CA1228077A - Process for preparing a sodium salt of a primary alkylamine - Google Patents

Abstract

Abstract The invention provides a process for preparing a sodium salt of a primary alkylamine comprising the step of reac-ting a sodium source directly with an alkylamine which has from 1 to about 20 carbon atoms in an organic solvent and in the presence of a catalytic amount of a pyridine base or a quinoline base.

Description

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This application is divided out of Application Serial No. ~25,411, filed on April 7, 1983. Application Serial No.
425,411 relates generally to the field of pyridine chemistry, and in particular to direct and substituted amination reactions of 3-alkylpyridines and to an improved process for synthesizing the

2-alkylamino-5-alkylpyridine and 2-amino-5-alkylpyridine products of such reactions.
In 1914, Chichibabin and Seide first reported that ~-picoline , or more commonly 2-methylpyridine , underwent direct amination in the free ~-position on the ring when treated with sodium amide in toluene at elevated temperatures. Chichibabin and Seide, J. Russ. Phys. Chem. Soc., 46 1216 (191~). This _ _ _ reaction was later extended by Chichibabin and his contemporaries to amination of many pyridine, quinoline and isoquinoline bases.
It has since been recognized as one of the more important and influential developments in pyridine chemistry, so much so that the reaction itself has become synonymous with the name of its principal discoverer. Its commercial importance should also not be discounted as, for example, -the 2-amino amination product o~

pyridine itself has become an enormously important and useful starting material for further synthesis in many areas.
The first attempt known to applicants to prepare a substituted aminopyridine during amination was reported by these same authors, Chichibabin and Seide, in the same 1914 paper, as the treatment of pyridine with the sodium salt of aniline repor-tedly gave 2-anilinopyridine in a very small yield. Substituted Chichibabin aminations have since been extended to a limited degree as, for example~ by Bergstrom et al who reportecl preparing 2-methylaminopyridine, 2-butylaminopyridine, 2-cyclc>hexylamino-pyrid~ne, 2-n-heptylaminopyridine, 2-methylaminoquinoline, 2-butylaminoquinoline ancl 2-cyclohexylaminoquinolille in yields ranging from 21-73~ by heating the eutectic mixture of sodamide and potassium aMide ~ith the BO èJ 7 ~~
heterocycle dissolved in the corresponcling primary aliphatic amine.
Bergstrom, Sturz, and Tracey, J. Orq. Chem., 11, 2~9 (1946).
Abramovitch and ~ogers reported that treatment of 3-picoline-1-oxide with N-phenylbenzimidoyl chloride gave predominently 2-(N-benzoylanilino)-5-methylpyridine which can be converted to 2-anilino-5-methylpyridine by hydrolysis. Abramovitch and Rogers, J. Orq. Chem., ~9, 1802 (197g).
Most prolific in the area of substituted Chichibabin aminations have been Kovacs and Vajda, who in a series of papers reported preparing 2-butylaminopyridine, 2-butylaminoquinoline, 2-dodecylaminopyridine, 2-cyclohexylaminopyridine, 2-benzylaminopyridine, 2-dimethylaminoethylamino-6-methylpycidine, 2-dimethylaminoethylaminopyridine 2-dimethylaminoethylaminoquinoline and 2-diethylaminoethylaminopyridine in yields ranging from 11-79%
by replacing the amide eutectic mixture used by Bergstrom et al.
with powdered sodium or potassium. In particular, their reported success in directly substituting an alkylamine at the 2-position of the pyridine ring involved heating pyridine, alpha-picoline or quinoline with the corresponding anhydrous primary alkylamine or aralkylamine in boiling toluene in the presence of powdered sodium or potassium. Kovacs and Vajda, Acta Chim. Acad. Sci. Hunq., 21, 445 (1959), C.A. 55, 1608b (1961); Kovacs and Vajda, Chem. Ind., 259 (1959); Kovacs and Vajda, Acta Chim. Acad. Sci. Hunq., 29, 2~5 (1961), C. A. 57, 5892h (1962): Kovacs and Vajda, ~cta Pharm. Hunq.
31, Suppl. 72 ~1961), C.A. 56, 5922e (1962).
Importantly, Kovacs and Vajda reported no reaction when only the alkylamine was heated with powdered sodium in toluene in an attempted preliminary reaction. This indicated no formation of the sodium alkylamide. They also reported low yields of the sodium salt even after long reaction times when sodamide was substituted for powdered sodium in the same reaction. They concluded that the ~ 8(:~'7 condition for a successful substituted amination reaction required that the base and the amine react simultaneously with the powdered sodium. Vajda and Kovacs, Rec. Trav. Chim., ~0, 47 (1961).
Moreover, under these conditions considerable amounts of dipyridyls and tarry materials are also formed because of competing reactions of sodium with the heterocyclic compound. Other efforts to prepare sodium salts o~ alkylamines have reported similar marginal to poor success, or in the case of one author, required a stable sodium dispersion at very low temperatures using hazardous liquid butadiene. DePree, U. S. Patent No. 2,799.705 (1957). Without any efficient, practicable method for preparing these salts, the accepted prac~tice at this time for substitutin~ a heterocyclic base during a substituted Chichibabin amination remains the Kovacs and Vajda procedure of reacting the base and the amine simultaneously with powdered sodium o~ potassium.
~ eferring specifically to 3-substituted pyridines, applicants are unaware of any prior attempted substituted Chichibabin aminations o~ these compounds . . . successful or not. It is known that an appreciable number of these bases, and particularly tte

