RU2152921C1 - Method of dechlorination of substituted chloroaromatic compounds - Google Patents

Abstract

FIELD: chemical industry. SUBSTANCE: describes is method of dechlorination of substituted chloroaromatic compounds by reacting reducing agent (zinc, magnesium or aluminium and catalytic amounts of complex nickel compounds generated in situ with bi dentan nitrogen-containing ligands 2,2'-bipiridyl or 1,10- phenanthroline in bipolar solvent in presence of proton source at 70-150 C. EFFECT: simplificatio of process, reduced cost price, ecologically pure and increased yields of products. 38 ex, 8 tbl

Description

R¹=R²=R³=R⁴=R⁵=H (1);
R¹=R²=R⁴=⁵=H, R³=CH₃ (2);
R¹=R²=R⁴=R⁵=H, R³= OCH₃ (3);
R¹=R²=R⁴=R⁵ H, R³=C₂H₅ (4);
R²=R³=R⁵=H, R¹=R⁴= CH₃; (5);
R¹=R²=R⁴=R⁵=H; R³=NH₂ (6),
R¹=R²=R³=R⁴=R⁵=F (7);
R¹=R²=R³=R⁴=R⁵=CH₃ (8)
R¹=R²=R⁴=R⁵=HR³=Cl (9);
R¹=R²=R⁴=R⁵= H, R³ =COOH (10);
R¹=R²=R⁴=R⁵=H, R³=COCH₃ (11);
R¹=R³=R⁵=F, R²=R⁴= Cl (12);
R¹=R⁴, R²=R³=R⁵=Cl (13);
R¹=R²=R³=R⁴=R⁵=Cl (14);
R¹=R²=R⁴=R⁵=H, R³= C₆H₄Cl (15);
R¹=R²=R⁴=R⁵=Cl, R³=C₆Cl₅ (16)
R¹=R²=R³=H, R⁴=R⁵= -CH=CH-CH=CH- (17);
R¹=R²=R⁵= H, R⁴+R³= -CH=CH-CH=CH-(18);
R¹=R²=R³=Cl, R⁴+R⁵= -CCl=CCl-CCl=CCl- (19).The invention relates to methods for dechlorination of substituted chloroaromatic compounds of the formula

R ¹ = R ² = R ³ = R ⁴ = R ⁵ = H (1);
R ¹ = R ² = R ⁴ = ⁵ = H, R ³ = CH ₃ (2);
R ¹ = R ² = R ⁴ = R ⁵ = H, R ³ = OCH ₃ (3);
R ¹ = R ² = R ⁴ = R ⁵ H, R ³ = C ₂ H ₅ (4);
R ² = R ³ = R ⁵ = H, R ¹ = R ⁴ = CH ₃ ; (5);
R ¹ = R ² = R ⁴ = R ⁵ = H; R ³ = NH ₂ (6),
R ¹ = R ² = R ³ = R ⁴ = R ⁵ = F (7);
R ¹ = R ² = R ³ = R ⁴ = R ⁵ = CH ₃ (8)
R ¹ = R ² = R ⁴ = R ⁵ = HR ³ = Cl (9);
R ¹ = R ² = R ⁴ = R ⁵ = H, R ³ = COOH (10);
R ¹ = R ² = R ⁴ = R ⁵ = H, R ³ = COCH ₃ (11);
R ¹ = R ³ = R ⁵ = F, R ² = R ⁴ = Cl (12);
R ¹ = R ⁴ , R ² = R ³ = R ⁵ = Cl (13);
R ¹ = R ² = R ³ = R ⁴ = R ⁵ = Cl (14);
R ¹ = R ² = R ⁴ = R ⁵ = H, R ³ = C ₆ H ₄ Cl (15);
R ¹ = R ² = R ⁴ = R ⁵ = Cl, R ³ = C ₆ Cl ₅ (16)
R ¹ = R ² = R ³ = H, R ⁴ = R ⁵ = -CH = CH-CH = CH- (17);
R ¹ = R ² = R ⁵ = H, R ⁴ + R ³ = -CH = CH-CH = CH- (18);
R ¹ = R ² = R ³ = Cl, R ⁴ + R ⁵ = -CCl = CCl-CCl = CCl- (19).

