Syntheses of Graphenes

Classical methods rely on electrocyclization reactions promoted by heat or, especially, by photochemical means, usually followed by an oxidation to deliver the aromatic compound. One of the most prominent routes is also known as the Mallory reaction, first reported in 1964 [84, 85]. Since then it has been further optimized [86] and applied, especially in the synthesis of helicenes [87], but also in a number of syntheses of graphene-type structures. Zhang et al. recently combined the Mallory reaction with a Scholl cyclization to access tetrabenzocoronene 135 (Scheme 33) [88]. A similar approach has been reported for the preparation of hexabenzocoronene [62]. 

The syntheses of graphene nanoribbons and the troublesome problems of keeping the products solution-processable will continue to define challenges for polymer chemistry, but have also suggested another, somewhat unconventional, approach. In a fruitful interaction with the group of Roman Fasel, who are focused on the surface physics and STM detection [213-216] under UHV conditions, we deposited dihalo-substituted, non-planar oligophenylene compounds as precursor... 

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