Arenes polyhalogenated

The dehalogenation of several types of polyhalogenated arenes has been studied by Hofs group [61-67]. Brominated thiophenes and bithiophenes were re-... 

Tab. 37 Nitro-arene aus Arenen durch Nitrierung mil 3-Nitro-6-oxo-polyhalogen-l, 4-cyclohexadienen...

Polyhalogenated arenes can function as diaryne equivalents via the tandem sequence illustrated in Scheme lO.90-91 The predominant meta addition to aryne (59) can be ascribed to steric hindrance, while in addition to (58) both steric and electronic effects favor the observed regioselectivity. 

Multiple arylations of polybromobenzenes have been conducted to generate electron-rich arylamines. Tribromotriphenylamine and 1,3,5-tribromobenzene all react cleanly with A-aryl piperazines using either P(o-tolyl)3 or BINAP-ligated catalysts to form hexamine products [107]. Reactions of other polyhalogenated arenes have also been reported [108]. Competition between aryl bromides and iodides or aryl bromides and chlorides has been investigated for the formation of aryl ethers [109], and presumably similar selectivity is observed for the amination. In this case bro-mo, chloroarenes reacted preferentially at the aryl bromide position. This selectivity results from the faster oxidative addition of aryl bromides and is a common selectivity observed in cross-coupling. Sowa showed complete selectivity for amination of the aryl chloro, bromo, or iodo over aryl-fluoro linkages [110]. This chemistry produces fluoroanilines, whereas the uncatalyzed chemistry typically leads to substitution for fluoride. 

Multiple arylations of polybromobenzenes were also conducted to generate electron-rich arylamines. Tribromotriphenylamine and 1,3,5-tribromobenzene all react cleanly with iV-aryl piperazines using either P(o-tolyl)3 or BINAP-ligated catalysts to form hexamine products [107]. Reactions of other polyhalogenated arenes have also been reported [108]. 

The exchange reactions of polyhalogenated arenes have been investigated by Tam-... 

In the absence of arene molecules, (CF3C02)2Ni reacts with polyhalogenated aryllithium (LiAr) reagents to form [Ar2Ni] polymers . Treatment of these reaction mixtures with arenes can retard polymer formation and produce (> -arene)Ni(Ar)2 complexes . Analogous complexes of Co(II) can be prepared similarly . 

Arene.. dioxygenases catalyze reactions other than dihydroxylation of aromatics. For example, toluene dioxygenase catalyzes monooxygenation of indene and indan to 1-indenol and 1-indanol, respectively [382], oxidation of polyhalogenated compounds such as trichloroethylene [eq. (24)] [363, 388-390], and stereoselective sulfoxidation of sulfides [391, 392]. 

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