 The method can be used in organic synthesis to remove a chlorine atom from an aromatic ring [J.Chem. Soc., Perkin Trans 1, 1973, p. 2509], to obtain practically significant aromatic compounds [Izv. USSR Academy of Sciences, ser. Chem. , 1963, p. 1524], and as a method of neutralizing toxic polychloroaromatic compounds [J. Org. Chem., 1991, V. 56, p. 6145].

A method is described [Organometallics, 1991, V. 10, p. 1620], which is the reductive dechlorination of substituted chlorobenzenes with hydrogen at 25-80 ^o C in the presence of rhodium complexes under conditions of interfacial catalysis (Analog 1). The reaction is carried out in a mixture of 40% aqueous alkali and toluene at a temperature of 25-80 ^o C for 5-48 hours. Benzyltriethylammonium chloride is used as a phase transfer catalyst (Scheme 1).

R = H (1) - 97%*, CH₃ (о - (20)-7%, м - (21) - 95%, п - (2) - 97%), OCH₃ (22) - 99%, CF₃ (23) - 87%, NH₂ (6)-91%, COCH₃ (11) - 97%, COOH(10)-99%, COOPh (24)-98%.

R = H (1) - 97% *, CH ₃ (о - (20) -7%, m - (21) - 95%, n - (2) - 97%), OCH ₃ (22) - 99% , CF ₃ (23) - 87%, NH ₂ (6) -91%, COCH ₃ (11) - 97%, COOH (10) -99%, COOPh (24) -98%.

 Cy = cyclohexyl.

 * - indicates the yield of dechlorination products (according to GLC).

Scheme 1
The yields of the target products, determined by GLC, are 7-99%. The disadvantages of the method are the use of hydrogen gas and the high cost of the catalyst.

The method [J. Mol. Catal. 1992, v.73, p. 173] dechlorination of substituted chlorobenzenes under the conditions of catalysis with palladium complex compounds using sodium formate or methanol as a reducing agent, the reaction is carried out in an aqueous alkali solution at a temperature of 100 ^o C for 20 h (Analog 2) (Scheme 2).

R = H (1)-90%*, CHO(25)-100%, CN(26)-100%, NO₂(27)-70%, COCH₃(11)-87%, OCH₃(3)-11%, NH₂(6) -15%, CH₃(2)-14%.

R = H (1) -90% *, CHO (25) -100%, CN (26) -100%, NO ₂ (27) -70%, COCH ₃ (11) -87%, OCH ₃ (3) -11%, NH ₂ (6) -15%, CH ₃ (2) -14%.

 dippp = 1,3-bis (diisopropylphosphino) propane.

 * - indicates the yield of dechlorination products (according to GLC).

Scheme 2
The disadvantages of this method are the long reaction time and the high cost of palladium complex compounds.

The closest analogue to the claimed method is the method proposed by I.Colon [J. Org. Chem., 1982, v. 47, p. 2622, US 4400566, 1983], which consists in the fact that dechlorination of aryl halides occurs under the influence of metals (zinc, aluminum, calcium, magnesium) in the presence of in situ generated from nickel salts (II ) and triarylphosphine (usually triphenylphosphine) nickel complexes. The reaction proceeds in a nitrogen atmosphere at 70 ^o C for 1-2 hours. Dimethylformamide is used as a solvent, water is used as a proton source (Scheme 3).

R = H(1)-66%*, OCH₃ (3)-97%, CH₃ (2)-92%, CN (26)-90%, CH₂OH (28)-97%.

R = H (1) -66% *, OCH ₃ (3) -97%, CH ₃ (2) -92%, CN (26) -90%, CH ₂ OH (28) -97%.

 * - indicates the yield of dechlorination products according to GLC.

Scheme 3
The yields of dechlorination products range from 66 to 97%.

The disadvantage of the closest analogue is the use as a catalyst of complex compounds of Nickel with triphenylphosphine, which
- are destroyed by the action of atmospheric oxygen, as a result of which the dechlorination reaction is carried out in an inert atmosphere [J. Org. Chem. 1982, v. 47, p. 2622, US 4,400,466 A, 1983, J. Org. Chem., 1986, v. 51, p. 2627];
- interact with free triphenylphosphine under reducing conditions, which leads to the destruction of triphenylphosphine in the course of the reaction and the formation of cross-products of aryl chlorides and triphenylphosphine [J. Callman and others. Organometallic chemistry of transition metals. M.: Mir, 1989];
- make up 30-70% of the mass of the substrate, which complicates the isolation, purification of the target product and the disposal of toxic reaction waste.

