Nucleophilic substitution process

Polyetherimide Resins. Polyetherknide resins (PEI) (7) were commercialized during the 1980s (see Polyimides). They ate produced by an unusual nucleophilic substitution process ... 

Table S.16 presents data on some representative nucleophilic substitution processes. The first entry illustrates the use of 1-butyl-l-r/p-bromobenzenesulfonate to dononstrate at primary systems react with inversion, even under solvolysis conditkms in formic acid. The observation of inversion indicates a concerted mechanism in fids weakly nucleophilic solvent.

A variation of the aromatic nucleophilic substitution process in which the leaving group is part of the entering nucleophile has been developed and is called vicarious nucleophilic aromatic substitution. 

Nucleophilic substitution by ammonia on a-halo acids (Section 19.16) The a-halo acids obtained by halogenation of carboxylic acids under conditions of the Hell-Volhard-Zelinsky reaction are reactive substrates in nucleophilic substitution processes. A standard method for the preparation of a-amino acids is displacement of halide from a-halo acids by nucleophilic substitution using excess aqueous ammonia. 

Much study has been devoted to the mechanisms of these reactions, but firm conclusions are still lacking, in part because the mechanisms vary depending on the metal, the R group, the catalyst, if any, and the reaction conditions. Two basic pathways can be envisioned a nucleophilic substitution process (which might be S l or Sn2) and a free-radical mechanism. This could be an SET pathway, or some other route that provides radicals. In either case, the two radicals R- and R would be in a solvent cage ... 

The problem of the thermally induced polymerization reaction of partially or completely substituted cyclophosphazenes has been considered in the past by several authors [355-357], and more recently by H. R. AUcock [358]. This is because of the ease of synthesizing these substrates, the possibihty of preparing structurally regulated poly(organophosphazenes), and the lack of any additional nucleophilic substitution processes on the poly(organophosphazenes) obtained by the ROP process of fully saturated trimers. 

German ED, Dogonadze RR. 1974. The kinetics of nucleophilic substitution processes in the alkyl halides. Part A—theory. Int J Chem Kin 6 457-466, and references therein. 

Scheme 4.6. Electrochemically catalysed nucleophilic substitution process.

Thermolysis of 78a in methanol yielded compounds 86 (R = OMe and R = H) in a 1 1 ratio (77JA633). In this case, the nucleophilic substitution process becomes more important because of the increased electrophilicity of the carbene. 

The amide derived from the carboxylic acid in Ugi adducts is in most cases tertiary, and therefore it cannot serve as nucleophilic partner in post-condensation transformations, unless a post-Ugi rearrangement converts it into a free amine [52, 54]. An exception is represented by Ugi adducts derived from ammonia, which give rise to two secondary amides, each of them potentially involved, as nucleophile, in nucleophilic substitution processes. Four competitive pathways are in principle possible (N- or 0-alkylations of the two amides), and the reaction is mainly driven by the stability of the formed rings. In the example shown in Fig. 12, 0-alkylation of the carboxylic-derived amide is favoured as it generates a 5-membered ring (oxazoline 62), while the alternative cyclization modes would have formed 3- or 4-membered rings [49]. When R C02H is phthalic acid, however, acylaziridines are formed instead via Walkylation [49]. In both cases, the intramolecular 8 2 reactions takes place directly under the Ugi conditions. 

Banfi L, Basso A, Riva R (2010) Coupling isocyanide-based multicomponent reactions with ahphatic or acyl nucleophilic substitution processes. Synlett 23-41... 

The refers to a nucleophilic substitution process where some nucleophile attacks an electrophile and substitutes for some part of the electrophile. The E refers to an elimination process where the nucleophile attacks an electrophile and causes the elimination of something. The 1 and 2 refer to the order of the reaction. A 1 (first order) means only one molecule determines the rate of the reaction, whereas a 2 (second order) means that a combination of two molecules determines the rate of the reaction. In many cases, two or more of these mechanisms are competing and more than one product may result. 

The triflate 125 is formed from the hydroxy precursor (Equation 131) and undergoes a variety of nucleophilic substitution processes <2006TL4437>, including Suzuki and Stille couplings (Equations 132 and 133, respectively). Amination of 125 with aliphatic amines occurs under thermal conditions, using either conventional or microwave heating (Equation 134), but the reactions of 125 with less reactive amines require palladium catalysis (Equation 135). 

In the section on nucleophilic substitution processes we saw that the SN2 process is simply a single electron shift coupled with bond reorganization. The question we wish to consider in this section is how the CM model treats standard electron transfer reactions such as (89) and how the model relates to the Marcus theory, now universally accepted for treating such processes (Marcus, 1964, 1977). 

Two modes of addition may be depicted for the reaction of adds to epoxides, corresponding formally to uncatalyzed and acid-catalyzed nucleophilic substitution processes. These moy be represented as in Eq. (696). Although the situation ia probably more complicated in actual fact, the simplified picture presented here will suffice within the framework of the Farker-Jsaacs modal for epoxide reactions.1201 if... 

Electrophilic substitution allows replacement of a proton or another electrofuge with a different group and is the most-used process for functionalizing aromatic rings, whereas nucleophilic substitution is often considered to be more difficult or to require special substituents or reaction conditions. Prior to 1970, only two significant classes of nucleophilic substitution processes on aromatic rings had been... 

A comparative study of the effects of Li+ and K+ on the ethanolysis of a series of X-phenyl methyl phenyl phosphinates (97) has revealed that Eto- is < MOEt, contrary to the generally observed reactivity order in nucleophilic substitution processes.93... 

On the contrary, in the case of 1-iodonorbomane (a tertiary halide), the result of the reaction with trimethylstannyl reagents (Me3SnM, M = Li, Na), both in the absence and in the presence of trapping agents, confirmed that the nucleophilic substitution process is governed by competition between polar and radical mechanisms133. 

Af-Methyl-jV-(l-methylpropyl)-l(2-fluoro-5-nitrophenyl)isoquinoline-3-carboxamide, 323, possessing high affinity and selectivity for PBBS (peripheral-type benzodiazepine binding sites)312 in living man, has been labelled313 with n.c.a. fluorine-18, obtained via lsO(p, n)18F nuclear reaction, by an aromatic nucleophilic substitution process (equation 139). (n.c.a. = no carrier added)... 

Fluorinated dienes, like fluoroalkenes, are very susceptible to nucleophilic attack [90, 91] some examples of nucleophilic substitution processes are given in Table 7.17. Examples of rearrangements and other reactions are also listed. An early demonstration that... 

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