NO126273B - - Google Patents

Description

Procedure for the production of organic

substituted sodium aluminum hydrides.

The present invention relates to a method for the production of organically substituted sodium aluminum hydrides.

Certain organically substituted sodium aluminum hydrides, e.g. sodium aluminum methoxyhydride, -methoxyhydride and -aryloxyhydrides are known and used in organic chemistry as specific reducing agents. It is e.g. possible by using these compounds as reducing agents to reduce aldehydes, ketones, organic acid esters and chlorides to alcohols, nitro compounds to amines and nitriles to aldehydes. These compounds can also be advantageously used as a dehalogenating agent.

Various methods for producing these compounds are known.

One of the difficulties encountered in the preparation of these compounds and in their use is due to the fact that they are only soluble in a small number of organic solvents, such as e.g. in diethyl ether. However, the compounds are not soluble in solvents which are more readily available and which also pose less risk when handling. It is e.g. thus not possible to dissolve the above-mentioned organically substituted sodium hydrides in benzene.

This limited solubility presents difficulties and dangers both in the manufacture and use of the products.

Other hydrides, e.g. decaboranes, are soluble in non-polar solvents, but solutions of these hydrides have no reducing properties.

From British patent document 878,137 it is known to prepare usable reducing agents by treating alkoxy or aryloxy aluminum halides with alkali hydrides in the presence of inert solvents. By this process, some of the present process compounds can be prepared, but in quite a different way, namely starting from the halogen alcoholates of aluminum and reacting these with alkali hydrides. Whereas previously from alkali hydride and aluminum alcoholate it was only possible to prepare the monohydridotrialkoxy compounds, according to the patent, by using aluminum haloalcoholates, it is also possible to prepare dihydridodialkoxy and trihydridomonoalkoxy derivatives. A major disadvantage, however, lies in the fact that as a by-product you get a large amount of sodium chloride which is excreted in a very finely divided, poorly filterable state, and which contains large amounts of mother liquor and product. This disadvantage is avoided by the present method.

From Belgian patent 653.8l8, it is known to prepare NaAlH^Z by starting from NaZ, Al and H2, and this involves a hydration of aluminum to form aluminum hydride AlH^, which upon further reaction with NaZ gives the final compound. This reaction" can be accelerated catalytically by a small amount of an alkylaluminum compound, and triethylaluminum is mentioned here, for example. This compound is mentioned here in particular as triethylaluminum easily undergoes oxidation to form aluminum alcoholates. The method according to this patent thus does not preempt the present method either.

Norwegian patent 123,642 relates to a method for the production of complex sodium aluminum hydrides of the general formula:

where x is 1, 2 or 3, and Z is lower alkyloxy, lower alkylaminoalkyloxy, diloweralkylaminoalkyloxy, phenoxy, optionally cyclized etheralkyloxy or polyetheralkyloxy, by reacting aluminum and sodium and/or optionally sodium hydride with at least one of the Z-substituted compounds HZ, NaZ, AlZ^ and NaAlZ^, where Z is as stated above, in amounts corresponding to the composition of the desired product, in a pressure vessel under hydrogen thrust, the closed vessel being heated to 100° - 190°C.

The present invention therefore aims to overcome the above-mentioned difficulties and disadvantages, by providing a method for the production of complex, organically substituted sodium aluminum hydrides with the general formula:

where x is 1, 2 or 3, and Z is a methoxy, ethoxy or propoxy group or a group Q derived by removal of active hydrogen from

(1) tetrahydrofurfuryl-lower alkanols,

(2) tetrahydropyranyl-lower alkanols,

(3) ether alcohols of the formula: HO-(CH2)n-OR', where R' is alkyl of 1-4 carbon atoms or alkaryl of 6-8 carbon atoms, and n is 2, 3 or 4, (4) polyether alcohols obtained by condensation of ether alcohols and diols with elimination of water, with the formula: HO(CH2)zO(CH2)wOR<»>where z and w, which are the same or different, are 2, 3 or 4, and R<*>are as above indicated, or

(5) amino alcohols of the general formula R2N(CH2)zOH, where z is 2, 3 or 4, and R an alkyl- or alkoxy-

alkyl group where the alkyl group contains 1-4 carbon atoms.

by reacting a sodium hydride with an aluminum trialcoholate at an elevated temperature in the presence of an organic solvent, and the method is characterized in that trisodium aluminum hexahydride, Na^AlHg, is reacted with a compound of the formula AlZ^ optionally in the presence of NaZ and/or AlCl^, where Z is as stated above.

