WO2007064105A1

WO2007064105A1 - Novel process for preparation of 2,6-dialkylnaphthalene

Info

Publication number: WO2007064105A1
Application number: PCT/KR2006/004970
Authority: WO
Inventors: Young Gyu Kim; Byung Hyun Kim; Jong Gil Lee; Taeeun Yim
Original assignee: Seoul National University Industry Foundation
Priority date: 2005-11-29
Filing date: 2006-11-24
Publication date: 2007-06-07
Also published as: KR20070056470A; KR101140202B1

Abstract

The present invention relates to a novel method for preparing 2,6-dialkylnaphthalene with high selectivity and high yield using entirely novel starting materials through alkylation and cyclodehydration without necessitating separation or purification of isomers, which has been a problem of the conventional method, and particularly to a method comprising the steps of (a) preparing an intermediate by alkylating an aromatic compound with an alkene compound in an equivalent ratio in the presence of a catalyst and (b) preparing 2,6-dialkylnaphthalene through cyclodehydration of the intermediate.

Description

NOVEL PROCESS FOR PREPARATION OF 2,6-DIALKYLNAPHTHALENE

Technical Field

[1] The present invention relates to a novel method for preparing

2,6-dialkylnaphthalene with high selectivity and high yield without performing the separation of isomers, and particularly to a method comprising the steps of (a) preparing an intermediate by alkylating an aromatic compound with an alkene compound in an equivalent ratio in the presence of a catalyst and (b) preparing 2,6-dialkylnaphthalene through cyclodehydration of the intermediate. Background Art

[2] 2,6-Dimethylnaphthalene, which is 2,6-dialkylnaphthalene where two alkyl groups are methyl groups, is oxidized into 2,6-naphthalenedicarboxylic acid. Hereinafter, dimethylnaphthalene and naphthalenedicarboxylic acid are abbreviated as 'DMN' and 'NDCA', respectively.

[3] 2,6-NDCA, which is produced from 2,6-DMN, serves as a raw material for a high performance polyester resin, i.e. poly(ethylene naphthalate) (hereinafter referred to as 'PEN') and a liquid crystal polymer. At present, however, only a few chemical companies possess the technique for manufacturing 2,6-NDCA in the world.

[4] Due to the superior properties, PEN has been drawing much attention as a next- generation high-performance engineering plastic that may replace PET. As compared to PET, which has been widely used on a commercial scale, PEN shows better properties such as crystallinity, softening point, mechanical strength, heat resistance, chemical resistance, gas permeability, weather resistance and electrical insulating property.

[5] Therefore, if an efficient process for manufacturing 2,6-NDCA as a raw material of

PEN is developed and a low production cost and a sufficient amount of the raw material is secured by mass production, PEN will expand its application to fibers for a high-speed spinning, 8 mm tapes, video tapes, functional films as well as plastic bottles.

[6] There are several processes disclosed for the production of 2,6-NDCA. U.S. patent

No. 3,856,855 discloses a method for preparing NDCA comprising the step of oxidizing dimethylnaphthalene with molecular oxygen at a temperature of 100-160 °C under an oxygen partial pressure of 2-8 atmospheres in acetic acid of an amount of at least 4 weight parts per one weight part of dimethylnaphthalene in the presence of Co/ Mn/Br catalyst. [7] U.S. BP Amoco process is the most widely known among the conventional processes for the production of 2,6-DMN. BP Amoco process was successful in commercialization by employing the process comprising (a) the formation of alkenyl benzenes using ortho-xylene and 1,3-butadiene as starting materials through an alkenylation reaction, (b) the cyclization of the resulting alkenyl benzenes to form 1,5-DMT (1,5-dimethyltetralin; dimethyltetralin is referred to as 'DMT' hereinafter), (c) the dehydrogenation of the dimethyltetralin to form 1,5-DMN and (iv) the iso- merization of the resulting 1,5-DMN to the desired 2,6-DMN [D. L. Sikkenga; I. C. Zaenger; G. S. Williams, U.S. patent No. 5,030,781 (1991): D. L. Sikkenga; I. C. Zaenger; G. S. Williams, U.S. patent No. 5,118,892 (1992): L. D. Lillwitz; A. M. Dkarachewski, U.S. patent No. 5,198,594 (1993)].

[8] However, the BP Amoco process is complex and produces a large quantity of isomers of 2,6-DMN as by-products during the isomerizaton, thus lowering the overall yield while increasing the production cost of 2,6-DMN.