где R¹=R²=R³=R⁴=R⁵=H (1);
R¹=R²=R⁴=R⁵=H, R³=CH₃ (2);
R¹=R²=R⁴=R⁵=H, R³= OCH₃ (3);
R¹=R²=R⁴=R⁵=H, R³=C₂H₅ (4);
R¹=R³=R⁵=H, R¹=R⁴= CH₃ (5);
R¹=R²=R⁴=R⁵=H, R³=NH₂ (6),
R¹=R²=R³=R⁴=R⁵=F (7);
R¹=R²=R³=R⁴=R⁵=CH₃ (8)
R¹=R²=R⁴=R⁵=HR=Cl (9);
R¹=R²=R⁴=R⁵= H, R³ =COOH (10);
R¹=R²=R⁴=R⁵=H, R³=COCH₃ (11);
R¹=R³=R⁵=F, R²=R⁴= Cl (12);
R¹=R⁴=H, R²=R³=R⁵=Cl (13);
R¹=R²=R³=R⁴=R⁵=Cl (14);
R¹=R²=R⁴=R⁵=H, R³= C₆H₄Cl (15);
R¹=R²=R⁴=R⁵=Cl, R³=C₆Cl₅ (16)
R¹=R²=R³=H, R⁴=R⁵= -CH=CH-CH=CH- (17);
R¹=R²=R⁵= H, R⁴+R³= -CH=CH-CH=CH-(18);
R¹=R²=R³=Cl, R⁴+R⁵= -CCl=CCl-CCl=CCl- (19).The objective of the invention is to provide a highly effective, more environmentally friendly method of dechlorination of substituted chloroaromatic compounds of the structural formula

where R ¹ = R ² = R ³ = R ⁴ = R ⁵ = H (1);
R ¹ = R ² = R ⁴ = R ⁵ = H, R ³ = CH ₃ (2);
R ¹ = R ² = R ⁴ = R ⁵ = H, R ³ = OCH ₃ (3);
R ¹ = R ² = R ⁴ = R ⁵ = H, R ³ = C ₂ H ₅ (4);
R ¹ = R ³ = R ⁵ = H, R ¹ = R ⁴ = CH ₃ (5);
R ¹ = R ² = R ⁴ = R ⁵ = H, R ³ = NH ₂ (6),
R ¹ = R ² = R ³ = R ⁴ = R ⁵ = F (7);
R ¹ = R ² = R ³ = R ⁴ = R ⁵ = CH ₃ (8)
R ¹ = R ² = R ⁴ = R ⁵ = HR = Cl (9);
R ¹ = R ² = R ⁴ = R ⁵ = H, R ³ = COOH (10);
R ¹ = R ² = R ⁴ = R ⁵ = H, R ³ = COCH ₃ (11);
R ¹ = R ³ = R ⁵ = F, R ² = R ⁴ = Cl (12);
R ¹ = R ⁴ = H, R ² = R ³ = R ⁵ = Cl (13);
R ¹ = R ² = R ³ = R ⁴ = R ⁵ = Cl (14);
R ¹ = R ² = R ⁴ = R ⁵ = H, R ³ = C ₆ H ₄ Cl (15);
R ¹ = R ² = R ⁴ = R ⁵ = Cl, R ³ = C ₆ Cl ₅ (16)
R ¹ = R ² = R ³ = H, R ⁴ = R ⁵ = -CH = CH-CH = CH- (17);
R ¹ = R ² = R ⁵ = H, R ⁴ + R ³ = -CH = CH-CH = CH- (18);
R ¹ = R ² = R ³ = Cl, R ⁴ + R ⁵ = -CCl = CCl-CCl = CCl- (19).

The problem is solved in that the dechlorination process is carried out using a catalyst - nickel compounds (chloride, bromide, nitrate and sulfate) in the presence of nitrogen-containing bidentant ligands, such as 2,2'-bipyridyl or 1,10-phenanthroline. The reaction is carried out under the action of a reducing agent (zinc, magnesium or aluminum) in the presence of a proton source in bipolar solvents such as dimethylformamide (DMF), dimethylacetamide (DMA), N-methylpyrrolidone-2 (MP), dimethyl sulfoxide (DMSO) and hexamethylphosphoric triamide (GMF) ) at 70-150 ^o C. As a source of protons use water, amine salts (ammonium chloride and triethylamine hydrochloride) and dilute solutions of inorganic (HCl) and organic (HCOOH and CH ₃ COOH) acids.

