An Iterative Approach to Unsaturated and Partially Saturated [7]Helicenes
Tyll Freese1, Peter G Jones2, Daniel B Werz1
1Technische Universität Braunschweig, Institute of Organic Chemistry, 38106 Braunschweig, Germany.
Abstract:
We report a simple, iterative strategy for the synthesis of [7]helicenes starting from substituted 1,4-xylene building blocks. In the first step, we take advantage of the deprotonatable methyl groups to achieve ethano-bridged dimers. These are oxidatively coupled (without using metal-containing catalysts or light) using a hypervalent iodine reagent. Both steps are repeated to obtain the respective σ/π-helicenes. The degree of saturation can be controlled thermally during the oxidative coupling.
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