GB1156800A - Optical Brighteners and process for preparing them - Google Patents

Abstract

1,156,800. Benzoxazole derivatives. FARBWERKE HOECHST A.G. 28 Dec., 1966 [27 Dec., 1965 (2)], No. 57900/66. Heading C2C. [Also in Division D1] Compounds of the formula wherein Y represents a carboxylic acid group, an esterified carboxylic acid group, a carboxylic acid amide group, a carboxylic acid hydrazide group or a nitrile group, and R 1 and R 2 each represent a hydrogen atom, an alkyl group containing up to 4 carbon atoms or R 1 and R 2 in adjacent positions together form a saturated carbocyclic nucleus condensed on to the benzene ring, may be obtained (A) by reacting an oaminophenol of the formula with an acid chloride of a 4-carbalkoxy-naphthoic acid-(1) or of 4-cyanonaphthoic acid-(1) of the formula wherein X represents a -CN or -COOR group, where R is an alkyl group containing up to 4 carbon atoms, heating the N-acyl compound of the formula so obtained, suitably under an atmosphere of an inert gas, in a high boiling solvent, preferably at a temperature above 200‹ C. and optionally in the presence of a catalyst, and optionally converting the 4-[benzoxazolyl-(2<SP>1</SP>)]- naphthoic acid-(1) ester or nitrile into other 4 - [benzoxazolyl - (2<SP>1</SP>)] - naphthoic acid - (1) - esters, -amides or -hydrazides, or (B) by condensing 1 mole of the dichloride of naphthalenedicarboxylic acid-(1,4) with 1 mole of the oaminophenol of the above Formula II in the presence of an acid-binding agent to obtain the N-acyl compound of the formula which, after saponification of the acid chloride radical by heating in an atmosphere of an inert gas in a high boiling solvent to an internal temperature of over 200‹ C., optionally in the presence of zinc chloride, may be converted into the corresponding 4-(benzoxazolyl-(2<SP>1</SP>)]- naphthoic acid-(1) from which other derivatives of the above Formula I may be obtained by conventional methods. The amide derivatives of Formula I may be obtained by the reaction of ammonia or the appropriate amine with the corresponding 4 - [benzoxazolyl - (2<SP>1</SP>)] - naphthoic acid-(1) chloride and said amide derivatives may then be dehydrated in the presence of a dehydrating agent to yield the corresponding nitriles. The acid hydrazides of Formula I may be obtained by reacting hydrazine or a substituted hydrazine with the appropriate 4-[benzoxazolyl-(2<SP>1</SP>)]-naphthoic acid-(1) methyl ester or acid chloride. The products are stated to be useful as U.V. absorbers and optical brightening agents.