Phenyl group displacement

Trimethylgermyl substituents in aromatic compounds are easily removed with halogen, yielding the corresponding aryl halide, as shown in reaction 8119. Another example of phenyl group displacement was carried out with bromine as in reaction 2 (see end of Table 2)64. 

Although a sulfhydryl group generally is not converted to an 5-phenyl thioether, the conversion can be accomplished through the use of a Pd-catalyzed arylation with an aryl iodide. Thiophenol can be used to introduce sulfur into molecules by simple displacement or by Michael additions, and thus, the phenyl group serves as a suitable protective group that can be removed by electrolysis (—2.7 V, DMF, R N X-). ... 

Alkylaryldichlorogermanes produce substituted cyclogermanes. In the case shown in reaction 9, three of the four possible configurations of the tetragermane product 29 are formed, but none is all-c/s. It is possible to carry out an electrophilic displacement of the phenyl groups to form the 1,2,3,4-tetrachloro derivative 30, which is aW-lrans, the configuration of 29 notwithstanding120. 

In the case where R = Ph, a bromine cleavage of one phenyl group of 29 allows, by subsequent nucleophilic displacement of the resulting bromide, the preparation of several other alkyl or phenyl-substituted derivatives of germanium65. 

A more recent synthesis for (14-9) takes quite a different course. The first step comprises the displacement of one of the halogens in 1,4-dibromobenzene by the alkoxide from A-2-hydroxyethylpyrrolidine (15-2) in the presence of 18-crown ether to afford (15-3). Condensation of the lithium salt from (15-3) with 6-methoxy-tetralone (15-4) followed by dehydration of the initially formed carbinol give the intermediate (15-5), which incorporates the important basic ether. Reaction of that compound with pridinium bromide perbromide leads to the displacement of the vinylic proton by halogen and the formation of bromide (15-6). Condensation of that product with phenylboronic acid in the presence of a tetrakistriphenyl-phosphine palladium catalyst leads to the coupling of the phenyl group by the formal displacement of bromine. The product (14-9) is then taken on to lasoxifene (14-11) as above [16]. 

An interesting amination, apparently involving displacement of a phenyl group in the benzo[c]l,7-naphthyridine (132)147 has been reported. 

Diphenyl phosphorochloridate is one of the most widely employed phosphorylating reagents for the preparation of phosphomonoesters (Scheme 3.17a).94 The chloride acts as a leaving group that can be displaced by hydroxyls. The phenyl groups act as protecting groups that... 

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