3-alkyl derivatives, undergo simple amination with sodamide to produce predominantly a 2-amino-3-alkylpyridine reaction product ("2,3-isomer"), and to a much lesser extent a 2-amino-5--alkylpyridine ("2,5-isomer"). For example, the Chichibabin amination of 3-methylpyridille, also known as 3-- or beta--picoline, with sodarnide has been reported to yield these 2,3-and 2,5-isomers in a ratio of 10.5:1. Abramovitch, Ad~an.
.L_ Chem., 6, 29~ (1966). This is extremely unfortunate as the 2,5-isomers are mucll preLerred because of their use~ulness as startin~ materials and inteLmediates for the preparation o herbicides, insectic~def, and pharrmaceuticals. The 2,3--isomers aLe co:npaLatively o little or no use at this time, and their hi~h yields significantly add to the expense of the process both in starting material consumed and in disposal of the 2,3-isomers. A
way to improve the yield of these 2,5-isomer amination products, and of 2-amino-5-methylpyridine as being commercially most impor-tant at this time, is greatly needed.
Application Serial No. 425,411 addresses this need by providing an improved process for preparing these 2,5-isomer products which involves subjecting 3-substituted bases to direct alkylamination in a substituted Chichibabin reaction. In parti-cular, one embodiment involves the step of reactin~ a 3-alkyl-pyridine directly with a sodium alkylamide, wherein the alkyl group in each has from 1 to 20 carbon atoms based on experiments performed to date. The reaction proceeds by reversin~ the pre-viously accepted high 2,3 :2,5- isomer ratio and by selectively producing greatly improved yields of the much-preferred 2-alkyl-amino-5-alkylpyridine ("2,5-alkylated isomer") reaction products.
The present application is directed to the preparation of these sodium salts of primary alkylamines, and the discovery that these salts are preferably preformed prior to the alkylami-nation reaction. In particular, applicants have discovered asignificantly improved and efficient process for preparing these salts in reasonable times by reacting the sodium source directly with the alkylamine which has from 1 to about 20 carbon atoms in an organic solvent and in the presence of a catalytic amount of a pyridine base or quinoline base, Most preferred as catalysts, at least at this time, are 3- and 4-alkylp~idines~nd their 3,3'-and 4,4'-dialkyl-2,2'-bipyridyl dimeric equivalents, in which each alkyl ~roup has from 1 to about 6 carbon atoms.
In a preferred form, applicants' alkyla~ination is accomplished by addinq the selected 3-alkylpyridine base to a stirred dispersion of the sodium alkylamide which is heated to at least 100C in an orcJanic sol~en. such as toluene. The sodium alkylamide had been earlier pre~ormed in the same vessel by adding the alkylamine to a heated sodium dispersion in toluene also containing a small amount o catalyst identified above. Subseguen~ isolation of the 2-alkylamino-5-alkylpyridine products has shown significant yields well in excess of 50% for some bases and has resulted in 2,5-:2,3-akylated isomer ratios in excess of 10:1. These 2,5-alkylated isomers have useful biocidal properties, and are readily dealkylated in a subsequent step of applicants' invention to the more common 2-amino-s-alkylpyridine form which has known uses in ~he preparation of herbicides~ insecticides and pharmaceuticals.
Related objects and advantages of the present invention will be apparent from the follo~ing description.
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to preferred embodiments of applicants' invention and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intenaed, such alterations and further modifications of the principles of the invention as described herein being contemplated as would normally occur to one skilled in the art to which the invention relates.
In its broadened form, one embodiment of applicants' invention was the discovery that significant and surprising results are achieved by subjecting various 3-substituted pyridines to direct alkylaminations with the sodium salt of various alkylamines in a substituted Chichibabin reaction. In so doing, applicants discovered that unlike aminations of such bases with sodamide, which produce high 2,3--:2,5- isomer ratios, their reaction reversed this ratio and selectively produced greatly improved yields of the much-preferred 2,5--isomer p~oducts in their alkylated amino forms.
Unlike Vajda and Kovacs, applicants found that simultaneous reaction of the base with sodium and the amine is not required or successful ~ 8Q~,t;~ ~

