Nanostructured forms of graphene with well-defined structures, including graphene nanoribbons (GNRs) and graphene quantum dots, have attracted interest as high performance semiconductors and luminescent probes. Top-down approaches, including patterning graphene or unzipping carbon nanotubes (CNTs), have provided access to GNRs and allowed their electronic properties to be measured, but these methods do not provide atomically precise control over the GNR width and edge structure. Bottom-up approaches, in which GNRs are synthesized from specific molecular precursors, promise to provide such control but have so far not produced sufficiently long, dispersed ribbons deposited on insulating substrates. We developed a solution based bottom-up synthesis of GNRs, which relies on a benzannulation reaction at each carbon-carbon triple bond of poly(phenylene ethynylene)s (PPEs) followed by oxidative dehydrogenation for graphitization. PPEs are attractive GNR precursors because their polymerization is well established, tolerates a broad range of functional groups, and provides high molecular weight materials. The can be applied to small molecules which are intriguing and previously unavailable polycyclic aromatic hydrocarbons (PAHs). Resulting contorted and highly dispersible PAHs exhibit strongly red shifted absorption spectra and their bandgaps can be tuned by extended conjugation. Benzannulation reaction used in the synthesis of carbon nanostructures is highly regioselective. The main determining factor in regioselectivity is the electronics of the dienophile. This knowledge will allow rational design of regioseletive synthesis of carbon nanostructures.