Construction of polycyclic heteroaromatics via metal-catalysed intramolecular X-CH activation

π-Conjugated heteroaromatic systems are known for their unique optical and electronic properties and are important for a wide range of semiconducting applications. Metal-catalysed C-H activation has emerged as a key strategy for developing a facile and economic route for the synthesis of a variety of novel π-conjugated heteroaromatics, which otherwise involves multistep synthesis through conventional methods. In this review, we summarise the synthesis, properties and applications of several heteroaromatics, such as N-heteroheptacenes, benzo[de]thioacenes, π-extended thienoacenes, metallocene siloles, spirosilabifluorene, benzo[b]silole-fused 9,9'-spirobi[fluorene], sila[6]helicenes, tetragermatetrathia[8]circulene, trisilasumanene, trigermasumanene, and tetrasilatetrathia[8]circulenes, which have been developed using the X-CH activation strategy.