Chloride mediated effect

A titanium(iv) chloride mediated Baylis-Hillman-type or aldol reaction between a-ketoesters and cyclohex-2-enones has been studied (Equation (13)).77 The steric effect of the R2 substituent is crucial for the reaction pathway since the aldol reaction only proceeds with the unsubstituted cyclohexenone (aldol adduct 71 with R2 = H to a small extent the Baylis-Hillman reaction occurs), whereas with the substituted substrate (R2 = Me) gives exclusively the Baylis-Hillman adduct 72. 

Bergman described indole C-3 acylation with acid chlorides via 1-indolylzinc chloride in the absence of palladium [108]. Davidsen and co-workers synthesized 86, which is a potent antagonist of platelet activating factor-mediated effects, using this Bergman acylation sequence... 

Chloride is mostly described in relation to hydrogen, sodium, potassium, and calcium, except when deviations are well described specifically for Cl in biological systems as a result of deficiency or excess availability. In addition, dysfunctions of CD transport or CD channels are of clinical relevance and have indeed been the subject of intensive research. One principle of CD-mediated effects is a change in osmotic condition, cell volume, and excitability and in acid-base balance in biological systems. In this way, CD is essentially linked to water distribution and electrolyte turnover. 

As for the oxidative cyclization that uses iron(III) chloride, to effectively suppress the polymerization, the DDQ/acid-mediated variant of the SchoU reaction requires the blocking of the a positions of thiophene rings. 

In addition to the photo-generation, Carell and coworkers showed that the hydrazonyl chloride (13) could also serve as a precursor to the reactive nitrile imine (17a) in neutral aqueous buffer [23]. Intrigued by these results, Liu and coworkers conducted a mechanistic study of the hydrazonyl chloride-mediated cycloaddition by examining the effects of pH and chloride concentration on the rates of nitrile imine formation and subsequent cycloaddition reactions [24]. They concluded that... 

Among the seven lanthanides screened, praseodymium(iii), ytterbium(iii) and neodymium(//7) triflates were shown to be most effective. Magnesium chloride and lithium chloride showed no substantial influence on these reactions, thereby ruling out the salt effect for explaining the rate and yield enhancements of lanthanides. The details of the catalytic mechanism of this intriguing lanthanide-mediated effect are under investigation. 

Cross-coupling. Heteroarenes, such as 1,3,4-oxadiazole and oxazole, efficiently undergo a copper(II) chloride-mediated oxidative coupling with terminal alkynes (eq 34). Electron-rich alkynes effectively coupled with 2-phenyl-1,3,4-oxadiazole, although electron-deficient substrates led to a decreased yield. The 1,3,4-oxadiazoles with various substituents at the 2-position were also suitable substrates, but the slow addition of terminal alkynes was essential to avoid undesired diyne formation. The desired 2-alkynyl-5-aryloxazoles were obtained in DMSO at 150 °C. 

Ghauri MS, Thomas JDR (1994) Evaluation of an anunonium ionophore for use in poly(vinyl chloride) membrane ion-selective electrodes solvent mediator effects. Analyst 119 2323-... 

Preferential flow through root-mediated soil pores has been demonstrated for chloride, nitrate, and other ions that are not sorbed onto soil organic matter and clays. However, pesticide sorption onto soil affects both mobiUty of the pesticide as well as its residual life in the soil. Pesticide sorption onto root organic matter or organic linings of worm burrows may also slow transport of pesticides relative to water (72), thus countering the effects of increased permeabihty caused by roots. 

Indeed, cumyl carbocations are known to be effective initiators of IB polymerization, while the p-substituted benzyl cation is expected to react effectively with IB (p-methylstyrene and IB form a nearly ideal copolymerization system ). Severe disparity between the reactivities of the vinyl and cumyl ether groups of the inimer would result in either linear polymers or branched polymers with much lower MW than predicted for an in/mcr-mediated living polymerization. Styrene was subsequently blocked from the tert-chloride chain ends of high-MW DIB, activated by excess TiCU (Scheme 7.2). 

Later, Torii et al. found that the tin-aluminum-mediated allylation can be carried out with the less expensive allyl chloride, instead of allyl bromide, when a mixture of alcohol-water-acetic acid was used as the solvent.77 When combined with stoichiometric amounts of aluminum powder, both stoichiometric and catalytic amounts of tin are effective. As reported by Wu et al., higher temperatures can be used instead of aluminum powder.78 Under such a reaction condition, allyl quinones were obtained from 1,4-quinones, followed by oxidation with ferric chloride. Allylation reactions in water/organic solvent mixtures were also carried out electrochemically, with the advantage that the allyltin reagent could be recycled.79... 

Whitesides et al. examined the effect of substituents on the allyllic moiety of the indium-mediated reactions in water and found that the use of indium at room temperature gave results comparable to those of tin-mediated reactions carried out at reflux.110 Replacement of the aqueous phase with 0.1 N HC1 further increased the rate of the reaction. The transformation can also be carried out with preformed allylindium chloride. 

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