 The reducing agent is taken in a 2-3-fold molar excess in relation to the substrate. An excess of reducing agent is necessary for the complete conversion of aryl chloride. At the same time, the upper limit is limited to a 3-fold excess of zinc (magnesium, aluminum) in order to reduce the consumption of reducing agent.

 The proton source is used in a 2-3-fold molar excess with respect to the substrate.

 If necessary, remove several chlorine atoms from the aromatic ring, the amount of reducing agent and proton source must be increased, while maintaining a 2-3-fold molar excess for each chlorine atom to be removed.

 The amount of catalyst varies from 0.01 to 0.5 mol per mol of substrate, the optimal range is from 0.01 to 0.1 mol. When using less than 0.01 mol of the nickel compound per 1 mol of substrate, the time required for complete conversion of the substrate sharply increases, while using more than 0.1 mol of the catalyst leads to an unjustified increase in the consumption of reagents.

 It should be noted that the inert atmosphere is not required for the reaction.

 The non-obviousness of the proposed solution to the problem is illustrated by the available literature data. So, the literature does not describe the use of nickel compounds we offer as catalysts for the dechlorination of substituted chlorobenzenes, chlorobiphenyls and chloronaphthalenes.

The invention is illustrated by the following examples:
Example 1

0.242 g (0.001 mol) of nickel chloride hexahydrate, 0.156 g (0.001 mol) of 2,2'-bipyridyl, 4 ml of dimethylformamide and 1.1 g of water are placed in a flask equipped with a mechanical stirrer, reflux condenser, and an oil bath with an automatic thermostat. (1.1 ml, 0.06 mol). The mixture is heated to 70 ^° C. and stirred for 10 minutes until a green color appears.

3.9 g (0.06 mol) of zinc dust are added, the reaction mixture is stirred for another 30-40 minutes until a black color appears. 4.06 g (0.02 mol) of pentafluorochlorobenzene (7) are added, the reaction mixture is stirred at 70 ^° C. for 1 hour. The degree of substrate conversion is determined by HPLC. 3.03 g of pentafluorobenzene are distilled off from the reaction mixture, collecting a fraction with T _boiling. = 85-86 ^o C.

 Product yield 90%.

 Examples 2, 3 demonstrate the use of magnesium and aluminum as a reducing agent. Examples 2,3. The reaction is carried out under the conditions of Example 1, but magnesium (1.44 g, 0.06 mol) or aluminum (1.62 g, 0.06 mol) is used as a reducing agent. The results are shown in table 1.

 Examples 4 to 9 demonstrate the effect of the amount of reducing agent.

 Examples 4 to 9. The reaction is carried out under the conditions of example 1. The ratio of the reducing agent (zinc, or aluminum, or magnesium) / substrate is changed. The results are shown in table 2.

 Examples 10-18 demonstrate the effect of the amount of catalyst.

 Examples 10 to 18. The reaction is carried out under the conditions of example 1. Changes the amount of catalyst. The results are shown in table 3.

 Examples 19-23 demonstrate the possibility of using various sources of protons.

 Examples 19 to 23. The reaction is carried out under the conditions of example 1. The nature of the source of protons changes. The results are shown in table 4.

 Examples 24 to 28 demonstrate the possibility of using various inorganic nickel compounds to generate in situ complex compounds of nickel with 2,2'-bipyridyl.

 Examples 24 to 28. The reaction is carried out under the conditions of example 1. The inorganic nickel compound is changed. The results are shown in table 5.

 Examples 29-32 demonstrate the effect of temperature on the degree of conversion of the substrate.

 Examples 29 to 32. The reaction is carried out under the conditions of example 1. The temperature of the reaction is changed. The results are shown in table 6.

 Example 33 demonstrates the possibility of using nickel chloride and 1,10-phenanthroline complex compounds of nickel generated in situ from hexahydrate of nickel.