[9] Japanese companies, Teijin and Kobe-Mobil, attempted to produce 2,6-DMN using naphthalene or methylnaphthalene as a starting material through alkylation or acylation. However, the methods are found not suitable for mass production, considering the yield, life of catalysts and conditions of the reaction [K. Sumitani; K. Shimada, Japanese patent application No. 1992-013637 (1992): K. Sumitani; K. Shimada, Japanese patent application No. 1992-112839 (1992): M. Motoyuki; K.Yamamoto, U.S. patent No. 5,744,670 (1998)].

[10] Japanese company, Optatech, also attempted to produce 2,6-DMN using para - xylene and butene or butadiene in the presence of a base catalyst such as potassium through an alkylation reaction followed by cyclodehydrogenation. However, this method also has a limitation for commercialization due to its low yield [K. Vahteristo; E. Halme; S. Koskimies WO 97/02225 (1997): I. Kiricsi; S. Koskimies WO 97/24305 (1997): J. Jakkula; V. Niemi WO 97/30012 (1997)].

[11] In most of the conventional methods for preparing 2,6-DMN, a linear alkene compound such as l-(o-, m- orp-tolyl)pent-l-ene or l-(o-, m- orp-tolyl)pent-2-ene type as a starting material is cyclized in the presence of an acid catalyst followed by dehydrogenation and isomerization.

[12] However, the aforementioned process produces various isomers of DMN. Together with the DMN isomers, DMT and alkenyl benzene, which are not transformed into isomers of DMN, also exist as an impurity or a by-product, thereby requiring additional processes of isomerization and separation.

[13] Nonetheless, as the process for separating the aforementioned isomers is very complex and cost-consuming, there have been few processes suitable for the competitive commercialization developed so far despite the extensive attempts made to overcome the problems. [14] There is an urgent need for the development of a novel process for preparing

2,6-DMN that does not require the separation steps of various isomers. [15] As a way to fundamentally solve the aforementioned problems, the present invention aims to provide a method of preparing 2,6-DMN using entirely novel starting materials through alkylation and cyclodehydration.

Disclosure of Invention Technical Solution

[16] The present invention relates to a method of preparing 2,6-DMN comprising the steps of (a) preparing an intermediate of Formula (HI) by alkylating an aromatic compound of Formula (I) with an alkene of Formula (II) in an equivalent ratio in the presence of a catalyst; and (b) preparing 2,6-DMN of Formula (IV) through cyclodehydration of the intermediate prepared in the step (a):

[17]

( I ) ( II ) ( III ) ( IV)

[18] wherein R¹ is a linear, branched or cyclic C -C alkyl group; R² is a linear, branched or cyclic C -C alkyl group; R³ is O- Y, N-Y or S-Y; and R⁴ is O, N-Y or S wherein Y is a hydrogen atom or a heteroatom protecting group that may serves as a leaving group selected from the group consisting of alkyl, arylmethyl, alkylsilyl, alkoxycarbonyl, acyl, arylsulfonyl, alkylsulfonyl and dialkylphosphonyl groups.

[19] As used herein, an 'alkyl' group includes without limitation a linear or branched alkyl group, and preferably refers to a linear or branched C -C alkyl group, more preferably a C -C alkyl group.

[20] X is a halogen atom such as Cl, Br and I or O-Z wherein Z is a hydrogen atom or a heteroatom protecting group that may serve as a leaving group such as arylsulfonyl, alkylsulfonyl, perfluoroalkylsulfonyl and dialkylphosphonyl groups.

[21] Hereunder is provided a more detailed description of each step in the present invention.

[22] Hereunder is given a description of step (a), i.e. alkylation reaction.

[23] The alkylation reaction of the present invention is a process for preparing an intermediate of Formula (HI) by reacting an aromatic compound of Formula (I) and an alkene compound of Formula (II), which is schematically shown in Scheme 1.

[24] Scheme 1

[25]

( I ) ( II ) ( ill )

[26] wherein R¹, R², R³, R⁴ and X are as defined above, and preferably X is Cl or Br.

