Isoindoline constitutions

Figure 14—4 shows the structural formulae of these six isoindoline constitutions listed in the Colour Index. The pigments cover the range from greenish yellow (P.Y. 185), to reddish yellow (P.Y. 139), to orange (P.O. 66 and 69), red (P.R. 260) and brown (P.Br. 38). 

Isoindolines comprise a group of well-characterized and easily synthesized substances, and being at the next stable reduction state below that of isoindoles, they constitute suitable precursors for synthesis of the latter. In principle, either oxidation or elimination from isoindolines should lead to isoindoles however, in view of the susceptibility of isoindoles to further oxidation, elimination has been preferred, and in all cases reported the leaving group has been placed on nitrogen rather than carbon. 

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