Azobenzenes are among the most extensively used molecular switches. Due to the unique tunability of their (photo-)physical characteristics in combination with a high tolerance against photobleaching, azobenzenes can be found in many applications in all fields of photoswitching materials. More recently, ethylene-bridged azobenzenes, the so-called diazocines, have gained attention as they can be switched in both directions using visible light. In contrast to typical azobenzenes, the (Z)-isomer is the thermodynamically favoured form. In order to exploit the photoswitchable properties of azobenzenes and diazocines in greater systems, a tailored synthetic strategy as well as the possibility of modification of these photoswitches are needed. Especially if a high yielding, fast and easy process is of paramount importance, for example for the postfunctionalization of polymers or peptides, the incorporation of the photoswitches can be challenging. Cross-coupling reactions have proven to be a powerful tool for late-stage functionalization of azobenzenes. However, only a few examples of cross-coupling reactions using diazocines with mainly low yields have been reported. Here, we present a wide range of high-yielding Suzuki and Stille cross-coupling reactions for the functionalization of diazocines. By incorporation of further functional groups on the coupling partner, post-modification of the corresponding diazocine is possible.

Suzuki vs. Stille: Functionalization of diazocines by cross-coupling reactions

ACS Spring 2022

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