[27] According to Scheme 1 above, an aromatic compound of Formula (I) and an alkene compound of Formula (II) are reacted in the presence of a transition metal catalyst, to thereby provide an intermediate of Formula (HI). Phosphorus (P) or arsenic (As) based compound may optionally be used as a ligand. The catalyst is preferred to contain a transition metal as an active ingredient, and the transition metal may be selected from the group consisting of Pd, Pt, Ni, Rh, Ir, Ru, Fe, Co and a mixture thereof. Most preferably, the catalyst is a transition metal based catalyst containing at least one metal selected from Pd, Pt or Ni.

[28] The amount of the transition metal catalyst and the ligand is preferred to be

0.0001-100 mol%, respectively. When the amount is less than 0.0001 mol%, the reaction may not proceed to the end or the reaction rate may drastically decrease. When the amount is greater than 100 mol%, it may lead to an unnecessary economic loss and environmental pollution. More preferably, the amount of the transition metal catalyst and the ligand is 0.01-10 mol%, respectively. When a transition metal compound coordinated with ligands is used, the amount of the ligands is preferably more than twice the amount of the transition metal catalyst.

[29] The solvent used in the aforementioned reaction is preferably selected from the group consisting of acetonitrile, dimethylformamide, l-methyl-2-pyrrolidinone, acetic acid, dimethylsulfoxide, dimethylacetamide, methanol, ethanol, benzene, toluene, xylene, tetrahydrofuran and a mixture thereof. Moreover, the base is preferably an inorganic base selected from the group consisting of sodium acetate, sodium carbonate, sodium hydrogen bicarbonate, sodium phosphate, sodium hydroxide, lithium acetate, lithium carbonate, lithium bicarbonate, lithium phosphate, lithium hydroxide, potassium acetate, potassium carbonate, potassium bicarbonate, potassium phosphate, potassium hydroxide, cesium acetate, cesium carbonate, cesium hydroxide, calcium carbonate, calcium bicarbonate, calcium hydroxide, barium carbonate, barium hydroxide and a mixture thereof.

[30] The reaction is preferably performed for 1-48 hours, more preferably until the starting materials are completely consumed. The reaction temperature is maintained at between 0 °C and 250 °C throughout the reaction. When the temperature is higher than 250 °C, the reaction may proceed vigorously and produce a large amount of byproducts. When the temperature is lower than 0 °C, the reaction may not proceed. More preferably, the reaction temperature is maintained at between 80 °C and 150 °C. The reaction is performed under a pressure of from atmospheric pressure to 20 atmospheres. One skilled in the art may easily determine the temperature and the time of the reaction depending on the reaction pressure.

[31] As used herein, the yield is calculated as follows unless indicated otherwise:

[32] Yield (%) = (Moles of desired product / Moles of reactant) X 100

[33] Hereunder is given a description of the step (b), i.e. the cyclodehydration reaction.

[34] The cyclodehydration reaction of the present invention is a process for preparing

2,6-DMN of Formula (IV) by reacting an aldehyde intermediate of Formula (HI) in the presence of an acid catalyst, which is schematically shown in Scheme 2. [35] Scheme 2

[36]

( III ) ( IV )

[37] wherein R and R are as defined above, and preferably R and R are a methyl group. R is O.

[38] After a reactor is purged of remaining oxygen with inert gas such as argon or nitrogen, the intermediate of Formula (HI) is subject to cyclodehydration reaction in the presence of a cyclodehydration catalyst, thereby providing 2,6-DMN of Formula (IV).

[39] The catalyst used in the aforementioned reaction is preferably selected from the group consisting of a Lewis acid catalyst, an inorganic acid catalyst, a solid acid catalyst, an organic acid catalyst and a mixture thereof. Representative examples of the Lewis acid catalyst include but are not limited to ferrihalide(FeX n ), titanium halide

(TiX n ), titanium alkoxide (Ti(OR) n ), titanium oxide (TiO 2 ), aluminum halide (AlX n ), aluminum alkoxide (Al(OR) n ), tin halide (SnX n ), tin alkoxide (Sn(OR) n ), boron trihalide (BX n ), alkylborate (B(OR) n ), magnesium halide (MgX 2 ) and zinc halide (ZnX 2

). Representative examples of the inorganic acid catalyst include but are not limited to sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid, hydrobromic acid, phosphoric acid and hydriodic acid. The solid acid catalyst has an acidic group, and representative examples of the solid acid catalyst include but are not limited to Dowex resin, Amberlyst resin, Amberlite resin, Nafion resin and an acidic zeolite. Representative examples of the organic acid catalyst include but are not limited to acetic acid based acids such as acetic acid and trifuluoroacetic acid, and sulfonic acid based acids such as camphorsulfonic acid and para-toluenesulfonic acid. [40] The catalyst is preferably used in the amount of 0.01-1,000 mol%. When the amount is less than 0.01 mol%, the reaction may not proceed to the end or the reaction rate may drastically decrease. When the amount is higher than 1,000 mol%, it may lead to an unnecessary economic loss and environmental pollution. More preferably, the amount is 1-500 mol%.

