Coloured products from thiophene and aromatic 1,2-diketones

Thiophene and phenanthrene-9,10-quinone react in acidic solution to produce the deep blue extended quinone (Z,Z)-2,5-di(9-oxo-9,10-dihydro-10-phenanthrylidene)-2,5-dihydrothiophene the structure of which is confirmed by X-ray crystallography. Other aromatic 1,2-diketones give rise to related products.