Oxidants electrophilic

Lavilla et al. have reported several stereocontrolled oxidative electrophilic additions to A-alkyl-l,4-dihydropyridines 34 leading to the synthesis of 3-halo-2-substituted-l,2,3,4-tetrahydropyridines 67 (98JOC2728). Adding a stoichiometric amount of iodine or NIS (A-iodosuccinimide) to a methanolic solution of 1 -methy 1-... 

Unsubstituted benzobicyclo[2.2.2]octatriene 76a bearing two methoxycarbonyl groups at the and C3 positions exhibited strong anti preference (with respect to the benzene moiety) with two oxidative electrophilic reagents, m-chloroperbenzoic acid (mCPBA) and osmium tetroxide. 

Oxidative electrophilic activation of a, f-unsaturated phenylsulfides, carried out in an AcOH/AcONa solution results in products of the addition of a nucleophile to the multiple bonds, a,y3-diacetoxysulfides or, as a result of a further oxidation, that eliminates the PhS group, in a-acetoxy ketones (Scheme 23) [89]. 

The oxidation of 3,6-dehydrohomoadamantane (52) with NO+BF4, photo-excited tetracyanobenzene, and under anodic conditions has been found to involve a common radical cation intermediate. The study has shown that the activation of propellane cTc-c bonds with strong oxidizing electrophiles occurs by a sequence of single-electron transfer steps. These findings are supported by ab initio computations showing that the isomeric radical cations can equilibrate with low barriers and lead to a common product. ... 

These compounds are less common than indole (benzo[ ]pyrrole). In the case of benzo[i>]furan the aromaticity of the heterocycle is weaker than in indole, and this ring is easily cleaved by reduction or oxidation. Electrophilic reagents tend to react with benzo[Z ]furan at C-2 in preference to C-3 (Scheme 7.21), reflecting the reduced ability of the heteroatom to stabilize the intermediate for 3-substitution. Attack in the heterocycle is often accompanied by substitution in the benzenoid ring. Nitration with nitric acid in acetic acid gives mainly 2-nitrobenzo[Z ]furan, plus the 4-, 6- and 7-isomers. When the reagent is in benzene maintained at 10 °C, both 3- and 2-nitro[ ]furans are formed in the ratio 4 1. Under Vilsmeier reaction conditions (see Section 6.1.2), benzo[Z ]furan gives 2-formylbenzo[6]furan in ca. 40% yield. 

In benzo- and phenyl-pyridines and in phenylpyridine 1-oxides, electrophilic substitution usually takes place in the benzene ring. In benzo-pyridones, -pyrones and -pyridine A-oxides, electrophilic substitution often occurs in either the benzene or the heterocyclic ring depending on the conditions sometimes mixtures are formed (see Section 3.2.3.2.1). 

In 1,3-type N-oxides, electrophiles preferentially attack at the 2-position since attack at this position renders an intermediate 23 with one positive charge mesomerically delocalized to the pyrrole nitrogen atom. Attack at C4 or C5 would give rise to intermediates like 25 without such mesomeric delocalization of their positive charge (Scheme 5). 

A similar mechanism (Eq. 4) is operative in reactions of saturated hydrocarbons with closed-shell oxidizing electrophiles (E = Haln+, NOz+, etc.) where the H-trans-fer from a C-H bond is accompanied by an ET through the linearly H-coupled fragment (H-coupled electron transfer) [13]. The hydrocarbon part of the transition structures resembles the respective radical cation (that for the reaction of adamantane with Cl7+ is shown (6) in Scheme 2) [13]. 

LDH-WC>4 has also been applied for oxidative bromination of unsaturated hydrocarbons (367). In a first step, W on LDH catalyzes the oxidation of Br with H202. Subsequently, the resultant bromonium species (Br+, which could be equilibrated with species such as HOBr or Br2) react rapidly with the target molecules. An advantage of the oxidative electrophilic bromination is that the active bromine is formed in situ in a controlled way there is no direct contact with Br2. Moreover, the bromination is performed under mild conditions such as room temperature, atmospheric pressure, and near neutral pH. Indeed, the FI ) 11-WO -catalyzed bromination mimics the enzymatic activity of bromoperoxidases not only formally but also organizationally and mechanistically. For example, indene is bromohydroxylated almost quantitatively with NH4Br and H2O2 in a water-2-methyltetrahydrofuran solvent mixture (368) ... 