[41] Meanwhile, the solvent used in the aforementioned reaction is selected from the group consisting of a hydrocarbon based solvent, a halogenated hydrocarbon based solvent, a heteroatom containing hydrocarbon based solvent and a mixture thereof. Preferably, the solvent is selected from the group consisting of toluene, xylene, chlorobenzene, bromobenzene, chlorotoluene, bromotoluene, dioxane, dichloroethane, trichloroethane, tetrachloroethane, pentachloroethane, hexachloroethane, di- bromoethane, tribromoethane, tetrabromoethane, pentabromoethane, hexabromoethane and a mixture thereof.

[42] The reaction temperature is preferably 50-300 °C. As shown in Scheme 1, when the temperature is higher than 300 °C, the reaction may proceed vigorously and produce of a large amount of by-products, and it also may lead to an economical loss. The reaction is preferably performed for from 10 minutes to 48 hours, more preferably until the starting materials are completely consumed. The reaction is performed under a pressure of from atmospheric pressure to 20 atmospheres. One skilled in the art may easily determine the temperature and the time of the reaction depending on the reaction pressure. The use of a microwave reactor may reduce the reaction time and lower the reaction temperature. Advantageous Effects

[43] The present invention shows high yield of 2,6-DMN without the separation and the isomerization steps that are required in the known processes and has other advantages with respect to the production cost and the entire process, which are attained by using novel starting materials that control the production of other isomers. [44] Moreover, as the catalysts used in all the reaction of the present invention may be recycled, the production cost may be further reduced.

Brief Description of the Drawings [45] Figure 1 shows a nuclear magnetic resonance (NMR) spectrum of an intermediate prepared by alkylating an aromatic compound with an alkene compound in the presence of a catalyst.

Best Mode for Carrying Out the Invention [46] The present invention is described more specifically by the following Examples.

Examples herein are meant only to illustrate the present invention, but in no way to limit the claimed invention. [47] Preparatory Example 1: Preparation of alkylated products from a mixture of 4-bromotoluene and 3-methyl-3-buten-l-ol using the Heck reaction

[48] 3.42 g (20 mmol) of 4-bromotoluene was dissolved by adding 50 mL of l-methyl-2-pyrrolidinone (NMP) in a high-pressure reactor. 4.49 mg (0.02 mmol) of palladium diacetate, 4.24 g of sodium carbonate and 3.44 g (40 mmol) of 3-methyl-3-buten-l-ol were added to the solution. The reaction temperature was maintained at between 80 °C and 150 °C, and the reaction was performed for 12-24 hours.

[49] After the termination of the reaction, the resulting mixture was subject to the separation of an organic layer using water and diethyl ether, followed by condensation of the organic layer. The desired product was obtained in a pure form using column chromatography or fractional distillation. The analysis of the product using H NMR (Figure 1) and gas chromatography shows that a pure aldehyde compound was produced as shown in Scheme 3 below. The amounts of the reactants, the kinds of the bases used and yields are presented in Table 1.

[50] Scheme 3 [51]

[52] Table 1

[53] Preparatory Example 2: Preparation of 2,6-DMN from the 3-methyl-4-(/ιara tolyl)butanal prepared in Preparatory Example 1 through cyclodehydration [54] 2 g of the aldehyde product prepared in the aforementioned alkylation reaction was dissolved in 1,1,2-trichloroethane. After 2 g of Amberlite^® IR 120 was added, the reaction was performed at 100-250 °C for 1-5 hours.

[55] After the termination of the reaction, the resulting mixture was filtered and the filtrate was subject to the condensation. The desired product, 2,6-DMN, was obtained in a pure form or along with a very small amount of 2,6-DMT by using column chromatography or fractional distillation.

[56] The product was identified as 2,6-DMN as shown in Scheme 4 below using ¹H NMR and gas chromatography. The amounts of the reactants, the kinds of the bases used and yields are presented in Table 2. [57] Scheme 4

[58]

0

Cata lyst , C l₂ CHCH₂CI -.