 Example 33

0.242 g (0.001 mol) of nickel chloride hexahydrate, 0.182 g (0.001 mol) of 1,10-phenanthroline, 4 ml of dimethylformamide and 1.1 g of water are placed in a flask equipped with a mechanical stirrer, reflux condenser, and an oil bath with an automatic temperature regulator. 1.1 ml, 0.06 mol). The mixture is heated to 70 ^° C. and stirred for 10 minutes until a green color appears.

3.9 g (0.06 mol) of zinc dust are added, the reaction mixture is stirred for another 30-40 minutes until a black color appears. 4.06 g (0.02 mol) of pentafluorochlorobenzene (7) are added, the reaction mixture is stirred at 70 ^° C. for 1 hour. The degree of substrate conversion is determined by HPLC. 3.10 g of pentafluorobenzene are distilled off from the reaction mixture, collecting a fraction with T _bales. = 85-86 ^o C.

 Yield 92%.

 Examples 34-37 demonstrate the possibility of using various solvents.

 Examples 34-37. The reaction is carried out under the conditions of example 33. The solvent is changed. The results are shown in table 7.

 Examples 58-78 demonstrate the possibility of using the proposed method for dechlorination of substituted chlorobenzenes (1-6, 8-14), chlorobiphenyls (15, 16) and chloronaphthalenes (17-19).

 Examples 38 to 38. The reaction is carried out under the conditions of example 33. The nature of the chloroaromatic compound is changed. The reaction products are isolated by conventional means. The results are shown in table 8.

Thus, the proposed method for dechlorination of substituted chloroaromatic compounds allows you to:
- to obtain products of dechlorination of substituted chloroaromatic compounds in high yields without the formation of by-products, which greatly simplifies the procedure for the isolation of target products;
- to avoid the use of significant quantities of phosphine complexes of Nickel, which can significantly reduce the amount of toxic reaction waste;
- abandon the use of an inert atmosphere for the reaction and, thus, simplify and reduce the cost of the process of dechlorination of substituted chloroaromatic compounds.

Claims (1)

The method of dechlorination of substituted chloroaromatic compounds of the formula

where R ¹ = R ² = R ³ = R ⁴ = R ⁵ = H (1);
R ¹ = R ² = R ⁴ = R ⁵ = H, R ³ = CH ₃ (2);
R ¹ = R ² = R ⁴ = R ⁵ = H, R ³ = OCH ₃ (3);
R ¹ = R ² = R ⁴ = R ⁵ = H, R ³ = C ₂ H ₅ (4);
R ² = R ³ = R ⁵ = H, R ¹ = R ⁴ = CH ₃ (5);
R ¹ = R ² = R ⁴ = R ⁵ = H; R ³ = NH ₂ (6);
R ¹ = R ² = R ³ = R ⁴ = R ⁵ = F (7);
R ¹ = R ² = R ³ = R ⁴ = R ⁵ = CH ₃ (8);
R ¹ = R ² = R ⁴ = R ⁵ = H, R ³ = Cl (9);
R ¹ = R ² = R ⁴ = R ⁵ = H, R ³ = COOH (10);
R ¹ = R ² = R ⁴ = R ⁵ = H, R ³ = COCH ₃ (11);
R ¹ = R ³ = R ⁵ = F, R ² = R ⁴ = Cl (12);
R ¹ = R ⁴ = H, R ² = R ³ = R ⁵ = Cl (13);
R ¹ = R ² = R ³ = R ⁴ = R ⁵ = Cl (14);
R ¹ = R ² = R ⁴ = R ⁵ = H, R ³ = C ₆ H ₄ Cl (15);
R ¹ = R ² = R ⁴ = R ⁵ = Cl, R ³ = C ₆ Cl ₅ (16);
R ¹ = R ² = R ³ = H, R ⁴ + R ⁵ = -CH = CH-CH = CH- (17);
R ¹ = R ² = R ⁵ = H, R ⁴ + R ³ = -CH = CH-CH = CH- (18);
R ¹ = R ² = R ³ = Cl, R ⁴ + R ⁵ = -CCl = CCl-CCl = CCl- (19)
reduction action (zinc, aluminum or magnesium) in the presence of a proton source and a catalyst consisting of a nickel salt and a ligand in an organic bipolar solvent medium, characterized in that 2,2'-bipyridyl and 1,10-phenanthroline are used as a ligand.

Images