The powerful 1-electron oxidant, cobalt(III) trifluoroacetate in trifluoroacetic acid, readily oxidizes ethylene at ambient temperatures to afford ethylene glycol ditrifluoroacetate.217 The oxidizing properties of cobalt (III) trifluoroacetate in trifluoroacetic acid are probably due to the formation via dissociation of cationic species, such as Co+(02CCF3)2, which are very strong oxidants (electrophiles). The following electron transfer mechanism is suggested for the oxidation of ethylene ... 

Enhancement by strong acids such as TFA is a general feature of oxidations with metal acetates. Metal trifluoroacetates in TFA are much more powerful oxidants (electrophiles) than the corresponding acetates in acetic acid. Activation of the metal oxidant in TFA has been observed with co-balt(III)217 249,259,27S 276 manganese(III),237,275 lead(IV),277-281 thallium-(III),282-287 cerium(IV),288 289 and copper(II).290 Similarly, the electrophilic properties of copper(I)291 and mercury(II)292 acetates are strongly enhanced by replacement of acetate by trifluoroacetate. It has been proposed217,276 that the potent oxidizing properties of Co(III) trifluoroacetate are due to ionization to the cationic Co(III) species,... 

A diastereoselective ewrfo-cyclization into an oxidatively generated oxocarbenium ion was a key step in a formal synthesis of leucascandrolide A. Exposing 56 to CAN provided cw-tetrahydropyran 57 in high yield and with excellent stereocontrol (Scheme 3.20). This transformation provides further evidence that oxidative electrophile formation is tolerant of several functional groups and can be applied to complex molecule synthesis. The synthetic sequence also utilized a Lewis acid mediated ionization reaction to form an oxocarbenium ion in the presence of the homobenzylic ether (58, 59), illustrating that two carbocation precursors that ionize through chemically orthogonal conditions can be incorporated into the same structure. 

Although the water molecule is exceptionally rugged, it is a reductant (nucleophile) of strong oxidants (electrophiles) (equations 6 and 7) and an oxidant (electrophile) of strong reductants (nucleophiles) (equations 8 and 9). 

Although the water molecule is exceptionally rugged, it is a reductant (nucleophile) of strong oxidants (electrophiles). 

Iodine potassium iodide Oxidative electrophilic substitution with thioureas... 

To become thiosulfate, the central sulfur in the thiosulfite needs to get oxidized. Electrophilic fluorination, as depicted below, might just provide a way for that to happen ... 

This review is devoted to an overview of phenol dearomatization and its application in natural product synthesis through the use of a special class of phenolophile reagents that has attracted much attention in recent years, the hypervalent iodine reagents. These polyvalent iodine compounds, also called iodanes, are oxidizing electrophiles that can mediate a wide number of diverse chemical transformations not only of (hetero)aromatic compounds, but also of inter alia alkenes, alkynes, alcohols, sulfides, amines and amides, (enolizable) carbonyl... 

The SET oxidation reactions of a range of tricyclic compounds and [3.3.n]propellanes with a range of oxidizing electrophiles (e.g. N02 BF4 ) have been investigated computationally at the BLYP/6-311- -G //BLYP/6-31G non-hybrid density functional level. The low ionization potentials and high proton affinities of the strained propellanes are used to rationalize the SET reactions. 

In all these reactions of nucleophiles and electrophiles with metal complexes, electron transfer from a reducing nucleophile or to an oxidizing electrophile competes and sometimes inhibits the reaction. 

Since isobutene has a double bond in its molecular structure, it can undergo different chemical reactions typical for olefins and yield a great variety of products. Some examples of these reactions are hydrogenation, oxidation, electrophilic addition, polymerisation and hydration (van Leeuwen et al. 2012). 

---