Phenoxides reaction with

Displacement of a tertiary amine from a quaternary (eq. lb) iavolves the attack of a nucleophile on the a-carbon of a quaternary and usually competes with the Hoffman elimination (173). The counterion greatiy iafluences the course of this reaction. For example, the reaction of propyltrimethylammonium ion with hydroxide ion yields 19% methanol and 81% propylene, whereas the reaction with phenoxide ion yields 65% methoxybenzene and 15% propylene (174). 

Fig. 7-2. Potential energy E as a function of the reaction coordinate for reactions of the P-nitrogen of arenediazonium ions with nucleophiles yielding (Z)- and (is)-azo compounds, a) Reactant-like transition states (e. g., reaction with OH) b) product-like transition states (e. g., diazo coupling reaction with phenoxide ions product = cyclohexadienone-type o-complex (see Sec. 12.8).

The chloro group of 6 is now highly activated toward nucleophilic aromatic substitution, facilitating reaction with phenoxide. Subsequent catalytic reduction in the presence of LiOH produces amino acid 7. Next, treatment with butanol and sulfuric acid not only forms the butyl ester but monoalkylates the amino function. Saponification of the ester group leads to bumetanide (8), a diuretic agent possessing 40-fold greater activity in healthy adults than furosemide. ... 

There have been several studies utilizing the ability of 4,6-dinitrobenzofuroxan (DNBF) to act as a super-electrophile. It has been shown that the initial product of its reaction with phenoxide ions is the O-bonded adduct (29), although this rearranges to give die C-bonded adduct.117 The reaction of DNBF with ethyl vinyl ether yields a dihydrooxazine A -oxidc cycloadduct as a mixture of two diastereoisomers, and in the presence of excess ether a di-adduct (30) is formed.118 Rate constants have been reported for the reaction of DNBF with 3-methoxythiophene in DMSO-water mixtures. The reaction results in a er-adduct which is the product of Se-At substitution in the thiophene, and the results were used to probe the carbon basicity of the thiophene derivative.119... 

Separation of the p-nitro-substituted aryl halide and reaction with phenoxide ion complete the synthesis. 

Nitrogen [186], oxygen [187], and sulfur nucleophiles [170] also act as nice Michael donors in the tandem MCI reactions [Eq. (106)]. The a-oxyalkylidene carbene 116, generated by the reaction with phenoxide anion, shows a high selectivity for 1,5-insertion to the aromatic over the aliphatic C-H bonds to give the benzofuran. 

These reactions appear to be restricted to strongly basic nucleophiles, as we found no reaction with phenoxides and thio-phenoxides. This lack of reactivity is attributed to the reversibility of the nucleophilic substitution, promoted by the increased leaving group ability of the nucleophile, e.g. 

Carbenes also add to other nucleophiles, such as hydroxide, thiolate, and phenoxide. The reaction with phenoxide is the classic Reimer-Tiemann reaction. 

This reaction is analogous to 10-7. It may be acid (including Lewis acids ), base, or alumina catalyzed, occur with electrolysis, and may occur by either an SnI or 8 2 mechanism. Catalysts, such as [Rh(CO)2Cl]2, TiCla (OTf), Fe(C104)3, Cu(BF4)2 m H2O, or BiCla, have been used. (3-Cyclodextrin has been used to promote the reaction with phenoxides in aqueous media. Many of the p-hydroxy ethers produced in this way are valuable solvents, for example, diethylene glycol and Cellosolve. Reaction with thiols leads to hydroxy thioethers. The reaction of alcohols with aziridines leads to p-amino ethers, and reaction with thiols gives p-amino thioethers. " It has been shown that ringopening of aziridines by phenols is promoted by tributylphosphine. ... 

Figure 6.32 Successes and failure of carbonate protection in an attempt to make aryl P-mannobiosides. The formation of the cyclic orthocarbonate must be entirely due to the complex phosphine oxide leaving group in the Mitsunobu reaction, since 4,6-di-O-acetyl-a-D-mannopyranosyl bromide 2,3-carbonate gave the expected aryl P-mannosides on reaction -with phenoxides. ...

Coupling reactions with phenoxides. Influence of electronic character and effect of ion-pair dissociation. 

We will now give a more detailed analysis of the available data, using the following four cases 1. Coupling reactions with phenoxides influence of the electronic character and the effect of ion-pair dissociation. 2. Coupling reactions with alkoxides influence of solvation. 3. Nucleophilic substitution at silicon by carbon nucleophiles. 4. Reduction reactions by alanes, AlH Y3 n. 

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