Triphendioxazine compounds

A process for preparing a triphendioxazine compound of formula I

• in which rings labeled A having positions 1,2-, 2,3- or 3,4- and 8,9-, 9,10- or 10,11-, carry a single chain linkage linking such positions, the single chain linkage having a formula selected from the group consisting of —NR5—(CO)m—NH—, —CR5═CH—CO—NH, —CO—CH2—CO—NH, —CO—CH═CR5—NH, —CO—NH—CO—NH, —CO—NH—CR6═N, —CR6═N—CO—NH, —NR5—(CO)m—O and —NH—CR5═N—
• wherein
• R5 is hydrogen, C1-4 alkyl or phenyl;
• R6 is hydrogen, C1-4 alkyl or phenyl;
• and
• m is 1 or 2,
• provided that in a symmetrically disubstituted compound the definitions hydrogen, C1-2alkyl or unsubstituted phenyl are excluded, the process comprising reacting two moles of a compound of formula IV
• in which ring A carries in two corresponding positions the single chain as defined above, with one mole of 2,3,5,6-tetrachloro-1,4-benzoquinone (chloranil)
• and cyclizing the compound of formula XVII to the compound of the formula I in the presence of manganese dioxide and concentrated sulphuric acid.