Aryl ethers, intramolecular complexation

An iridium(lll)-catalyzed tandem Claisen rearrangement-intramolecular hydroaryloxylation protocol has been described that allows the transformation of allyl aryl ethers to dihydrobenzofurans under mild conditions (Scheme 95) <2005TL1237>. An in rl/ -generated PPh3AuOTf complex also proved to be an efficient catalyst for this transformation <2006SL1278>. 

The SjvAr reaction is another attractive method for diaryl ether synthesis, and reactions of o-nitro- and o-cyanofluorobenzenes with phenols were reported . 7r-Complexation of aryl halides with transition metals activates the aromatic nuclei toward S fAr. Segal employed a ruthenium chlorobenzene complex in the poly(aryl ether) synthesis , and the methodology was extensively studied by Pearson, Rich and their coworkers using manganese complex and later iron and ruthenium complexes in natural product synthesis " . The intramolecular substitution of an aromatic chloride with a phenylalanine derivative takes place at room temperature without racemization (equation 27). 

Fagnou and co-workers reported on the use of a palladium source in the presence of different phosphine ligands for the intramolecular direct arylation reaction of arenes with bromides [56]. Later, they discovered that new conditions employing palladium complex 27 promoted the direct arylation of a broad range of aryl chlorides to form six- and five-membered ring biaryls including different functionalities as ether, amine, amide and alkyl (Scheme 7.11) [57]. 

That the second option can also be successfully used has recently been revealed by our synthesis of 2-methoxyphenazine (117) [90]. The reduction of o-bromo-o -nitrodiphenylamine 132 accessible via intermolecular Pd-catalyzed JV-arylation provides the o-amino-o -bromodiphenylamine 133, which can then be cyclized to give 117 in a Pd-catalyzed intramolecular AT-arylation by employing Pd2(dba)3 as the Pd complex and 134 as the phosphine ligand. It should be noted that the outcome of both the intermolecular and the intramolecular AT-arylations heavily depends on the appropriate choice of the Pd complex as well as the phosphine. Ether cleavage leads to 2-hydroxyphenazine (9). 

C-M bond addition, for C-C bond formation, 10, 403-491 iridium additions, 10, 456 nickel additions, 10, 463 niobium additions, 10, 427 osmium additions, 10, 445 palladium additions, 10, 468 rhodium additions, 10, 455 ruthenium additions, 10, 444 Sc and Y additions, 10, 405 tantalum additions, 10, 429 titanium additions, 10, 421 vanadium additions, 10, 426 zirconium additions, 10, 424 Carbon-oxygen bond formation via alkyne hydration, 10, 678 for aryl and alkenyl ethers, 10, 650 via cobalt-mediated propargylic etherification, 10, 665 Cu-mediated, with borons, 9, 219 cycloetherification, 10, 673 etherification, 10, 669, 10, 685 via hydro- and alkylative alkoxylation, 10, 683 via inter- andd intramolecular hydroalkoxylation, 10, 672 via metal vinylidenes, 10, 676 via SnI and S Z processes, 10, 684 via transition metal rc-arene complexes, 10, 685 via transition metal-mediated etherification, overview,... 

Mechanistically, this new insertion-CI-Diels-Alder hetero domino sequence can be rationalized as follows (Scheme 64) After the oxidative addition of the aryl halide 115 or 118 to the in situ generated Pd(0) species the arylpalladium halide 120 intramolecularly coordinates and inserts into the tethered triple bond via a syn-carbopaUadation to furnish cyclized vinylpalladium species 121 with a p-acceptor substitution in a stereospecific fashion. Transmetallation of the in situ generated copper acetylide 122 gives rise to the diorganylpalladium complex 123 that readily undergoes a reductive elimination and liberates the electron poor vinylpropargylallyl ether 124. The triethylamine catalyzed propargyl-allene isomerization furnishes the... 

Multiple intramolecular ring closures of aryl-substituted unsaturated long chain alcohols, acids, acid chlorides and ethers in the presence of Friedel-Crafts catalysts have been extensively employed to synthesize polynuclear hydroaromatic hydrocarbons and polycyclic ketones. This is illustrated by two examples shown in equations (112) and (113). The application of stereospecific cycloalkylations in approaching the synthesis of complex organic molecules has been reviewed by Barclay. ... 

---