Haloarenes phenol synthesis

Mechanism of the Pd-Catalyzed Phenol Synthesis from Haloarenes... 

The complete elimination of functional groups is often an undesirable side reaction in organic synthesis, but on the other hand it is a possibility for the recycling of environmentally harmful compounds, for example phenols and haloarenes such as polychlorinated dibenzodioxins (PCDDs or dioxins ). For example, aryl chlorides can be effectively dechlorinated with Pd(0) NPs in tetra-butylammonium salts with almost quantitative conversions also after 19 runs (entry H, Table 1.4) [96]. On the other hand, a C-0 bond cleavage reaction also seems suitable for the fragmentation of sugar-based biomass such as cellulose or cello-biose in that way, sugar monomers and bioalcohol can be derived from renewable resources (entry F, Table 1.4) [164]. 

Acceptor-substituted haloarenes have been successfully used to O-arylate phenols by aromatic nucleophilic substitution (Table 7.14). The most common arylating agents are 2-fluoro-l-nitroarenes, 2-halopyridines, 2-halopyrimidines, and 2-halotriazines. When sufficiently reactive haloarenes are used, the reaction proceeds smoothly with either the arylating agent or the phenol linked to the support. The thallium(III) nitrate catalyzed arylation of phenols with aryl iodides has been used for macrocycli-zations on solid phase [184], Burgess and co-workers have developed a solid-phase synthesis of 3-turri mimetics based on ring-closure by aromatic nucleophilic substitution (Entry 4, Table 7.14 see also Table 10.5). Phenols, alkylamines, and thiols have been successfully used as nucleophiles for this type of macrocyclization [185],... 

The synthetic route is based on the preparation of the M(4-6) and the M(2-4) subunit by intramolecular Sf.jAr cyclizations of suitable precursor peptides with ort/ o-nitro-substituted haloarene residues and a central phenolic unit (Schemes 2 and 4). This concept was originally developed by Zhu and co-workers and applied successfully to the synthesis of cyclic peptides of the vancomycin family, e. g. to the synthesis of K-13 [13]. 

As mentioned in Section 22-4, V-nitrosation of primary benzenamines (anilines) furnishes arenediazonium salts, which can be used in the synthesis of phenols. Arenediazonium salts are stabilized by resonance of the tt electrons in the diazo function with those of the aromatic ring. They are converted into haloarenes, arenecarbonitriles, and other aromatic derivatives through replacement of nitrogen by the appropriate nucleophile. 

---