Uncatalyzed cross-coupling reactions

Displacement at Carbon Uncatalyzed Cross-coupling Reactions... 

Uncatalyzed Cross-Coupling Reactions of Organozinc Reagents I 291... 

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. 

Another gain in diversity is achieved by the combination of these cross couplings with uncatalyzed reactions. Because of their oligounsaturated character, the coupling products are obviously well suited for subsequent peri-cyclic reactions leading to additional cyclizations. These atom-efficient processes are especially attractive since they typically proceed with high chemo-, regio- and stereoselectivity [18]. This review is intended to cover Heck reactions and related palladium-catalyzed processes followed by Diels-Alder reactions, 1,3-dipolar cycloadditions or 6 -electrocyclizations. 

Halodendralenes are valuable substrates for dendralene to dendralene transformations that preserve or extend the dendralene framework. They are intermediates in the synthesis of [7]- and [8]dendralene (Scheme 1.26) [23], as are their nucleophilic relatives, pinacolatoboryldendralenes, in the synthesis of substituted [4]-, [5]-, and [6] dendraienes [25, 27]. (Pseudo)halodendralenes have also been used in Stille [209] and Sonagashira cross-couplings [178, 210]. Dendralene dimers can be obtained via homocoupling of halodendralenes [211]. Dendralene frameworks can also be extended by uncatalyzed metathesis reactions on alkyne-containing dendraienes, and olefination reactions on carbonyl-containing ones [1, 211-214], each of which has been discussed. 

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