The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 05, 1992
Filed:
Dec. 20, 1990
Hiroaki Harada, Yao, JP;
Yasuhisa Iwasaki, Yao, JP;
Yamamoto Chemicals, Inc., Osaka, JP;
Abstract
A method of producing a high melting point 3-dibutyl amino-6-methyl-7-anilinofluoran characterized by peaks at diffraction angle (2 .theta.) of 6.9.degree., 11.0.degree., 18.5.degree. and 18.9.degree. in X-ray diffractiometry using Cu-K .alpha. ray and having a melting point in the range of 179.degree.-186.degree. C., which comprises: condensing 2-(4-dibutylamino-2-hydroxy-benzoyl) benzoic acid with 4-methoxy-2-methyldiphenylamine in the presence of concentrated sulfuric acid to provide a phthalide at a temperature in the range of 0.degree.-50.degree. C., neutralizing the phthalide, and then subjecting the phthalide to ring closure reaction using an alkali in an amount of 0.5-15 mols per mol of the compound used in smaller amounts of 2-(4-dibutylamino-2-hydroxy-benzoyl) benzoic acid and 4-methoxy-2-methyldiphenylamine at a temperature of not less than 50.degree. C. in the presence or absence of an organic solvent.