CS256977B1 - Process for the preparation of 2- (p-terphenyl-4-yl) -4,6-diarylpyridines - Google Patents

Abstract

The method of producing 2-(p-terphenyl-4-yl-)- -4,6-diarylpyridines consists in heating a mixture of substances of the general formula II and III VZ{~7>4-CO-CH2-hF}> Br<-> (ii) . \ '—' /m —CO—CH =CH—(mi, /k where m and k take the values 0, 1 or 2, with at least one of the symbols m or k having the value 2, and ammonium salts of carboxylic or mineral acids in the reaction medium of aprotic polar solvents in the presence of the corresponding carboxylic acid. The pyridine derivatives prepared in this way exhibit pronounced luminescence in the crystalline state and in solutions and can therefore be used in the scintillation technique.

Description

(54) A process for preparing 2- (p-terphenyl-4-yl) -4,6-diarylpyridines

A process for the preparation of 2- (p-terphenyl-4-yl) -4,6-diarylpyridines is to heat a mixture of compounds of formula II and III

VZ {~ 7> 4-CO-CH _2} -hf> Br <-> _(II).

\ '-' / m —CO — CH = CH— (mi, / k where the mac is 0,1 or 2, at least one of m or k being 2, and the ammonium salts of carboxylic or mineral acids in the reaction The pydridine derivatives thus prepared exhibit significant luminescence in both the crystalline state and in the solutions and can therefore be used in scintillation techniques.

The invention relates to a method for producing pellets; The novel 2- (p-terphenyl-4-yl) -4,6-diarylpyridines of the general formula (i)

(I) wherein n is 0, 1 or 2.

Of the similar 2,4,6-substituted pyridines of type I, only the lowest homologues having 2 to 6 phenyl or biphenyl residues have been prepared so far. For example, 2,4,6-triphenylpyridine was prepared by reacting benzaldiacetophenone with ammonium acetate in an autoclave under pressure. It is also known to prepare starting from benzaldehyde and acetone, from benzaldiaceto phenone and acetophenone and also from benzalacetophenone itself. The preparation of 2,4,6-triphenylpyridine by the reaction of phenacylpyridinium bromide or phenacylsoquinolinium boramide and benzalacerophenone in acetic acid in the presence of ammonium acetate has also been described in the literature.

Another method for the preparation of 2,4,6-triphenylpyridine consists in reacting phenacyldimethylsulfonium bromide with benzalcetophenone and ammonium acetate in acetic acid or in converting the corresponding pyrile salts to pyridine by heating with ammonia. Similarly, 2-biphenyl-4,6-diphenylpydridine and 2,6-dibiphenylyl-4-phenylpyridine were prepared.

The preparation of 2,4,6-triaryl-substituted pyridines with a built-in p-terphenyl residue at the 2 or 2,6 position has not been described. Of the analogous pydridine derivatives, only 2,4,6-triphenylpyridine and its derivatives with a methoxy group in the para positions of the phenyl groups are mentioned in the literature in relation to the scintillation technique.

This drawback is overcome by the process for the preparation of 2- (p-terphenyl-4-yl) -4,6-diarylpydidines according to the invention which consists in the mixture of compounds of formulas IX and III

(II) where m is 0,1 or 2 (III) where k is 0,1 or 2, boils when at least one of m or k must have a value of 2, in a ratio of 1: 1.5 in the presence of at least A 10-fold excess of (molar) ammonium acetate in the reaction medium of an aprotic polar solvent such as dimethylformamide or dimethylsulfoxide and acetic acid.

The new pyridine derivatives thus prepared exhibit significant luminescence in both the crystalline state and in the solutions and therefore their possible use in scintillation techniques can be envisaged.

The process for preparing 2- (p-terphenyl-4-yl) -4,6-diarylpyridines according to the invention is described in the following examples.

Example 1

Process for the preparation of 2- (p-terphenyl-4-yl) -6- (biphenyl-4-yl) -4-phenylpyridine

0.4 g of 4-cinnamoyl-p-terphenyl (1.1 x 10 mol) and 0.6 g of phenylphenacylpydridine bromide .1.7.10 ** 3 mol were heated to boiling temperature in the presence of 3 g of ammonium acetate. 200 [deg.] C. in 20 ml of a 1: 1 mixture of acetic acid and dimethylformamide for 24 hours. After cooling, the reaction mixture was poured into 200 ml of water and the precipitate was filtered off with suction. The solid obtained was dissolved in a small amount of chloroform and column chromatography was performed on 30 g of silica using a 1: 9 mixture of benzene-carbon tetrachloride.

Fractions containing the desired material were combined and evaporated. 0.3 g of the desired product was obtained in a yield of 60%. Crystallization from chloroform-methanol gave a white crystalline solid having a melting point of 259-261 ° C.

Example 2

A process for preparing 2- (p-terphenyl-4-yl) -6- (biphenyl) -4-phenylpyridine

0.4 g of 4-cinnamoylbiphenyl (1.4 x 10 mol) and 0.91 g of biphenylylphenacylpyridinium bromide 3 (2.11 x 10 mol) were heated to boiling at 200 ° C in the presence of 1.5 g of ammonium acetate. for 24 hours in 1: 1 dimethylformamide-acetic acid. Product separation was carried out as in Example 1. 0.454 g of product was obtained, which represents a yield of 60%. Crystallization from pyridine gave a melting point of 259.5-261.5 ° C.

Example 3

A process for the preparation of 2- (p-terphenyl-4-yl) -4-6-diphenylpyridine

0.4 g of 4-cinnamoyl-p-terphenyl (1.1 x 10 mol) and 0.47 g of phenacylpyridinium bromide (1.7 x 10 mol) and 3 g of ammonium acetate were treated in the same manner as in Example 1.

0.51 g of the desired product is obtained in a yield of 65% with a melting point of 225-226 ° C.

Example 4

A process for the preparation of 2- (p-terphenyl-4-yl) -4,6-diphenylpyridine

4.3 g of biphenylylphenacylpyridinium bromide (1.0 x 10 mol) and 1.17 g of cinnamoylbenzene-2 (8 x 10 mol) and 10 g of ammonium acetate and 120 ml of 1: 1 acetic acid and dimethylformamide were heated to boiling at 200 ° C. ° C for 75 hours. Further procedure was similar to Example 1. 1.43 g of the desired product were obtained in a yield of 40% at a melting point of 225-226 ° C.

Example 5

A process for the preparation of 2,6-di- (p-terphenyl-4-yl) -4-phenylpyridine

-3 -3

0.4 g of 4-cinnamoyl-p-terphenyl (1.1 x 10 mol) and 0.73 g (1.7 x 10 mol) of biphenylylphenacyl pyridinium bromide and 0.3 g of ammonium acetate were treated in the same manner as in Example 1 0.057 g of the desired product was obtained in a yield of 8.5% with a melting point above 310 ° C.

Claims (1)

OBJECT OF THE INVENTION A process for the preparation of 2- (p-terphenyl-4-yl) -4,6-diarylpyridines of formula I (I) wherein n is 0, 1 or 2, characterized in that a mixture of compounds of formulas II and III is heated to boiling. M ^BrW (II) wherein m is 0, 1 or 2 and MO = co-ch = ch (III) wherein k is 0,1 or 2, wherein at least one of m or k must have a value of 2, in a ratio of 1: 1.5 in the presence of at least a 10-fold molar excess of molar ammonium acetate; in a reaction medium of an aprotic polar solvent such as dimethylformamide or dimethylsulfoxide and acetic acid.