AT- aryl

The first -PDA antiozonants were low molecular weight -diaLkyl-/)-PDAs which caused skin irritations. Current higher molecular weight -dialkyl or A/-alkyl-AT-aryl derivatives are not primary skin irritants. A notable exception is A/-(I-methylethyl)-A7-phenyl-/)-PDA, which causes dermatitis. However, since some individuals are more sensitive than others, antiozonants should always be handled with care (46). When skin contact does occur, the affected area should be washed with mild soap and water. In case of eye contact, flush weU with water. Inhalation of mbber chemicals should be avoided, and respiratory equipment should be used in dusty areas. 

Azetidines, 7, 237-284, 238-246 addition compounds with trimethylboron, 7, 240 AT-alkylation, 7, 240 applications, 7, 246 AT-arylation, 7, 240 azetidin-2-ones from, 7, 263 bicyclic... 

Grubbs reported the synthesis of several N, N -aryl substituted imidazolinium salts 35 from chiral Ar,AT -aryl diamines obtained by palladium-catalyzed amination of the appropriate aryl bromide with (li, 2i )-diaminocyclohexane... 

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). 

Even more attractive is the prospect of preparing phenazines in a single synthetic operation by sequential inter-Zintramolecular AT-arylation. This would require the transformation of either two o-haloanilines 122 and 135 or of an o-phenylenediamine 82 with an o-dihalobenzene 136. Until recently, not even a single example could be found for this one-step synthesis of heterocycles via double Pd-catalyzed AT-arylation. Numerous experiments conducted in a variety of different combinations of various Pd catalysts, bases, and phosphine ligands in our laboratory failed to realize this novel synthetic principle. 

Some breakthrough was finally achieved by using Pd2(dba)3 as the Pd complex, tris(tert-butyl)phosphine as the ligand, and sodium ferf-butoxide as the base [90]. This combination of reagents proved to bring about the synthesis of unsubstituted phenazine (137) by reaction of two molecules of 2-bromoaniline (131). Remarkably, no reaction takes place under the conditions of the 133 117 transformation. Currently the scope and limitations of this new sequential inter-Zintramolecular AT-arylation for the synthesis of AT-heterocycles... 

Attention to catalyst preparation and reaction conditions is of crucial importance for the success of an Ir-catalyzed allylic substitution, because many ligands are altered by C—H activation at aryl (see above) or CH3 groups. For most reactions, tetrahydrofuran (THF) is the preferred solvent it is important that dry THF (<35gg H20mr THF, Karl Fischer titration) is used for catalyst preparation because this step is very sensitive to water. The following procedures have been appHed. 

The Ar-(3-cyclopropyl-2,4-pyrimidyl)- 96a and hT-(3-cydopropyl-2,4,6-tri-azinyl)-AT-aryl sulfonyl ureas 96b (R = halo-, amino-, alkoxyalkyl and cycloalkyl X = CH, N) are useful as plant growth regulators and herbicides. At 500 g per ha the cyclopropyltriazine derivative 96 b (R = OMe, Ar = 2-carbomethoxy-phenyl) killed Abutilon species and Sivapis alba or prevented germination without affecting wheat, Eq. (37) [128]. 

The oxidation of AT-substituted 5//-dibenz[6,/] azepines with MCPBA is complex and depends upon the nature of the N-substituent. AT-Acyl derivatives do not form the N-oxide but suffer epoxidation of the 10,11-bond. AT-Aryl derivatives undergo hydroxylation of the phenyl ring, whereas N-alkyl congeners, with the exception of the AT-methyl compound, yield mixtures of diphenylamines and acridones. The N-oxide is obtained from the A/-methyl derivative along with ring-opened and ring-contracted products (81CPB1221). 

IV-Alkyl substituted ureas usually eliminate the IV-substituted amine (80JHC235), but IV-arylthioureas may give ring AT-aryl derivatives (66IJC447). 

Naphthalene endoperoxides have been synthesized with methyl groups located at the 1,4-, 1,8-, 1,2,4-, 1,4,5-, 1,2,3,4-positions, and 1,2,3,4,5,6,7,8-positions in good yield after recrystallization of 58%, 88%, 93%, 54%, 83%, and 69%, respectively [48, 49]. The C—O bond formation preferably takes place at aryl sites bonded by the methyl groups. The stabilities of the endoperoxides were greater with increased numbers of methyl groups on naphthalene [at 25 °C in CDC13, compare... 

Furthermore, Pd-catalyzed aminations can be sequentially coupled with alkene insertion and amination. Wolfe and Lira [102] have established a transformation involving two different sequential metal-catalyzed reactions that lead to AT-aryl-2-benzylindolines 125 in moderate to excellent yields upon formation of two C - N bonds and one C - C bond in a one-pot process (Scheme 45). Interestingly, the selective installation of two different aryl groups in this sequence can be accomplished by in situ modification of the Pd catalyst system Pd-126 upon addition of the chelating ligand dpephos prior to addition of the second aryl bromide (Scheme 46). The selectively substituted indoline derivatives 127 were isolated in good to excellent yields. 

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