substitution. On the contrary, applicants' work has shown it is preferred to preform the sodium salt of the alkylamine by an improved process which involves reacting the components in the presenee of a catalytic agent described in detail below. In addition, applicants have discovered an improved process for dealkylating the 2-alkylamino-5-alkylpyridine products of their alkylamination reactions as also described below and in the specific examples which follow.
In its more preerre~ form, the alkylamination reaction was carried out in an organic solvent at a temperature appropriate for the 3-alkylpyridine used, and continued for a period of at least about l hour or until substantial alkylamination had occurred. No particular temperature or time period was required to achieve the successful and beneficial results of applicants' discovery. Rather, temperature and time can be and were varied depending upon the specific reactants and equipment used and upon the pereent yield desired just as in standard Chichibabin aminations. From applicants' experience, a yield of about 50% or more of the 2,5-alkylated isomer produet is desirable for the proeess to be commercially practicable, although substantially lower yields of about 25% or less ean be eommercially important for certain bases.
In its most preferred ~orm, this reacting step further inel-~decl the steps of pre~orming the sodium salt of a primary alky1amine in an inert organic so1vent, bringing the resulting dispersion to d temperature of at least about 100C, adding an amount of selected ~-alkylpyridine base to the heated dispersion, and maintaininc; the dispersion at or al-ove tllir; temperature while the base was added and for such adclitional time as was desired L-or the reaction ~o proceed. To1uene wa; the solverlt oL choice, and the ~pecific tempe~ature and time nsed were not critical to the benetits o~
reaction. ~or e~a~ , he<ltirl~J was continuecl for periods of about `~

