Darstellung von poly‐methylphenylenen nach grignard. Über methylsubstituierte polyphenylene. IV. Mitt.

Abstract

Die Einwirkung von 4,4'-Dijod-3,3'-dimethyldiphenyl bzw. von 2.5-Dibromtoluol auf Magnesium fiihrt zu rnethylsubstituierten Polyphenylenen. Die Reaktionsbedingungen der Grignardreaktionen wurden in mehrfacher Hinsicht variiert. Man erhiilt keine linearen Makromolekiile, wie dies friiher auch bei der Ullmannreaktion mit Kupferpulver festgeetellt wurde. Die Grignardreaktian eignet sich trot2 der milden Reaktionsbedingungen schlechter fiir die Synthesc linearer Polyphenylene als die Ullrnannreaktion. SUMMARY:The corresponding methyl-substituted polyphonylenes of 4,4'-diiodo-3,3'-dimethyldiphenyl or 2,5-dibromotoluene are obtained by treatment with magnesium. The con-

Dimensional Evolution of Polyphenylenes: Expanding in All Directions

“…Soon thereafter various groups worked to develop a nickel-catalyzed aryl–aryl coupling mechanism to form polyphenylenes, which is currently known as Kumada reaction conditions (Figure , blue mechanism). In this case a Grignard reagent was used to activate halide-functionalized benzene rings, and utilizing different nickel-based catalysts , polyphenylenes were synthesized with moderate molecular weights and lower polydispersities than those made by the Ullmann method. The combination of milder reaction conditions and better control over the resulting polymer structure, as compared to Ullmann conditions, encouraged further research into alternative transition metal coupling mechanisms. − Yet the inability to achieve high molecular weights and the need for Grignard reagents during Kumada-based reactions led to subsequent improvements in nickel-catalyzed techniques.…”