XXX 200 ⁰C 2 h I

[59] Table 2

[60] Example 1 [61] 3.42 g of 4-bromotoluene was dissolved in l-methyl-2-pyrrolidinone (NMP) in a high-pressure reactor, and 4.49 mg of palladium diacetate, 4.24 g of sodium carbonate and 3.44 g of 3-methyl-3-buten-l-ol 3.44 g were added to the solution. The reaction was performed at 80-150 °C under the atmospheric pressure for 12-24 hours.

[62] After the termination of the reaction, the resulting mixture was subject to the separation of an organic layer using water and diethyl ether, followed by condensation of the organic layer. The desired aldehyde product was obtained in pure form using column chromatography or fractional distillation as shown in Scheme 5 below (yield: 80%).

[63] 2 g of the aldehyde product prepared in the aforementioned alkylation reaction was dissolved in 1,1,2-trichloroethane. After 2 g of Amberlite^®IR 120 was added, the reaction was performed at 100-250 °C for 1-5 hours.

[64] After the termination of the reaction, the resulting mixture was filtered and the remaining liquor was subject to condensation. Pure 2,6-DMN, the desired cyclization product, was obtained with a yield of 83% by using column chromatography or fractional distillation as shown in Scheme 5 below. The product was identified as 2,6-DMN by using H NMR and gas chromatography.

[65] Scheme 5 [66] OH Vl Amberlite^® IR 1 20

^Pd( _NMK%^C°³ kAΛ. ^Cb^CHCH ₂ ^CI. ^B3%

2,6-D MN

[67] A method of the present invention may be modified into various embodiments within the technical ideas, and is in no way limited to the aforementioned Preparatory Examples and Examples. One skilled in the art may easily modify or apply the present invention within the technical ideas of the present invention. Therefore, the present invention shall not be limited to the aforementioned Preparatory Examples and Examples and the following Drawings, and shall be interpreted to include the following Claims and the equivalent thereto. Industrial Applicability

[68] The present invention relates to a novel method for preparing

2,6-dialkylnaphthalene with high selectivity and high yield using entirely novel starting materials through alkylation and cyclodehydration without necessitating separation or purification of isomers, which has been a problem of the conventional method, and particularly to a method comprising the steps of (a) preparing an intermediate by alkylating an aromatic compound with an alkene compound in an equivalent ratio in the presence of a catalyst and (b) preparing 2,6-dialkylnaphthalene through cyclodehydration of the intermediate.

Claims

[1] A method of preparing 2,6-DMN comprising the steps of: preparing an intermediate of Formula (III) by alkylating an aromatic compound of Formula (I) with an alkene of Formula (II) in an equivalent ratio in the presence of a catalyst; and preparing 2,6-DMN of Formula (IV) through cyclodehydration of the intermediate prepared in the step (a):

( I ) ( II ) ( II I ) ( IV) wherein R¹ is a linear, branched or cyclic C -C alkyl group; R² is a linear, branched or cyclic C -C alkyl group; R³ is O- Y, N-Y or S-Y; R⁴ is O, N-Y or S wherein Y is a hydrogen atom or a heteroatom protecting group that may serves as a leaving group selected from the group consisting of alkyl, arylmethyl, alkylsilyl, alkoxycarbonyl, acyl, arylsulfonyl, alkylsulfonyl and di- alkylphosphonyl groups; and X is a halogen atom selected from the group consisting of Cl, Br and I or O-Z wherein Z is a hydrogen atom or a heteroatom protecting group that may serve as a leaving group selected from the group consisting of arylsulfonyl, alkylsulfonyl, perfluoroalkylsulfonyl and di- alkylphosphonyl groups.

[2] The method of claim 1, wherein the R¹ is a linear or branched C -C alkyl group.

[3] The method of claim 1, wherein the R is a linear or branched C 1 -C 4 alkyl group.

[4] The method of claim 1, wherein the X is Cl, Br or I.

[5] The method of claim 1, wherein the step (a) is performed in a solvent selected from the group consisting of acetonitrile, dimethylformamide, l-methyl-2-pyrrolidinone, acetic acid, dimethylsulfoxide, dimethylacetamide, methanol, ethanol, benzene, toluene, xylene, tetrahydrofuran and a mixture thereof.