to in excess of 15 hours and at temperatures of about 100C to over 140C as shown in the specific examples set forth below.
~ pplicants' preferred method of preforming the 60dium salt of a chosen alkylamine involved reacting a sodium source with a selected primary alkylamine in ~he presence of a catalytic amount of a pyridine base or quinoline base. More specifically, a sodium dispersion was first prepared in a vessel by rapidly stirring an amount of sodium in an organic solvent such as toluene at a temperature of between about 100-120C. This preferably took place under an inert nitrogen atmosphere. wit~l the dispersion prepared, a small amount of catalyst was added with agitation, and the temperature of the dispersion was brought to reflux at which time the selected alkylamine was added. The catalyst of choice thus fac was 4-picoline. ~efluxiIlg was continued for a period of time sufficient to permit substantial formation of the sodium salt. As with the alkylamination reaction, no specific temperature or period of time was essential to the reaction. The impo{tant consideration was the formation of a substantial amount of the sodium salt for subsequent alkylamination of the pyridine base. Accordingly, reaction times were varied from about 1 to more than 12 hours, and temperatures were varied widely within the refluxing ranye. At the point when salt formation was sufficient, the pyridine base was added and the alkylamination step took place.
Following heating the 3-substituted base in the preformed salt (lispersion to cause alkylamination to occur, the produced 2,5-alkylated isomer was isolated for subsequent use. In its most preferred form, this isolatiny step involved cooling and hydrolyzing the mixture a~ter thP reacting step was complete, followed by separating and ~ractionating the organic phase to obtain the individual 2--alkylamiI)o-5--alkylpyridine and 2-alkylamino--3 alkylpyridine i50mers. The 2,5-alkylated isomer was ~ZZ~7 ~ ~
found to have useful biocidal properties although applicants' most preferred embodiment included the additional step of dealkylating the recovered 2,5-alkylated isomer product.
The preferred dealkylation method involved the discovery that the 2,5- and 2,3-alkylated isomer bases dealkylated smoothly and in excellent yield when their hydrohalide salts were ~eated in a stream of hydrogen halide gas to release the dealkylated base and an alkyl halide and/or a corresponding olefin. ~ccordingly, the most preferred dealkylation procedure to date included reacting the isolated Z,S-alkylated product with hydrobromic acid or hydriodic acid to produce the dealkylated material. Applicants' testing has also shown that beneficial results are achieved when an amount of pyridine hydrohalide salt was combined with ~:he hydrohalide salt of the 2,5-alkylated base prior to treatment with ~he hydrobromic or hydriodic acid. The temperature maintained during the dealkylation step ranged between about 165-275C and the time involved between about 1-26 hours depending, as before, on the specific reactants used and the percent conversion desired.
Referring now to the particular reactants used thus far, and to the yields obtained, applicants' work to date has concentrated on 3-alkylpyridines and on the sodium salts of primary alkylamines, the alkyl groups in each case ranging from 1 to about 20 carbon atoms.
The mofit preferred starting materials have been 3-picoline and sodium butylamide, which have resulted in product yields over 70~
and in a 2,5-:2,3-alkylated isomer ratio in excess of 10:1 in both the 2-alkylamino and 2-amino forms. The catalyst used in preforming the sodium salt has been a pyridine base or a quinoline base compound, and more preferably a sin41e compound or a mixture selected from the g~ou~ consi~ting of 3- and 9-alkylpyridines, 3.3'-and 9,9~-dialkyl-2,2 -bipyridyls, 3- and 9-arylalkylpyridines and 3 and 9-alkyl-luinolirles, in which each alkyl group has from 1 to about ~L2~8~7 6 carbon atoms and each aryl group has from 6 to about 12 carbon atoms. From experiments to date, even more preferred as the catalyst has been a single compound or a mixture selected from the ~roup consisting of 3- and 4-alkylpyridines and their dimeric equivalents in which each alkyl group has from l to about 6 car-bon atoms, with 4-picoline being the catalyst of choice.
For the purpose of further understanding the results of applicants' work to date and the scope and breadth of the inventions of this application and of related Application Serial No. 425,411, reference is now made to the specific examples and -table which follow:
Example l Butylamination of 3-Picoline , . . .. . . ~ .. .
A sodium dispersion was prepared by stirrin~, under a nitrogen atmosphere, 24g (1.04 gram atom) of sodium in 300 cc of toluene at 100-105C. The dispersion was made in a liter, three-neck, round bottom flask, equipped with a hiqh speed (lO,000 rpm) impeller capa~le of imparting high shearing action, reflux con-denser, thermometer and dropping funnel. ~fter the sodium was dispersed, 8 cc of 3-picoline was added and high speed a~itation was continued about 0.5 hour until the color of the dispersion turned brown (evidence of catalyst ~ormation). At this point, high speed agitation was replaced with slow speed paddle ayita--tion. The dispersion was brought to re~lux temperature and 73 g (l mole) of butylamine was added dropwise in the course of 2 hours, Hydrogen was evolved indicatin~ the forma-tion of sodium butylamide. Refluxin~ was continued for 1.7 hours, when 93 ~ (l mole) of 3-picoline was added over 1.5 hours (hydro~en evolu~ion).

The mixture was refluxed an additional 15 hours, after which time it was cooled and hydrolyzed with 150 cc of water. The toluene phase was separated and distilled to ~ive 12~.2 ~ boilin~ 162-196C at 60 mm _ 9 ~

(freezing point 37.3C). A GLC analysis showed 85.6%
2-butylamino-5-methylpyridine and ,3.6% 2-butylamino-3-methylpyridine (ratio of isomers 9.95:1). Yield of both isomers, 71.3%. The recovered 2-butylamino-5-methylpyridine was found to have useful biocidal properties.

