CS253807B1 - Process for preparing 2-aryl-6-amino-2,3-dihydro-1,2,4-benzotriazin-3-ones - Google Patents

Abstract

Process for preparing 2-aryl-6-amino-2,3-dihydro-1 Of 2,4-benzotriazin-3-one in general of formula II wherein R is hydrogen, methyl, methoxy or chlorine, rests in that 4-aminoazobenzen-2-yl-carbamate is present of the formula I wherein R is as defined above, cyclized by boiling in acid or by boiling in a solvent with a boiling point above 200 ° C, or by heating to the temperature at which it occurs the solidification of the melt to form a 2-aryl-6-amino- -2,3-dihydro-1,2,4-benzotriazin-3-one in general of formula II wherein R is as defined above. The compounds are dyeing to wool, silk and leather.

Description

The invention relates to the preparation of 2-aryl-6-amino-2,3-dihydro-1,2,4-benzotriazin-3-ones of formula II wherein R is hydrogen, methyl, methoxy or chloro.

The heterocyclic dyes of formula II are prepared by boiling 2,4-bis-ethoxycarbonylamino-azobenzenes in a strongly acidic medium (J. Slouka, V. Bekarek: Coll. Czeoh. Chem. Commun. 45, 137 (1980)).

The preparation of 2-aryl-6-amino-2,3-dihydro-1,2,4-benzotriazin-3-ones of the general Formula IX, wherein R is as defined above, is characterized by cyclization of 4-aminoazobenzene 2-yl ethyl carbamates of the formula I, wherein R is as defined above. The cyclization may be carried out by boiling in an acidic medium, boiling in a solvent boiling above 220 ° C, or by heating compounds of formula I wherein R is as defined above to melt solidification to form a compound of formula II wherein R is as defined above.

An advantage of the process according to the invention is the easy availability of the raw material of the formula I and its cyclization under milder conditions compared to the other methods of its preparation. The compounds of formula (II) may be used to color wool, silk, leather and the like.

The preparation of compounds of formula II is illustrated by the following examples.

He did

A mixture of ethyl ethyl 4-aminoazobenzen-2-ylcarbamate (285 mg, 1.00 mmol), water (25 ml) and 37% HCl (8 ml) was refluxed for 3 h and then evaporated in vacuo. The residue was stirred with 6 ml of 5% NH 4 and the crystalline compound of formula II, where R = H was aspirated after several hours, washed with water and dried. Yield 215 mg (89.7%).

Example 2

A mixture of 285 mg (1.00 mmol) of the azo compound of formula I wherein R = H and 10 mL of diphenyl oxide was 30 min. cooked under reflux. It was then stripped of most of the solvent in vacuo and diluted with hexane. The crystalline material was aspirated, washed with hexane and dried. Yield: 210 mg (88.2%).

Example 3

The azo compound of formula (I) wherein R = H (285 mg = 1.00 mmol) was heated above the melting point and the melt temperature was gradually raised up to the point where crystallization of the corresponding derivative II (250 ° C) began and maintained at this temperature. until most of the melt crystallized. The temperature was then raised to 260-270 ° C and the crystalline substance was cooled. Yield: 210 mg (88.23%).

After recrystallization from ethanol (using a small amount of activated carbon), the compounds prepared by any of the above procedures are identical in all properties, including IR spectrum, to 2-phenyl-6-amino-2,3-dihydro-1,2,4-benzotriazine-3. -one prepared previously from 2,4-bis-ethoxycarbonylamino-azobenzene (J. Slouka, V. Bekarek: Coll. Czech. Commun. 45, 1379 (1980)).

For C 4,2 jH, qNNO (238.24) calculated: 65.53% C, 4.23% H, 23.52% N found: 65.25% t, 4.31% H, 23.38% N

Electron spectrum of 2x10 µM ethanolic solution II, λ _max (log log): 235 nm (4.49), 267 nm (4.39), 386 nm (4.25).

Compounds of formula II wherein R = CH ₃ , CH ₃ O and Cl were prepared analogously and in corresponding yields. .

Claims (4)

A process for the preparation of 2-aryl-6-amino-2,3-dihydro-1,2,4-benzotriazin-3-ones of the general formula II, wherein R is hydrogen, methyl, methoxy or chloro, characterized in that cyclization of ethyl 4-aminoazobenzen-2-yl-carbamates of formula I wherein R is as defined above. 2. The process of claim 1 wherein the compound of formula I wherein R is as defined above is cyclized by boiling under acidic conditions. 3. A process according to claim 1 wherein the compound of formula I wherein R is as defined above is cyclized by boiling in a solvent boiling above 220 ° C. 4. The process of claim 1 wherein the compound of formula I wherein R is as defined above is cyclized by heating to a temperature at which the melt solidifies.