Nucleophihc attack

The acetaldehyde-forming step (eq. 7) involves nucleophihc attack by hydroxide or water on a coordinated Pd olefin complex followed by P-hydride elimination. 

Thiol—Disulfide Interchange Reactions. The interchange between thiols and disulfides has been reviewed (50). This reaction is base-catalyzed. It involves the nucleophihc attack of a thiolate ion on a disulfide. This is shown in equations 35, 36, and 37. 

Perfluorinated epoxides, which are generally susceptible to C-O cleavage during nucleophihc attack, are cleaved by lithium alummum hydnde Of the available examples, reduction of epoxides from two types of internal olefm to give alcohols IS shown [4S] (equations 37a and 37b)... 

Because of thetr electron deficient nature, fluoroolefms are often nucleophihcally attacked by alcohols and alkoxides Ethers are commonly produced by these addition and addition-elimination reactions The wide availability of alcohols and fliioroolefins has established the generality of the nucleophilic addition reactions The mechanism of the addition reaction is generally believed to proceed by attack at a vinylic carbon to produce an intermediate fluorocarbanion as the rate-determining slow step The intermediate carbanion may react with a proton source to yield the saturated addition product Alternatively, the intermediate carbanion may, by elimination of P-halogen, lead to an unsaturated ether, often an enol or vinylic ether These addition and addition-elimination reactions have been previously reviewed [1, 2] The intermediate carbanions resulting from nucleophilic attack on fluoroolefins have also been trapped in situ with carbon dioxide, carbonates, and esters of fluorinated acids [3, 4, 5] (equations 1 and 2)... 

Unsaturated fluorocarbons are much more reactive toward nucleophiles than then hydrocarbon counterparts owing to fluorme s ability to both stabihze carban ions and mductively increase the electrophihcity of multiple bonds and aromatic nngs Nucleophihc attack dominates the chemistry of unsaturated fluorocarbons, and the role of fluonde ion in fluorocarbon chemistry is analogous to that of the proton in hydrocarbon chemistry [129] Like the related electrophilic reactions for hydrocarbons, there are fluonde-promoted isomenzations and dimenzations (equation 9), oligomenzations (equation 10), additions (equation 11), and amomc Fnedel-Crafts alkylations (equation 12) that all proceed via carbamomc intermediates [729 7 7]... 

In the case of tertiary N-ethylamine derivatives the N-ethyl group is first selectively oxidized by p-chloranil to an enamino group which then condenses with excess p-chloranil to a blue aminovinylquinone derivative [7]. Secondary N-ethyl derivatives do not yield blue aminovinylquinone derivatives they probably react directly with chloranil by nucleophihc attack at one of the four chlorine atoms to yield aminoquinones of other colors [7], It has also been suggested that some classes of substances react to yield charge transfer complexes [1, 5, 8, 12],... 

Pd(II)-catalyzed intramolecular nucleophihc attack by an oxygen [61-63] or a nitrogen [64-68] atom followed by alkoxycarbonylation has also been reported, and has allowed an easy entry to useful heterocyclic compounds (Scheme 12). 

The last reaction in Scheme 13 becomes possible when the sulfide has a CH2 or CH fragment, adjacent to the sulfur atom whose protons are getting more acid when the molecule is oxidized. Electron-withdrawing groups (EWGs) increase the ease of deprotonation of this site even more. Thus, a-MeO-, a-AcO-, and a-F-sulfides were prepared (Eq. 9) [67-70]. When the nucleophihc attack is sterically hindered or a-protons are absent, products acetoxylated in the phenyl ring are... 

Nucleophihc attack of methoxide ion on olefinic and acetylenic groups of suitable unsaturated phosphine complexes of platinum(II) takes place to give cyclic, a-bonded complexes. This reaction appears to occur whether or not the unsaturated group is coordinated to the metal (22). But-3-enyl diphenylphosphine forms a chelate complex with platinum(II) chloride which on treatment with sodium hydrogen car-... 

It was reported earher that the oxidation of a sulfoxide to a sulfone involves either an initial nucleophihc attack of the nucleophilic oxidant or an electrophihc attack by an electrophilic oxidant. It is noteworthy that the oxidation of p-tolyl methyl, phenyl methyl and p-chlorophenyl methyl sulfoxides to the sulfones using the sulfonylperoxy intermediate 51 appears to be electrophihc, namely the relative reactivity order was p-tolyl methyl > phenyl methyl > p-chlorophenyl methyl sulfoxide based on competitive oxidations. 

