SU600138A1 - Method of preparing oxy-derivatives of 2-arylbenzasols - Google Patents

Description

eoci well

11 41: i-

NO,

OSI

) NSO

OSSN

 Pd N0,

-NNO-H VOCH3

V- / HC1

H, CO

n co

7JH,

DOS

/ HBr48 ° / o

Despite a number of advantages (high purity of the final product, incomplete instrumentation), this method is multistage, resulting in a low overall yield (55%), although at all stages the yields are at least 90%. Another equally important drawback is the use of aggressive substances and media (acid chlorides, hydrobromic acid and hydrochloric acid).

The purpose of the invention is the development of a preparative method for the preparation of the hydroxy derivatives of 2-arylbenzazole, which makes it possible to increase the yield of the target product.

This is achieved by the proposed method of obtaining compounds of general formula 1, which consists in the fact that the compound of general formula

where R2 is hydrogen, hydroxy or aminogr shpa

X and Y have the indicated values and Ri is hydrogen or an amino group, is diazotized in 45-55% o-phosphoric acid at a temperature from 0 to + 5 ° C, followed by addition of the resulting mixture to the preheated to phosphoric acid concentrated o-phosphoric acid.

The diazotization reaction is carried out in 45-55% o-phosphoric acid at-5 ° C. The resulting diazo compound as a suspension is added without isolation to the 85% o-phosphoric acid heated to boiling. The decomposition of the diazo compound under these conditions proceeds very easily, so that its addition requires no more than 1–2 hours. The reaction progress is monitored by the disappearance of the azo-coupling reaction of the sample of the reaction solution with an alkaline solution of 3-naphthol. By the end of the reaction, everything goes into solution. The selection of the desired dinoxy derivative is carried out by neutralizing the reaction solution with a 10-20% sodium hydroxide solution while cooling.

The proposed method allows to obtain the desired product in two stages with a total yield of 90-95%, based on the starting diamine.

In addition, in a number of cases, the synthesis of the target product is carried out from a commercially available diamine.

Example 1. 5 (6) -Oxy-2- (p-hydroxyphenyl) benzimidazole.

0.02 mol of 5 (6) -amino-2 - ("- aminophenyl) benzimidazole is dissolved in 100 ml of 50% o-phosphoric acid, the solution is cooled to O-5 ° C and with vigorous stirring a liquid layer is added 0.04 mol of sodium nitrite in the form of a 25% solution before the appearance of its stable excess on starch paper. At the end of the addition of sodium nitrite, the solution is kept at about -5 ° C for 1 hour. At the end of the exposure, the resulting solution is added in small portions to a pre-heated to boiling solution of 85% o-phosphoric acid (100 ml). Each Еo the next portion is injected only after the termination of the azo-coupling of the sample of the reaction mass with the alkaline solution of | 3-naphthol.

After adding the total amount of diazo compound, the reaction mass is kept at boiling for 1-2 h, cooled to room temperature, neutralized with soda solution to pH 7. The precipitated 5 (6) -oxy-2 (-oxyphenyl) -benzimidazole is filtered off, washed with water, and dried.

The output of 90-92%, so pl. 283-285 ° С (from HgO), lit. m.p. 280-285 ° C.

Example 2. 5 (6) -Oxy-2- (2-hydroxyphenyl) benzimidazole.

A solution of the diazo compound in 50% o-phosphoric acid from 0.02 mol of 5 (6) -amino-2- (2-oxyphenyl) -benzimidazole is subjected to decomposition as in example 1.

Output 89-92%, so pl. 246-248 0.

Paydeno,%: N 12.71; 12.54.

CisHioNzOs. Calculated,%: N 12.37.

Rf Q, 9Q (eluent alcohol benzene 10: 1).

voH 3455cM-i (KVG).

Example 3. 2- (2,4-Dioxyphenyl) -benzimidazole.

Prepared similarly to example 1 from 2- (2,4-diaminophenyl) -benzimidazole.

Yield 82-90%; m.p. 269 ° C.

Found,%: C 68.45; H 4.55; 4.93;

Ci3HioN202.

Calculated,%: C 69.03; H 4.43; 0.90 (eluent ethanol-benzene 10: 1). voH 3360cM-i.