Example 2 3utylam;nation of 3-Picoline ~ sodium dispersion of Z3 g of sodium (1 gram atom~ in 350 cc of toluene was prepared as described in Example 1. A catalyst was formed from 8 cc of 4-picoline. At reflux temperature, 73 g (1 mole) of butylamine was added over 2.5 hours. After an additional 3.2 hours of reflux, 93 g (1 mole) of 3-picoline was added during the course of 1.1 hours. After the picoline addition, refluxing was col~tinued for 0.6 hours before cooling and hydrolyzing with 100 cc of water. The toluene phase was sepaLated and distilled to give 123.5 g boiling 170C at 52 mm to 177C at 37 mm (freezing point 37.8C). The distillate was analyzed by GLC to show 90.3%
2-butylamino-5--methylpyridine and 5.6% 2-butylamino-3-methylpyridine (ratio of isomers 16.1:1). Yield of both isomers, 72.2%.

Exampl_ ~utylamination of 3-Picoline .
A sodium dispersion o~ 24 g sodium (1.04 gram atom) in 300 cc toluene was prepared as described in Example 1. A catalyst was formed by adding 4 cc of ~-(3-phenylpropyl) pyridine. Butylamine (73 g, 1 mole) was added at reflux temperature over 1.5 hours.
After 12 hours of additional refluxing, 93 g (1 mole) of 3-picoline was added over 0.35 hours. Refluxing cont;nued for 1.3 hours when the reaction mixture was cooled and hydrolyzed with 150 cc of water. The toluene phase was separated and distilled to give 11~.2 ~ 28~
g boiling 162-212C at ~35 mm (freezillg point 37.5C). The distillate was shown by GLC to contain 87.1%
2-butylamino-5-methylpyridine and 6.8% 2-butylamino-3-methylpyridine (ratio of isomers 12.8:1). Yield of both isomers, 65.4%.

Example 4 Butylamination of 3-Picoline A sodium dispersion of 48 g sodium (2.09 gram atoms) in 350 cc toluene was prepared as described in Example 1. A catalyst was formed by adding 8 cc of ~-propylpyridine. Butylamine (146 g, 2 moles) was added at reflux temperature over ~ hours. After refluxing for an additional 4 hours, 186 g (2 moles) of 3-picoline was added in the coucse of 2 hours. Refluxing continued for 3 more hours before the reaction mixture was cooled and hydrolyzed wi~h 200 cc of water. The toluene phase was separated and distilled to give 256.8 g boiling 155-199C at 48 mm (freezing point 38.0C). ~y GLC
the distillate was 85.~3~ 2-butylamino-S-methylpyridine and 7.0%
2-butylamino-3-methylpyridine (ratio of isomers 12.3:1). Yield of both isomers, 72.7%.

Example 5 Butylamination of 3-Picoline A mixture of 24g (1 mole) of sodium hydride and 400cc of toluene was stirred in a liter, 3 neck flask, and heated to re1ux.
~ddition of 73g (1 mole) of butylamine was started but the rate of formation of the sodium salt of butylamine was not practical as evidenced by the extremely slow rate of hydrogen evolution. The butylamine addition was stopped and 2 cc of 4-picoline was added.

The picoline acted a~ a catalyst for the formation of sodium butylamide as moderate hydrogen evolution was now observed. The amine addition was rcsllmed, taking about 1 hour. Kefluxing was continued for 7.5 houes before 93g (1 mole) of 3-picoline was added over 1.5 hours. The reaction mixture was refluxed 1 additional hour, cooled and hydrolyzed with 150 cc of water. The toluene phase was separated and distilled to give 8~.lg boiling 154-177C at 23 mm. A GLC analysis showed 91.5% 2-butylamino-5-methylpyridine and

4.9% 2-butylamino-3-methylpyridine (ratio of isomers 18.7/1). Yield of both isomers, 49.4%.

Exarnples 6-15 Alkylamination of 3-Alkvlpyridines Procedures similar to those in Example 1 were followed for the alkylaminations of the respective 3-alkylpyridines and sodium salts of alkylamines identified in the Table which follows. Reaction times and temperatures are also given for each Example. The sodium salts had in each case been preformed in situ using ~he catalyst identified in the Table. The products in each Example were isolated and analysed, and the results were as stated in the Table. The 2-alkylamino-5-alkylpyridine isomer recovered in each Example, also referred to as the 2,5-alkylated isomer for the purpose of this application, was found to have useful biocidal properties similar to the 2-butylamino~5--methylpyridine produc~ in Examples 1-5.

