Process for preparing squarylium compounds

Claim 1

A process for preparing a squarylium compound represented by formula (III): ##STR12## wherein R 1 , R 2 , R5, and R6 each represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted phenyl group, or a substituted or unsubstituted benzyl group; and R 3 , R 4 , R 7 , and R8 each represents a hydrogen atom, a substituted or unsubstituted alkyl group, a halogen atom, a hydroxyl group, a carboxyl group, a carbonamido group substituted with a substituted or unsubstituted alkyl group or a substituted or unsubstituted phenyl group, or a sulfonamido group substituted with a substituted or unsubstituted alkyl group or a substituted or unsubstituted phenyl group, in which process comprises dropwise adding a solution of an arylhydroxycyclobutenedione salt represented by formula (I-1): ##STR13## wherein R 1 , R 2 , R 3 , and R 4 are as defined above; and M + represents an alkali metal ion, a tetraalkylammonium ion, a trialkylammonium ion, a substituted or unsubstituted pyridinium ion, or a substituted or unsubstituted quinolinium ion, or a hydroxycyclobutendione derivative represented by formula (I-2): ##STR14## wherein R 1 , R 2 , R 3 , R 4 are as defined above, in a solvent, to an alcohol solution of an aniline derivative represented by formula (II): ##STR15## wherein R 5 , R 6 , R 7 , and R 8 are as defined above, in an alcohol solvent, to effect reaction.