[6] The method of claim 1, wherein the catalyst is selected from the group consisting of sodium acetate, sodium carbonate, sodium hydrogen bicarbonate, sodium phosphate, sodium hydroxide, lithium acetate, lithium carbonate, lithium bicarbonate, lithium phosphate, lithium hydroxide, potassium acetate, potassium carbonate, potassium bicarbonate, potassium phosphate, potassium hydroxide, cesium acetate, cesium carbonate, cesium hydroxide, calcium carbonate, calcium bicarbonate, calcium hydroxide, barium carbonate, barium hydroxide and a mixture thereof.

[7] The method of claim 1, wherein the catalyst is a transition metal catalyst.

[8] The method of claim 7, wherein the transition metal catalyst is selected from the group consisting of Pd, Pt, Ni, Rh, Ir, Ru, Fe and Co.

[9] The method of claim 7, wherein the transition metal catalyst is selected from the group consisting of Pd, Pt and Ni.

[10] The method of claim 1, wherein the transition metal catalyst is a transition metal coordinated with phosphorus (P) or arsenic (As) based ligands.

[11] The method of claim 10, wherein the transition metal catalyst and the ligands are used in the amount of 0.0001-100 mol%, respectively.

[12] The method of claim 11, wherein the transition metal catalyst and the ligands are used in the amount of 0.01-10 mol%, respectively.

[13] The method of claim 1, wherein the step (a) is performed at a temperature of

0-250 °C.

[14] The method of claim 13, wherein the step (a) is performed at a temperature of

80-150 °C.

[15] The method of claim 1, wherein the step (a) is performed under a pressure of

1-20 atmospheres.

[16] The method of claim 1, wherein the step (b) is performed in the presence of a catalyst selected from the group consisting of a Lewis acid catalyst, an inorganic acid catalyst, a solid acid catalyst, an organic acid catalyst and a mixture thereof.

[17] The method of claim 16, wherein the Lewis acid catalyst is selected from the group consisting of ferrihalide (FeX n ), titanium halide (TiX n ), titanium alkoxide

(Ti(OR) n ), titanium oxide (TiO 2 ), aluminum halide (AlX n ), aluminum alkoxide

(Al(OR) n ), tin halide (SnX n ), tin alkoxide (Sn(OR) n ), boron trihalide (BX 3 ), alkylborate (B(OR) n ), magnesium halide (MgX 2 ), zinc halide (ZnX 2 ) and a mixture thereof.

[18] The method of claim 16, wherein the inorganic acid catalyst is selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid, hydrobromic acid, phosphoric acid, hydriodic acid and a mixture thereof.

[19] The method of claim 16, wherein the solid acid catalyst is a solid acid catalyst having an acidic group selected from the group consisting of Dowex resin, Amberlyst resin, Amberlite resin, Nafion resin and acidic zeolite.

[20] The method of claim 16, wherein the organic acid catalyst is selected from the group consisting of acetic acid based acids such as acetic acid and trifluoroacetic acid, and sulfonic acid based acids such as camphorsulfonic acid, para- toluenesulfonic acid, benzenesulfonic acid and a mixture thereof.

[21] The method of claim 16, wherein the amount of the catalyst used in the step (b) is 0.01-1,000 mol%.

[22] The method of claim 21, wherein the amount of the catalyst used in the step (b) is 1-500 mol%.

[23] The method of claim 1, wherein the step (b) is performed at a temperature of

50-300 °C.

[24] The method of claim 23, wherein the step (b) is performed at a temperature of

100-250 °C.

[25] The method of claim 1, wherein the step (b) is performed in a high-pressure reactor, a pressure tube or a microwave reactor.

[26] The method of claim 1, wherein the step (b) is performed in a solvent selected from the group consisting of a hydrocarbon based solvent, a halogenated hydrocarbon based solvent, a heteroatom-containing hydrocarbon based solvent and a mixture thereof.

[27] The method of claim 26, wherein the step (b) is performed in a solvent selected from the group consisting of toluene, xylene, chlorobenzene, bromobenzene, chlorotoluene, bromotoluene, dioxane, dichloroethane, trichloroethane, tetra- chloroethane, pentachloroethane, dibromoethane, tribromoethane, tetra- bromoethane, pentabromoethane and hexabromoethane.

[28] The method of claim 1, wherein the step (b) is performed under a pressure of

1-20 atmospheres.