The starting material, Na^AlHg, can e.g. is produced by the method described in Norwegian patent no. 116,036.

Compounds with the general formula AlZ^ and also with the general formula NaZ which can also be used as an additional reaction agent which will be explained in detail later, can be produced by reacting the alcohol in question with the metal, i.e. sodium or aluminum or with the respective hydrides, i.e. sodium hydride or aluminum hydride. There are no difficulties associated with the preparation of derivatives which are substituted with a dialkylamino and alkylamino group.

The NaZ compounds produced in this way are insoluble

in the reaction medium so that a suspension must be prepared.

Before these compounds are used in the above-described method according to the present invention, which e.g. can be carried out according to the reaction equations described below 3~5> the NaZ compounds must be separated from the suspension by filtration and subsequent drying. The dried product thus obtained can be used directly as starting material for the present method without further purification. Impurities that may be present e.g. in the form of metallic sodium, does not interfere with the reaction as these impurities are insoluble in the reaction medium, while the end products obtained by the present method are soluble in the relevant reaction medium. If, however, a compound of the type NaZ is produced using NaH as starting material, and the thus produced NaZ may therefore contain a residue of NaH, it is in several cases advantageous in the present method to increase the amount of sodium aluminum hydride and of A1Z 50 beyond the theoretical necessary quantity.

The production of alcoholates and aminoalcoholates of the type AlZ-j where Z is Q is also simple. In the production of all these derivatives, common methods can be used which start with aluminum or aluminum hydride and the corresponding alcohol, or amino alcohol with the formula QH, whereby the latter compound can be easily separated from the product AlQ^ by removing solvent. Finally, the product is dried in vacuum. All sodium aluminum hydrides prepared in accordance with the present invention are soluble in hydrocarbons and ethers. The unreacted aluminum or aluminum hydride can be easily removed by filtration before the end product is isolated.

Another advantageous method for producing aluminum alcoholates of the AIQ^ type is based on the following reaction equations:

It is preferred to use an excess of OH and to carry out the reaction while simultaneously removing CH^OH or ROH, which is an alcohol whose boiling point must be lower than that of QH. This is generally the case. The removal of CH^OH^OH) can be carried out in the usual way by means of a distillation column.

The starting products for carrying out the reaction, i.e. the aluminum alcoholates, can easily be produced in a pure state also on a technical scale. It is particularly preferred to start with A^OCH^).^as this compound e.g. is insoluble in hydrocarbons, thereby greatly facilitating the separation of an unreacted amount of the reaction mixture. The reaction product AlQ^ can be easily isolated by removing the solvent and excess QH.

The present method can be carried out in accordance with the following reaction equations:

It is known that sodium alcoholates and aluminum alcoholates react in such a way that complex alcoholates are formed according to the reaction equation:

where X is alkyl or aryl. The only condition for conversion of the reaction is solubility. A^OX)^ and the product NaAl(OX)^ must be soluble in the solvents used. The alcoholates of the type AlQ^ are generally more easily soluble in ethers and aromatic hydrocarbons than the alcoholates of the type Na(OX) .A^OX)^», where X is as indicated above. They occur as intermediate products according to reaction equations 3-5.

The liquid reaction medium in which the above-described reactions according to the present invention are carried out preferably belongs to the group of hydrocarbons and ethers which at atmospheric pressure have a lower boiling point than the decomposition temperature of the substituted sodium aluminum hydrides to be produced.

In a suitable method, the reaction is carried out under reflux distillation at the boiling point of the reaction mixture. It is preferred to use benzene or toluene as a reaction medium, but the reaction media described above can also be used.

The organically substituted sodium aluminum hydrides according to the present invention can be used in solution as a reducing agent, and as catalysts for the direct synthesis of complex sodium aluminum hydrides from free elements, i.e. sodium, aluminum and hydrogen (cf. Norwegian patent 116,036).

