Modular Two-Step Access to p-Extended Naphthyridine Systems - Potent Building Blocks for Organic Electronics.
Efficient synthetic approaches of incorporation of nitrogen into polyaromatic hydrocarbons (PAHs) in different patterns as stabilising moiety for p-extended systems and modification tool for optoelectronic properties remains a challenge until today. In this work we developed a new versatile pathway to napthyridine-based PAHs as non-symmetric and regioisomeric pendant to pyrazine-based PAHs. A combination of a gold-catalysed synthesis of 2-aminoquinolines and the development of an in situ desulfonation and condensation of these precursors are the key steps of the protocol. The shape and type of attached functional groups of the PAHs can be designed in a late stage of the overall synthetic procedure by the chosen anthranile and backbone of the ynamide introduced in the gold-catalysed step. Single crystal X-ray diffraction and the investigation of electronic properties of the compounds show the influence of the attached substituents. All naphthyridine based PAHs show halochromic behaviour implying their use as highly sensitive proton sensor in non-protic solvents.