Reagent

About: Reagent is a research topic. Over the lifetime, 60091 publications have been published within this topic receiving 1234928 citations. The topic is also known as: reagens.

Direct Alkynylation of Thiophenes: Cooperative Activation of TIPS–EBX with Gold and Brønsted Acids

Abstract: United we stand! Cooperative activation of the hypervalent-iodine reagent TIPS-EBX with a gold catalyst and a Bronsted acid allowed the first direct ethynylation of thiophenes at room temperature (see scheme; TFA=trifluoroacetic acid). The obtained ethynylthiophenes are important building blocks for organic dyes and electronic materials.

Facile C–H activation by lutetium–methyl and lutetium–hydride complexes

Abstract: Bis(pentamethylcyclopentadienyl)lutetium complexes Lu(η5-C5Me5)2R (R = Me, H) react at 20–50 °C in hydrocarbon solvents with benzene, pyridine, the ylide CH2PPh3, and tetramethylsilane to give stable, isolatable products of C–H activation, i.e. metallation at a carbon of the reagent with extrusion of R–H.

[104] Means of terminating reactions

Abstract: Publisher Summary Investigations on mitochondrial metabolism include measurements of the instantaneous level of metabolites or the functional state of cofactors. For this purpose, the reactions have to be instantaneously terminated by rapid mixing with a quenching agent. The quenched extract is then available for further analysis of the metabolites. This extraction can be combined with simultaneous continuous recording of spectrophotometric absorption of metabolic components and continuous recording of other functions such as respiration, pH changes, and so on. The requirements for the appropriate quenching method are instantaneous termination of the reaction, which can be followed by an extraction that preserves the metabolites or the cofactors in their functional state. The most widely used quenching reaction is the addition of acid, mostly perchloric acid, which gives an effective inactivation of the enzymes and destruction of the mitochondria. For the extraction of DPNH and TPNH the quenching reagent has to be alkaline; 2 M KOH in ethanol is added to the mitochondrial suspension to give a final concentration of 0.5 M KOH. For the extraction of a lipophilic component, such as ubiquinone, the mitochondrial suspension is rapidly mixed with double its volume of 70% methanol and 30% petroleum ether. For the separate analysis of sediment and medium, the method of sedimentation and separation by a sucrose gradient has been frequently used. Termination of the reaction combined with instantaneous fixation can be accomplished with another type of centrifugal filtration, and is described. Another approach for separating intra- and extramitochondrial metabolites is sieve filtration.