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8(37~7' Example 16 Dealkvlation of 2-Butylamino-5-methvlpyridine A 500 cc, three-neck, round bottom flask was fitted with a stirrer, thermometer, dropping funnel and a condenser for distillation. In the flask were cautiously mixed 199.9 g tl.22 mole) of 2-butylamino-5-met~lylpyridine prepared by the procedure of Example 1 and an equivalent amount of 98% hydrobromic acid. The solution was distilled until most of the water was removed and the liquid temperature reached 210C. Concentrated hydrobromic acid was added dropwise at a rate of ~8 g per hour to the molten 2-butylamino-5-methylpyridine hydrobromide, maintaining a liquid temperature within a range of 210-225C. Dealkylation took place during the hydrobromic acid addition with the formation of bromobutanes which were continuously distilled along with excess aqueous hydrogen bromide. There was also a continous evolution of noncondensable 2-butene. The two-phase condensate was separated and the aqueous acid phase was recycled until the specific gravity dropped to about 1.2. The process was stopped after 6.5 hours when there was no longer any evidence of bromobutanes in the distillate.
P~ total of 106.2 g (0.7t3 mole) of bromobutanes was collected and had the composition of 83.2% l-bromobutane and 16.8~ 2-bromobutane.
material balance on hydrogen bromide showed that there was 2.04 moles consumed during the dealkylation.
~ hen the process was finished, the molten 2-amino 5-methylpyridine hydrobromide was cooled slightly and 50 cc of water was slowly added. Cooling was continued and the solution was made basic Wit~l e~cess 50~ caustic. The product was extracted with 150 cc of toluen~ anci (listille(l to give 129.~3 g o~
2-amino S-metllylE)ycidine boilin(l 156--15l at B2 mm (Lree~ing point 75.3C). Yield, 9B.3~. 'I'he recovered 2-amino--5-methylpycidine was then used suceesstlllly a<: ~ fica~tin(3 material and inte~mediate for 1~

~ ~X807'7 the preparation of herbicides, insecticides and pharmaceuticals.

Example 17 Dealkylation of 2-Butylamino-5-methYlPYridine This example shows that a practical rate of dealkylation was obtained at lower temperature when pyridine hydrobromide was included with 2-butylamino-5-methylpyridine hydrobromide.
In the same equipment as decribed in Example 16. except that a peristaltic pump was used to control the rate of hydrobromic acid addition, a mixture of 1 mole of 2-butylamino-5-methylpyridine hydrobromide and 1 mole of pyridine hydrobromide was treated with hydrobromic acid in much the same manner as described in Example 16, except that the dealkylation temperature was held at 1~5C. After 26.5 hours, there was obtained 0.79 mole of 2-amino-5-methylpyridine, 0.14 mole of 2-butylamino-5-methylpyridine and 0.75 mole of bromobutanes. Yield, based on recovered 2-butylamino-5-methylpyridine, 91.9%. There was also recovered 96%
of the pyridine used in the dealkylation reaction.

Examples 18-27 DealkYlation of 2-Alkylamino-5-Alkylpvridines In each of Examples 18-27, a different one of the 2,5--alkylated isomer products rom Examples 6-15 as appear in the Table was dealkylated using the same procedure described in Example 16 for temperatures between about 165-275C and for periods of time ranging from about 1 '~o over 25 hours. The recovered 2-amino-5-alkylpyridine products were each found useful in herbicidal, insecticidal and pharmaceutical applications just as the 2-amino-S--Methylpyridine product in Examples 16 and 17.

Claims (6)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for preparing a sodium salt of a primary alkylamine comprising the step of reacting a sodium source direc-tly with the alkylamine which has from 1 to about 20 carbon atoms in an organic solvent and in the presence of a catalytic amount of a pyridine base or a quinoline base.

2. The process in claim 1 in which said reacting is at a temperature between about 100-120°C.

3. The process in claim 2 in which the catalyst is a single compound or a mixture selected from the group consisting of 3- and 4-alkylpyridines, 3,3'- and 4,4'-dialkyl-2,2'bipyridyls, 3- and 4-arylalkylpyridines and 3- and 4-alkylquinolines, in which eaeh alkyl group has from 1 to about 6 carbon atoms and each aryl group has from 6 to about 12 carbon atoms.

4. The process in claim 2 in which the catalyst is a single compound or a mixture selected from the group consisting of 3- and 4-alkylpyridines and their dimeric equivalents in which each alkyl group has from 1 to about 6 carbon atoms.

5. The process in claim 4 in which the catalyst is 4-picoline.

6. The process in claim 5 in which the sodium source is metallic sodium and the solvent is toluene.