Patent ID: 7691197

Claim:
A method of preparing a yellow pigment comprising the steps of: a) combining, in any order, i) a reagent having the formula A n Ar—NH—CH(COX)—CO—COY (I), ii) an aniline compound having the formula B n Ar—NH 2 (II), and iii) a solvent to form a mixture comprising an asymmetric derivative having the formula A n Ar—NH(COX′)C═C(COY′)NH—ArB n (III); and b) converting the mixture to the yellow pigment, wherein Ar is an aromatic group; n is 0-4; A, which can be the same or different when n is greater than 1, is a substituent on the aromatic group; B, which can be the same or different when n is greater than 1, is a substitutent on the aromatic group wherein A n Ar and B n Ar are different; X, X′, Y, and Y′, which can be the same or different, represent —OH, —O − M + , —OR, —NHR, or —NR 2 , wherein M + is a metal ion and R is independently a C1-C6 alkyl group; and wherein the yellow pigment comprises an asymmetric quinolonoquinolone in an amount greater than 50% by weight of the yellow pigment.