The synthesis of a series of 2‐thioethers of 1,4‐dihydroxyanthraquinone by various preparative routes is described. The colour, dyeing and fastness properties on synthetic‐polymer fibres of these dyes is discussed in terms of the nature of the substituent in the thiol group. 2‐(2‐aminophenylthio)‐l, 4‐dihydroxyanthraquinone, which gave the new heterocycle 6,13‐dihydroxyanthra‐[2,3‐b]benzo[d]thiophen‐7,12‐dione on Pschorr intramoleadar cyclization, was observed to undergo cyclization, during both its synthesis and its application to polyester fibres, to the blue coloured 7‐hydroxy‐14H‐mphtho[2,3