2014-75-7Relevant articles and documents
Engineering Catalysts for Selective Ester Hydrogenation
Dub, Pavel A.,Batrice, Rami J.,Gordon, John C.,Scott, Brian L.,Minko, Yury,Schmidt, Jurgen G.,Williams, Robert F.
, p. 415 - 442 (2020/03/04)
The development of efficient catalysts and processes for synthesizing functionalized (olefinic and/or chiral) primary alcohols and fluoral hemiacetals is currently needed. These are valuable building blocks for pharmaceuticals, agrochemicals, perfumes, and so forth. From an economic standpoint, bench-stable Takasago Int. Corp.'s Ru-PNP, more commonly known as Ru-MACHO, and Gusev's Ru-SNS complexes are arguably the most appealing molecular catalysts to access primary alcohols from esters and H2 (Waser, M. et al. Org. Proc. Res. Dev. 2018, 22, 862). This work introduces economically competitive Ru-SNP(O)z complexes (z = 0, 1), which combine key structural elements of both of these catalysts. In particular, the incorporation of SNP heteroatoms into the ligand skeleton was found to be crucial for the design of a more product-selective catalyst in the synthesis of fluoral hemiacetals under kinetically controlled conditions. Based on experimental observations and computational analysis, this paper further extends the current state-of-the-art understanding of the accelerative role of KO-t-C4H9 in ester hydrogenation. It attempts to explain why a maximum turnover is seen to occur starting at 25 mol % base, in contrast to only 10 mol % with ketones as substrates.
Synthesis and biological evaluation of heteroalicyclic cyanoguanidines at histamine receptors
Soliman, Beatrice,Wang, Ning,Zagotto, Giuseppe,Pockes, Steffen
, (2019/08/12)
Recent studies on histamine receptor (HR) subtypes identified imidazolyl butyl cyanoguanidines, like UR-PI376, as highly potent agonists at the human histamine H4 receptor (hH4R). While imidazole-containing compounds display drawbacks in pharmacokinetics, we studied the possibility of?replacing?the heteroaromatic cycle by nonaromatic six-membered heterocycles (piperidine, morpholine, thiomorpholine, and?N-methylpiperazine) as potential bioisosteres. Beyond that, this approach should give more information about the indispensability of the?aromatic ring as a basic head group. Besides these changes, a variation of the spacer length (C3–C5) connecting the heterocycle and the cyanoguanidine moiety has been made to possibly trigger the selectivity towards the respective HRs. Investigations in radioligand-binding assays exhibited only very weak activity at the hH1R and hH3R, while nearly all compounds were inactive at the hH2R and hH4R. In the case of piperidine-containing compounds, moderate affinities at the hH3R over the single-digit micromolar range were detected.
Insights into the Pummerer synthesis of oxazolines
Becerra-Cely, Laura,Rueda-Espinosa, Juan,Ojeda-Porras, Andrea,Gamba-Sánchez, Diego
, p. 8474 - 8485 (2016/09/28)
A rapid and simple method to access unnatural 2-substituted 5-thio oxazolines has been developed. This methodology is based on a Pummerer reaction followed by an intramolecular nucleophilic substitution, which changes the paradigm for the normal use of a base in Pummerer chemistry. We also provide a useful two-step method for the synthesis of the starting material and a mechanistic proposal based on experimental observations, which contests the previously proposed reaction pathway. The reaction proved to be general, and different substituents, such as alkyl, aryl, alkenyl and functionalized groups, can be used without a significant decrease in efficiency.
