Aryl derivatives bond formation

Only few examples are present in the literature on aryl-N bond formation through the SrjjI mechanism. 2-Bromomesitylene has been found to undergo bromine substitution by amide anion affording 2-aminomesitylene in 70% yield, with only a small amount of dehalogenated derivative (see Scheme 4.33). The success of the reaction in this case was probably due to the precluded formation of benzyne intermediates from this reagent [179],... 

The reaction sequence starts from tetrazolyldiazonium salt 42 prepared from aminotetrazole 41 by diazotation. This compound when reacted with arylformylacetonitrile 43 leads to the intermediate formation of the condensation product 44, which easily undergoes ring closure to 45. This tetrazolo[5,l-z][l,2,4]triazine compound, however, forms an equilibrium with the valence bond isomeric azide 46, which can participate in a different ring closure than the reverse route, and yields the tetrazolo[l,5-A][l,2,4]triazine product 47. The reaction was carried out with a series of various aryl derivatives and proceeded in good to excellent yields (68-87%). 

Fluorosilylsubstituted aryl derivatives were found to be useful reagents for carbon-carbon bond formation via palladium-catalyzed cross-coupling with aryl halides in the presence of fluoride anions as Si—C bond activator in dimethylformamide (DMF), as well as rhodium-catalyzed 1,4-addition to a, 3-unsaturated ketones in the presence of a fluoride anion source (Equation 14.11) [66, 69, 70],... 

TV-substituted methylenephthalimide derivatives served as the starting material for the preparation of a series of tetracyclic systems. The intramolecular Heck reaction of these compounds (4.10.) led in each case to the formation of a carbon-carbon bond between the exocyclic carbon atom of the olefin bond and the aryl moiety. The formation of five, six and seven membered rings was achieved with near equal efficiency, enabling the preparation of some isoindolobenzazepine alkaloids.11... 

Recent progress on the use of hypervalent iodine reagents for the construction of carbon-het-eroatom (N, O, P, S, Se, Te, X) bonds is reviewed. Reactions of aryl-A3-iodanes with organic substrates are considered first and are loosely organized by functional group, separate sections being devoted to carbon-azide and carbon-fluorine bond formation. Arylations and alkenyla-tions of nucleophilic species with diaryliodonium and alkenyl(aryl)iodonium salts, and a variety of transformations of alkynyl(aryl)iodonium salts with heteroatom nucleophiles are then detailed. Finally, the use of sulfonyliminoiodanes as aziridination and amidation reagents, and reactions of iodonium enolates formally derived from monoketones are summarized. 

The use of hypervalent iodine reagents for heteroatom-heteroatom bond forming reactions is well established in the context of classical oxidation chemistry [1-11]. For example, oxidations of anilines to azobenzenes, thiols to disulfides, and sulfides to sulfoxides with aryl-A3-iodanes were documented decades ago [1-5]. During the last ten years, particular attention has also been given to oxidative transformations of compounds derived from heavier elements, including the interception of reaction intermediates or initially formed products with external nucleophiles. A second important development is the utilization of sulfonyliminoiodanes, ArI = NS02R, for heteroatom-nitrogen bond formation, especially for imidations of sulfur, selenium, phosphorus and arsenic com-... 

In summary, recent investigations of reactions of aryl-A3-iodanes,ArIL1L2,with heteroatom substrates, derived from third-row elements and beyond, provide examples of P-O, S-O, Se-O, Se-P, Se-S, Te-O, Bi-O and Sb-0 bond formation. Sulfonylimino(aryl)iodanes, ArI = NS02R, are especially useful as imidation reagents, and have been utilized for the construction of P-N, S-N, Se-N, and As-N bonds. Diaryliodonium salts have been employed indirectly for formation of the Se-Se bond. 

BTIB-oxidations of aromatic ethers can also be directed to C,C-bond formation. Intermodular examples include oxidative heterocouplings of 1,4-dimethoxybenzene with /1-dicarbonyl compounds, presumably via their enol tautomers, to the arylated /1-dicarbonyl derivatives 102... 

Dibenzazonines have been synthesized by three general approaches (A) construction of the azonine ring from an appropriately substituted biphenyl derivative, (B) formation of the aryl-aryl bond, and (C) by rearrangement of various types of alkaloids. 

Biphenyl bond formation has been achieved in the diiodobiaryl derivative 41 by an intramolecular aryl halide coupling reaction promoted by tetrakis(tri-phenylphosphine) nickel. This short and efficient route gave the dibenzazonine 42 in good yield (42) (Scheme 9). In a similar way, tetrasubstituted derivative 43 was successfully coupled with the more easily prepared tris(triphenylphos-phine)nickel, giving 44 in 62% yield. Subsequent debenzylation led to the most efficient synthesis of dibenzazonine 35a reported to date (43). 

Horseradish peroxidase (HRP) has also been used in an enzymatic process to create aryl-aryl bonds, especially for the synthesis of diiodotyrosine derivatives in a possibly biomimetic transformation [30, 100]. Here again, the regioselectivity of bond formation is an important issue and, depending on both the conditions and the substrate, C-C or C-O-coupling can occur. The effect of substituents ortho to the alcohol group has been studied by Sih and co-... 

Silole rings have been constructed by treating 3,3 -dibromo-2,2 -bithienyl with BuLi and reacting the dilithio derivative so obtained with a dialkyldichlorosilane <2006JA9034>. The aryl-aryl bond formation by electron-transfer oxidation of Lipshutz cuprates has been utilized for the construction of macrocycles involving thiophene rings <2006JOC6110>. 

Nishiyama, and co-workers first reported that the catalyst derived from Pd(OAc)2 and (f-Bu)3P effects the C-N bond formation to produce triarylamines in excellent yield [65]. This system also is useful in the coupling of diarylamines and aryl chlorides. Hartwig and co-workers found this protocol optimal for the preparation of triarylamines. The (f-Bu)3P/Pd-catalyst was sufficiently active such that the coupfing of diarylamines and aryl bromides can be performed at room temperature,Eq. (34) [50]. The (f-Bu)3P/Pd-system has been used to produce new triarylamine-based polymers [ 64 a - d]. 

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