indanthronen.

1920 F. A. Mason tr. G. von Georgievics Text-bk. Dye Chem. (ed. 2) 449 Indanthrene (or more correctly Indanthrone, which expresses the quinoid character of the compound, whereas the name generally used would correspond to an oxygen-free compound) is a dianthraquinone-dihydroazine.

1921 E. de B. Barnett Anthracene & Anthraquinone xvi. 343 By far the most important method of obtaining the indanthrones is by fusing the β-aminoanthraquinones with caustic alkali.

1921 E. de B. Barnett Anthracene & Anthraquinone xvi. 342 The first cyclic azine of the anthraquinone series to be prepared was trans. bisang.-anthraquinonedihydro azine. This was placed on the market under the name Indanthrene Blue, and the name ‘indanthrene’ has come into general use in the literature. The word ‘indanthrene’, however, is a registered trade name (B.A.S.F.) and is applied to many vat dyes which are not azines. Indanthrene Blue is an anthraquinone derivative and ketonic in structure, and in order to denote its ketonic nature the name should terminate in -one. In the following pages, therefore, the word ‘indanthrone’ is used to denote the ketonic hydroazine, indanthrene (without a capital) being used for the parent, oxygen free hydroazine (trans. bisang.-dihydroanthrazine). Where ‘Indanthrene’ is used as a registered trade name it is spelt with a capital.

1954 I. L. Finar Org. Chem. (ed. 2) I. xxxi. 689 Indanthrone (Indanthrene Blue R; Bohn, 1901) is prepared by fusing 2-amino-anthraquinone with potassium hydroxide in the presence of potassium chlorate or nitrate at 250°.

1959 Jrnl. Amer. Chem. Soc. 81 3762/2 Strong amide resonance contributes greatly to the resonance hybrid of the indanthrones.