UK   scientists have used highly inert fluorine-containing arylgermanes to synthesise biaryl functional groups. Such biaryls are often found in products ranging from anti-fungal agents to optoelectronic devices. 

Alan Spivey and colleagues at Imperial College, London, Syngenta and GlaxoSmithKline have developed a class of arylgermanes which can be photochemically activated and employed in a palladium catalysed cross-coupling reaction yielding biaryls. 'The chemistry is unique in allowing for the tethering of one component of the biaryl to a fluorous-tag which acts as a 'handle' to aid purification whilst being highly inert to chemical manipulations during the elaboration of the structure of this component,' said Spivey. 

This method works for both electron rich and electron poor arylgermanes. However, it does not tolerate sterically hindered ones. Using this methodology, Spivey prepared some agrochemical derivatives of the anti-fungal reagent Boscalid®. The researchers hope that the method will also be applicable to the construction of more extensively conjugated (hetero)aromatic systems will provide the next generation of organic semiconductors as components of 'plastic' electronic and optical devices such as high-mobility field-effect transistors for e-paper (and other flexible displays) and low-cost solar panels. 

In the future, Spivey hopes to adapt the technology to a 96-well plate format and sees the work focussing on the optimisation of the photolytic activation step so as to maximise its compatibility with other chromophores. This will allow for delivery of light via fiber-optic threads, probably from a UV diode source and require parallel fluorous phase purification of intermediates. 'Once the optimal wavelength has been identified, the stage will be set for the rapid synthesis of libraries for high-throughput screening,' said Spivey. 

Kathleen Too