As an ambident nucleophile

Santaniello et al.125 have N-alkylated pyrrole and indole (71) in the presence of crown-ether catalysts. The indolyl anion also behaves as an ambident nucleophile alkylation occurs at nitrogen and at C-3.126... 

The two possible valence-bond structures of the enolate anion, 7a and 7b, show that the anion should act as an ambident nucleophile—a nucleophile with nucleophilic properties associated with both carbon and oxygen. The addition step in the aldol reaction therefore may be expected to take place in either of two ways The anion could attack as a carbon nucleophile to form a carbon-carbon bond, 8, leading ultimately to the aldol 9, or it might attack as an oxygen nucleophile to form a carbon-oxygen bond, thereby leading to the hemiacetal 10. By this reasoning, we should obtain a mixture of products 9 and 10. However, the aldol 9 is the only one of these two possible products that can be isolated ... 

The lithium salt of diethyl 2-propenylphosphonate behaves as an ambident nucleophile in reactions with a variety of electrophilic reagents. In reaction with methyl methacrylate, the intermediate formed in the lirsl step (conjugate addition at the y-carbon of the phosphonate) has a carbanionic center developed at C-5. The second step involves intermolecular conjugate addition to a second molecule of methyl methacrylate, yielding an intermediate capable of the final 1,6-cyclization to produce a phosphonylated polyfunctionalized derivative of cyclohexane in good overall yield (60%, Scheme 8.63). ... 

In its reactions, the indolyl anion behaves as an ambident nucleophile the ratio of N- to P-substitution with electrophiles depends on the associated metal, the polarity of the solvent, and the nature of the electrophile. Generally, the more ionic sodio and potassio derivatives tend to react at nitrogen, whereas mag-nesio derivatives have a greater tendency to react at C-3 (see also 20.1.1.4), however, reaction of indolyl Grignards in HMPA leads to more attack at nitrogen. Complimentarily, more reactive electrophiles show a greater tendency to react at nitrogen than less electrophilic species. 

Aniline as an Ambident Nucleophile Normal versus Superelectrophiles... 

Since the cyanide anion is an ambident nucleophile, isonitriles R—NC may be obtained as by-products. The reaction pathway to either nitrile or isonitrile can be controlled by proper choice of the counter cation for the cyanide anion. 

Another premise cannot be excluded and will be investigated eventually. As in the case of cyanide ion, isothiocyanate ion may be a precursor in the biosynthesis of some marine isothiocyanates. Like cyanide, thiocyanate ion is an ambident nucleophile. Specific incorporation of this ion by a carbocationic site... 

Hydroxylamine derivatives are ambident nucleophiles. For example, N-benzylhy-droxylamine functions as an N-nucleophile in the Ir-catalyzed allylic substitution, while N-Boc-hydroxylamine yields mixtures of the N- and O-substituted products in Ir- as well as Pd-catalyzed allylic substitutions. Accordingly, either O- or N,0-protected hydroxylamine derivatives need to be used as nucleophiles [63]. 

Alkyl halides are often used as substrates instead of alcohols. In such cases the salt of the inorganic acid is usually used and the mechanism is nucleophilic substitution at the carbon atom. An important example is the treatment of alkyl halides with silver nitrate to form alkyl nitrates. This is used as a test for alkyl halides. In some cases there is competition from the central atom. Thus nitrite ion is an ambident nucleophile that can give nitrites or nitro compounds (see 0-60).731 Dialkyl or aryl alkyl ethers can be cleaved with anhydrous sulfonic acids.732... 

The properties of dimethyl carbonate, (MeO)2CO, as an ambident electrophile have been investigated by analysis of the products of its reaction with various nucleophiles having different hard-soft character. Results were in good agreement with the Hard-Soft Acid-Base theory, hard nucleophiles attacking the hard C=0 group and soft nucleophiles the soft Me group (Scheme ll).37... 

Apart from the above two major general reaction pathways, there are some further possibilities for instance, [bis(trifluoroacetoxy)iodo]benzene reacts as an ambident electrophile and is attacked by hard nucleophiles at its carbonyl carbon, whereas iodylarenes may react similarly from carbon rather than iodine. Alkynyl iodonium salts are actually tetraphilic electrophiles, whereas iodosylbenzene reacts also as a nucleophile from oxygen. Diaryl iodonium salts serve as arylating reagents, mostly homolytically other iodonium salts transfer groups such as perfluoroalkyl, vinyl, alkynyl or cyano to several nucleophiles in various ways. 

As already discussed in Section 4.19.2.2.1 hydroxyl derivatives of thiazole are tautomeric, according to Scheme 127, the oxo forms usually being the most stable. The interconversion of the hydroxyl and carbonyl forms proceeds under acid or base catalysis. This protomeric behavior of the thiazolinones corresponds to an ambident nucleophilic reactivity which is most marked for the conjugate anion arising in basic medium. 

Enolates are nucleophiles, and as such they react with many electrophiles. Because an eno-late is resonance stabilized, however, it has two reactive sites— the carbon and oxygen atoms that bear the negative charge. A nucleophile with two reactive sites is called an ambident nucleophile. In theory, each of these atoms could react with an electrophile to form two different products, one with a new bond to carbon, and one with a new bond to oxygen. 

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