Electrophilic compounds

An electrophile or electrophilic compound is a reagent attracted to electrons that participates in a chemical reaction by accepting an electron pair in order to bond to a nucleophile. Because electrophiles accept electrons, they are Lewis acids. Most electrophiles are positively charged, have an atom which carries a partial positive charge, or have an atom which does not have an octet of electrons. The electrophiles attack the most electron-populated part of a nucleophile. 

The best carbonyl components for these reactions are highly electrophilic compounds such as glyocylate, pyruvate, and oxomalonate esters, as well as chlorinated and fluorinated aldehydes. Most synthetic applications of the carbonyl-ene reaction utilize Lewis acids. Although such reactions may be stepwise in character, the stereochemical outcome is often consistent with a cyclic TS. It was found, for example, that steric effects of trimethylsilyl groups provide a strong stereochemical influence.28... 

Protection against cell damage due to oxidative stress is provided, amongst others, by glutathione (GSH), a cellular tripeptide with a thiol function in a cysteine residue. GSH is deprotonated to GS, which is a scavenger for electrophilic compounds and is reduced to GS SG in defense of reactive oxygen species [28]. 

An electron capture detector detects electrophilic compounds. 

Electron capture detectors are extremely sensitive (1 X 10 12 mol) but are specific for electrophilic compounds. However, they can be used in parallel with flame ionization detectors to identify specific peaks in a chromatogram. 

Disproportionation, a common process in inorganic halogen chemistry, does not proceed. For example, lOH(HIO) is an unstable, strongly electrophilic compound and, when no substrate is present. 

P7 Over the past decade, electron monochromator-mass spectrometry (EM-MS) has been shown to be a selective and sensitive technique for the analysis of a wide variety of electrophilic compounds in complex matrixes. Here, for the hrst time, three different dinitroaniline pesticides, flumetralin, pendimethalin, and trifluralin, have been shown to be present in both mainstream and sidestream tobacco smoke using an EM-MS system. (From Dane et ah, 2006)... 

The polydispersity of polymers prepared in this way is usually very low for example, a value MJM of 1.05 was found for a sample of poly(a-methylsty-rene). Living polymers can also be used for the preparation of block copolymers after the consumption of the first monomer, a second anionically polymerizable monomer is added which then grows onto both ends of the initially formed block. By termination of the living polymer with electrophilic compounds the polymer chains can be provided with specific end groups for example, living polystyrene reacts with carbon dioxide to give polystyrene with carboxylic end groups. 

Table 3. Reactions of Uthiomethyl-diphenyl-arsaneoxide with electrophilic compounds...

As the bioactivation of halons may afford electrophilic compounds that may react with the thiol moiety of cysteines included in proteins, the in vivo toxicity of these adducts has been studied. ... 

Tautomerism in 277-benzoxazin-2-ones allows carbon substituents at the 3-position to be reactive toward the NO electrophile. Compounds 227 <1963LA83> and 229 <1963LA93> reacted with the nitrosyl cation to give the derivatives 228 and 230 as shown in Scheme 23. 

The need for well defined polymer species of low polydls-perelty and of known structure arises from the Increasing Interest In structure-properties relationship In dilute solution as well as In the bulk. A great variety of methods have been attempted, to synthesize so-called model macromolecules or tailor made polymers-over the past 20 years. The techniques based on anionic polymerization, when carried out In aprotic solvents, have proved best suited for such synthesis, because of the absence of spontaneous transfer and termination reactions that characterize such systems. The "living 1 polymers obtained are fitted at chain end with carbanionic sites, which can either Initiate further polymerization, or react with various electrophilic compounds, intentionally added to achieve functionalizations. Another advantage of anionic polymerizations is that di-functlonal Initiators are available, yielding linear polymers fitted at both chain ends with carbanionic sites. In this paper we shall review the various utility of anionic polymerization to the synthesis of tailor made well defined macromolecules of various types. 

The terminal carhanionic sites of "living" polymers can be reacted with various electrophilic compounds of yield (o)-functional polymers. Esters, nitriles, acid chlorides, anhydrides, lactones, epoxides, benzyl or allyl halogenides have been used for their high reactivity with metal organic sites, to yield appropriate functions.2 Carbon dioxide is also an efficient reagent to yield terminal carboxylic functions. 

Mechanism-based SAR analysis of different classes and subclasses of chemical carcinogens has revealed some general and specific molecular parameters that can have significant effects on the carcinogenic potential of electrophilic compounds. 

Cell damage induced by chemical carcinogens involves the conversion in the body of a proximate carcinogen (inert) to the ultimate carcinogen that is a reactive electrophilic compound. This ultimate carcinogen may then interact or, more frequently, combine covalently with intracellular components, such as DNA, RNA, phospholipids, or glutathione. 

Another approach to the synthesis of polyimides from chloral derivatives involves the use of dianhydrides of isomeric tetracarboxylic acids containing central carbonyl or 1,1-dichloroethylene groups and two ether bonds as the starting electrophilic compounds [31-33] (Scheme 3.8). 

BULL You re really referring to direct-acting carcinogenic compounds for the most part, the unstable or reactive electrophilic compounds. 

A very useful parameter that would tend to take the results a little out of the emotional realm would be a measure for electrophilic compounds, that is, total electrophilic compounds. That should be easy enough to do with these presumably direct-acting materials. There could be a standard method using nucleophilic trapping agents. 

Azo derivatives of indolizines are readily prepared since the arenediazonium ion is a good electrophile. Compounds of this type are sometimes used as dyes (73AC(R)95>. Another method of preparing azobisindolizines is by reaction of indolizines with tosyl or picryl azides thus compound (33) has been obtained from 2-methylindolizine by this route. Redox characteristics of such compounds have been studied (71LA(752)182, 71LA(752)196). 

Perfluoronaphthyllithium reacts with electrophilic compounds to yield substituted perfluoronaphthalenes [JS] (equation 15)... 

Perflunrinated nitriles are highly electrophilic compounds because of the adjacent electron-accepting substituent Therefore, the addition of amines, alcohols, and mer-captans forming anudines, mutates, and thioimtdates is well-documented [63]. 

Titanium tetrachloride, a very powerful electrophilic compound introduced by Pacsu268 for converting /3-glycosides to a-glycosides and for preparing a-glycosyl chlorides, can be employed for these purposes without causing desulfonylation. Thus, the conversion of methyl... 

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