TMGs were found to be more stable and more active catalysts than TMG, leading to a successful organocatalyzed reductive functionalization of CO 2 with silane at 0.1 mol% catalyst loading (TON = 805 and TOF = 33.5 h-1).

The palladium-catalyzed three-component coupling of aryl iodides, sulfur dioxide, and hydrazines to deliver aryl N-aminosulfonamides is described. The colorless crystalline solid DABCO·(SO(2))(2) was used as a convenient source of sulfur dioxide. The reaction tolerates significant variation of both the aryl iodide and hydrazine coupling partners.

Generation of catalytically active Pd(0) species from Pd(OAc) 2 has been examined, in the context of Suzuki-Miyaura reactions involving substitution of aryl bromides under aerobic and ambient conditions. Using a combination of spectroscopic, microscopic and kinetic measurements, the role of each reaction component is delineated in the speciation of the palladium species. Among the key findings are the effects of O 2 , H 2 O and inorganic base, and implications for catalytic activity.

A universal multistage cascade CSTR has been developed that is suitable for a wide range of continuous-flow processes. Coined by our group the “Freactor” (free-to-access reactor), the new reactor integrates the efficiency of pipe-flow processing with the advanced mixing of a CSTR, delivering a general “plug-and-play” reactor platform which is well-suited to multiphasic continuous-flow chemistry. Importantly, the reactor geometry is easily customized to accommodate reactions requiring long residence times (≥3 h tested).

Highlights: A custom-made plug-flow reactor (PFR) was constructed for examining Pd catalysis  Leaching/reaction profiles of two Pd catalysts for the Suzuki-Miyaura reaction were established by filtration studies.  The PFR was used to examine catalyst activation and deactivation processes  Ethanol was found to affect the catalysts differently  Leaching and speciation of Pd along the catalyst bed has been observed for the very first time. Catal Today (Highlights