CS200381B1 - Method of preparing 9-arylxanthenes - Google Patents

Description

(54) A method for preparing 9-arylxantheas

SUMMARY OF THE INVENTION The present invention provides a process for the preparation of 9-arylxaathalas and possibly readily available triarylcarbanes.

- Arylxanthenes are used for the preparation of stable xanthyl salts, useful in organic synthesis for the regioselective and oxidation of cyclic alcohols ·

Arylxanthenes have been prepared by condensation of substituted phenols with substituted benzaldehydes (Downey, B. and Lowy A., J. Am. Chem. Soc. 45, 1060 (1923)), or α-hydroxytriarylcarbinols by treatment with hydrogen chloride (Ornbeng M. and Nishida). D., Amer. Chem. Soc., 45, 190 (1923), possibly from the same starting material by heating above the melting point (Berlitzer H., Monatshefte 36, 191 (1915)) or by refluxing and acetic anhydride (Llbannan H., Sarrollier J · Justus Liebigs Ann · Chem. 509. 38 (1934) · Such a synthesis from o-methoxytrlarylcarblnols by aluminum chloride has been proposed (Kaufmann H., Panslts ».» Ber. 43, 1205 (1910), or 9-chlorxanthene). and feaylmagnesium bromide (Cheeseman

6, V, Je, JeCheu, Soc, 1959, 458). These syntheses did not yield quantitative yields or pure products.

High yields and pure products in the preparation of the 9-arylxanthenes of formula I X

R '(1) /

200 381 wherein R ¹ m R ² is hydrogen, or together represent a -CH-CHCH-GH group - linked in a ring, X is a hydrogen atom or a halogen, can be achieved by the method of treating aa a substituted hydroxylene substituted triarylmethaaol in position 2 of one of the aryl groups of formula 1 'or III

Kde 2 where R, Ra and X have the same meaning as above, in a water-free hydrocarbon solvent in the presence of a hydrogen chloride or hydrogen bromide in the presence of a desiccant, and after removal of the desiccant, excess hydrogen halide and air yellow color and the product isolated. The most preferred method of isolation is the re-filtration of the precipitated ammonium salt, evaporation to dryness and recrystallization, possibly using another method of purification if the product cannot be recycled by co-crystallization (eg repeated shaking or chromatography).

Suitable hydrocarbon solvents are, for example, benzene, toluene, saturated aliphatic and alicyclic hydrocarbons and mixtures thereof.

The choice of a suitable diluent is important. Anhydrous magnesium sulphate has proven to be the best solution, calcium chloride can also be used. Removing * air oxygen before adding * amine (e.g., blowing * reaction solution with nitrogen) suppresses the oxidation reaction, resulting in a byproduct which is difficult to separate from xaathene.

Of tertiary amines, tore amines are best suited for xanthene isolation ·

By evaporable tertiary amine is meant a tore amine which can be removed from the reaction mixture by evaporation after completion of the reaction without appreciable decomposition of the product. Also suitable are tertiary amines NR 6, wherein R 8 are the same or different, unbranched or branched C 1-6 alkyl, with two of the substituents optionally forming up to a 6-membered ring.

Reakoe proceeds, regardless of any permanent * intermediates *, according to the overall scheme ·

wherein RR ¹ , R ² and X are as defined above. The yields are usually above 90% of the theoretical value. The above process for the preparation of the 9-arylxantheas of the present invention is above 90% yield, while the previously reported methods (Cheeseman GWH, J. Chem. Sec. 1959 458) have yields of 20-40% and the products are very impure.

In the following, the invention is illustrated by the following non-limiting examples

Example 1

To a solution of 0.01 mole of diphenyl 1/3-hydroxy-2-naphthyl / methanol in 200 mL of dry benzene was added 6.0 g (0.05 mL) of anhydrous magnesium sulfate. After cooling to 80 ^° C, hydrogen chloride gas / 3 min was suspended with stirring. 250 ml / min / · reaction mixture was stirred her · Ste 5 minutes, the desiccant was filtered _two frit and washed with dry benzene / 2x 20 ml /. The filtrate was ⁹ at 10 C on a rotary evaporator removed the residual HCl. From the flask containing the benzene solution of triarylmethyl chloride, the air was displaced with nitrogen, and after cooling to 8 ° C, triethylamine (1.5 g, 0.015 mol) was added. The resulting yellow substituted ohinone methide solution was allowed to stand at 20-25 ° C until decolorization. The precipitated triethylammonium chloride was filtered off, the filtrate was evaporated to dryness on a rotary evaporator and the residue was crystallized from ether-petroether or benzene-petroleum ether. The crystalline product benzo (g) -9-phenylxanthene, mp 172-173 ^° C, was obtained in a yield of 95% of theory. Anal. Calcd: C, 89.47; H, 5.28; Found: C, 89.63; H, 5.19.

Example 2

The procedure of Example 1 was repeated with the same starting materials. As the tertiary amine used was N-methylpyrrolidine (0.15 mol) · The resulting product mp 172-173 ⁰ C, was obtained benzo (g) - 9 - phenylxanthene about 94% yield.

Example 3

The procedure of Example 1 was repeated with an equivalent amount of bis (4-fluorophenyl) 3-hydroxy-2-naphthylmethanol. As a result, benzene (g) -3-fluoro-9- (4-fluorophenyl) xanthene, m.p. 195-196 ^° C, yield. was 96% of theory.

Analysis: calculated 80.05% 0, 4.11% H, found 80.35% c, 4.11% h.

Example 4

The procedure of Example 1 was repeated using trimethylamine and an equivalent amount of dl (4-bromophenyl) (2-hydroxyphenyl) methanol. The resulting 3-bromo-9- (4-bromophenyl) xanthene had a t r of 187-189. 98% yield ·

Analysis Calculated 54.84% C 2.91% H 55.01% loaded f C 2.73% H _o

Example 5

The procedure of Example 1 was repeated with an equivalent amount of 2- (3-hydroxynaphthyl) bis (4-chlorophenyl) methanol. The resulting beazo (g) - 3 - chloro - 9 - (4-ehlerfeayl) xanthene

Analysis>

calculated found

and was obtained with 92% yield · % c, 3.74% H i % C, 3.50% H. Ø E D M S T OF THE INVENTION

Claims (2)

A process for the preparation of 9-arylxanthenes of formula (I) wherein R, R is hydrogen, or together represent a group - CHeCIEHeCH - linked in a ring, X is hydrogen or halogen, characterized in that the compound is formula II or III (II) (III), η ρ where R, R and X have the same meaning as in Formula I treated in an anhydrous hydrocarbon solvent in the presence of a desiccant with hydrogen chloride or hydrogen bromide, and after removal of the desiccant, excess hydrogen halide and oxygen, NRj formula wherein the substituents R are identical or different, unbranched or branched alkyl C _1, two of these substituents may be taken up to 6 membered ring, the solution was allowed to de disappearance of yellow coloration and the product isolated. 2. Process according to claim 1, characterized in that anhydrous magnesium sulfate is used as drying agent.