Process for preparing phthalide and naphthalide indicator dyes

A process which comprises the steps of:

• 1. reacting in substantially equimolar proportions in an inert organic liquid solvent at a temperature between about 20.degree.C. and 120.degree.C. in the presence of an acid catalyst selected from toluene-p-sulfonic acid, sulfuric acid, trifluoroacetic acid and trichloroacetic acid, (a) a compound selected from ##SPC33##
• wherein R.sup.1 is selected from hydrogen, alkoxy containing 1 to 3 carbon atoms and alkyl containing 1 to 3 carbon atoms;
• R.sup.2 is selected from hydrogen, hydroxy, carboxy, sulfonamido, sulfamoyl, o-hydroxyphenyl, bis-trifluoromethylcarbinol, methoxy, alkyl containing 1 to 16 carbon atoms;
• R.sup.3 is selected from hydrogen, alkoxy containing 1 to 18 carbon atoms and alkyl containing 1 to 3 carbon atoms;
• R.sup.4 is selected from hydrogen, hydroxy and carboxy;
• R.sup.5 is selected from hydrogen and alkoxy containing 1 to 18 carbon atoms;
• R.sup.6 is selected from hydrogen, phenyl, alkyl containing 1 to 3 carbon atoms, and alkoxy containing 1 to 18 carbon atoms;
• R.sup.7 is selected from hydrogen, phenyl, o-hydroxyphenyl and alkyl containing 1 to 3 carbon atoms and R.sup.8 is selected from hydrogen, cyano, carboxy, halo, trifluoromethyl, sulfonyl and alkoxy containing 1 to 18 carbon atoms with (b) an aldehydic acid selected from phthalaldehydic acid, unsubstituted or substituted in one of the 4- or 7-positions with carboxy and naphthalaldehydic acid, unsubstituted, to form the corresponding adduct having the formula:
• ##SPC34##
• wherein A is a radical selected from p-hydroxyphenyl, p-hydroxynaphthyl, pyrr-2-yl and indol-3-yl corresponding to said (i), (ii) and (iii) and (iv), respectively, and X represents the carbon atoms necessary to complete a ring-closing moiety selected from phthalide, unsubstituted or substituted in the 4- or 7-position with carboxy, and naphthalide, unsubstituted;
• and
• 2. reacting said adduct with a quinone selected from chloranil, o-chloranil and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone in a molar ratio of about 1.1 to 1.5 moles of quinone per 1.0 mole of adduct in an inert organic liquid solvent at a temperature between about 20.degree.C. and 200.degree.C. to form the corresponding oxidation product selected from ##SPC35##
• wherein A and X have the same meaning given above, and ##SPC36##
• wherein A' is selected from ##SPC37##
• wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7 and R.sup.8 and X have the same meaning given above and mixtures of (I) and (II), said (I) being produced under anhydrous conditions and said (II) and said mixtures of (i) and (II) being produced in the presence of moisture.