The reaction of lucigenin and different nucleophiles was first studied by Janzen and collaborators. In highly alkaline media, the formation of lucigenin pinacol (41) resulting from the nucleophihc attack of hydroxyl ion at position 9 of lucigenin is observed ... 

N-Metalated azomethine ylides generated from a-(alkylideneamino) esters can exist as tautomeric forms of the chelated ester enolate (Scheme 11.8). On the basis of the reliable stereochemical and regiochemical selectivities described below, it is clear that the N-metalated tautomeric contributor of these azomethine ylides is important. Simple extension of the above irreversible lithiation method to a-(alkylideneamino) esters is not very effective, and cycloadditions of the resulting lithiated ylides to a,(3-unsaturated carbonyl compounds are not always clean reactions. When the a-(alkylideneamino) esters bear a less bulky methyl ester moiety, or when a,(3-unsaturated carbonyl compounds are sterically less hindered, these species suffer from nucleophihc attack by the organometalhcs, or the metalated cycloadducts undergo further condensation reactions (81-85). 

Catalyst conditions very similar to those employed in Eq. 42 and Scheme 12 were used recently by Lloyd-Jones, Booker-Milburn, and coworkers to achieve Pd-catalyzed diamination of conjugated dienes with urea nucleophiles (Eq. 44) [181], Both dioxygen and BQ were evaluated as oxidants, and BQ proved to be significantly more effective (Eq. 44). The beneficial effect of BQ probably arises from its ability to promote nucleophihc attack on the intermediate Tt-allyl palladiiun complex (see below. Sect. 4.4). This hypothesis is supported by the observation that the oxidative amination of styrene with urea, which does not undergo the second nucleophilic attack, proceeds equally effectively with both O2 and BQ as the oxidant (Eq. 45). 

SCHEME 8. Schematic representation for the chelate-controlled addition of an organometaUic reagent (M—R) to the carbonyl group of a chiral a-alkoxy carbonyl compound (17). Two diastere-omers 18 with different orientation of R with respect to CH2R can be obtained. The syn diastereomer is obtained when the nucleophihc attack of R takes place on the same face of the plane, defined by the carbonyl group and the R-substituted carbon atom, where CH2R is located in the chelate complex... 

There is nucleophihc attack by external water (reaction 3) at a neutral Pd(C2H4) species to give a palladium hydroxyethyl intermediate. The following displacement of Cl by water is rate-limiting. The Pd—CH2CH2OH complex decomposes by j8-H elimination the resulting vinyl alcohol isomerizes to acetaldehyde. 

FIGURE 14. Structure of E coli amine oxidase active site in the equilibrium turnover complex. Interactions and labelling as in Figure 12 except that the reduced form of the cofactor is labelled TPR and carries a nitrogen at the 5-position. The aldehyde product, labelled Prod, is retained in the channel to the enzyme surface. Water W4 is positioned for nucleophihc attack on C5 of the cofactor and W2 is retained as a link in a proton shuttle from 04 to dioxygen. 

A problem with equation (11) is the separation of W(CO)sC8 from W(CO)e formed in side reactions, since these compounds have very similar properties. Coordinated C8 is reactive toward an electrophilic attack at sulfur and a nucleophihc attack at carbon (equations 12 and 13). The... 

The chelated phosphoramidate (22) is formed as an intermediate in the reaction of [Co(NH3)5(DNPP)]+ in alkaline solution, through intramolecular nucleophihc attack of a deprotonated m-ammine (Scheme 1). Similar reactivity is observed in the monodentate pyruvate complex [Co(NH3)50C(0)C(0)CH3] +, where the imino carboxylate chelate (23) is formed at pH > 12. ... 

Dehydration of (2-hydroxymethyl-1,3-butadiene)iron complexes or (hydroxymethyltrimethylenemethane)iron complexes with fluorosulfonic acid/liquid sulfur dioxide generates the corresponding (cross-conjugated dienyljiron cations (194) (equation 72). The H and NMR spectral data for these cations favor an " -TMM-methyl cationic structure (282) over an ) " -isoprenyl cationic stmcture (283). These cations react with water or alcohols to afford butadiene products via nucleophilic attack at C-5. As indicated earlier (Section 6.1.1), the cross-conjugated dienyl cations are believed to be intermediates in the substitution of (193) with weak carbon nucleophiles (Scheme 53). In these cases, nucleophihc attack occurs on C-4 to give predominantly TMM products. ... 

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