These substituted, complex sodium aluminum hydrides can

in non-polar media, e.g. in benzene, reduce organic acid derivatives, ketones and aldehydes to alcohols in the same way and to the same extent as unsubstituted, complex aluminum hydrides in ether. In contrast to the known complex aluminum hydrides can

they also dehalogenate alkyl and aryl halides and further reduce nitro compounds to azo compounds. All previously mentioned reactions can be carried out both in ethers and in non-polar media.

The following examples serve to describe the invention in more detail.

Example 1

In an apparatus which will be described in more detail in Example 2, 2.1 g of an 80% (0.0164 mol) solution of Na^AlHg and 50 ml of benzene were introduced. The mixture was boiled with a reflux condenser and 8.27 g (0.0328 mol) Al(OCH 2 CH 2 OCH 3 ) 3 dissolved in 10 ml of benzene was added dropwise. The reaction mixture was boiled for an additional 30 minutes with stirring. After the filtration and evaporation of the solvent, 9.36 g of NaAlH2(OCH2CH2OCH3)2 were obtained, i.e. 94.1% of the theoretical.

The starting compound Al(OCH2CH2OCH3)3Dle prepared in accordance with the following reaction ion equation: Al (OCH^) 3+3CH3OCH2CH2OH > Al(OCH2CH2OCH3)3+3CH3OH. This reaction was carried out with a

l6o% excess of CH^OC^C^OH. Instead of using an excess of CH3OCH2CH2OH, the theoretical amount can also be used, and the excess of this compound is replaced with another solvent, preferably benzene or toluene. The methyl alcohol that was formed was removed from the reaction mixture during the reaction by distillation using of a rectification column. After the methyl alcohol had been removed, the excess CH 2 OCF 2 CH 2 OH was removed under vacuum. The reaction product was a liquid, highly viscous compound of the formula A1(OCH0CH0OCH0)„ which is miscible with benzene,

v 2 23'j' toluene and ethers in any ratio.

Example 2

Into a 100 ml three-necked round bottom flask equipped with a stirrer, reflux condenser and dropper, 1.7 g of 85% Na^AlHg (the other 15% was aluminum and silicon) was charged, and 35 ml of tetrahydrofuran was added. The mixture was heated to boiling, and a solution of 8.26 g of Al[0CH2CH2N(CH3)2<]>3 in 15 ml of tetrahydrofuran was added dropwise with stirring. The whole was heated for a further 43 minutes and the mixture was then cooled to 15°C. After the filtration, the tetrahydrofuran was removed from the filtrate, and a residue was obtained which was dried at 100°C and a pressure of 0.1 mm Hg. 9.19 of a compound with the formula NaAlH2[OCH2CH2N(CH3)2]2 was obtained, which corresponded to 93.5% of the theoretical yield according to reaction equation 8. The compound (CHg^NCH^^OH which is necessary for the production of the compound Al[OCH2CH2N(CH3)2<]>3 was prepared by a reaction commonly known for the conversion of primary amines to tertiary amines by starting from H2NCH2CH20H, formaldehyde and formic acid. the starting compound A1[0CH2<C>H2N(CH3 )2]^ was prepared from aluminum methylate in the same way as described in example 1 in connection with the preparation of Al(0CH2CH20CH3)3.

Ex empe1 3

7.35 g of Na3AlH6 and 11.86 g of Al[OCH2CH2N(CH3)2]3 were placed in a 250 ml flask equipped with a reflux condenser, stirrer and dropping funnel, and 85 ml of tetrahydrofuran was added. The mixture was heated under reflux, and a solution of 2.72 g of AlCl3 in 25 ml of tetrahydrofuran were added dropwise over 30 minutes. The mixture was then heated for a further 45 minutes and then cooled to 20°C and filtered. The tetrahydrofuran was removed from the filtrate and the distillation residue was dried at 100°C and 0.1 mm Hg. 15.84 g of NaAlH3OCH2CH2N(CH3)2 were obtained, which corresponds to 91.5% of the theoretical yield.

Example 4

5.6 g (91.1%) Na3AlH£, 500 ml benzene and 26.1 g

was filled into a 1 liter three-necked flask fitted with a stirrer, water cooler and dropping funnel. The reaction mixture was refluxed and by the dropwise addition of a solution of 200 ml of benzene over 30 minutes, after which the reaction mixture was refluxed for a further 4 hours. The whole was then cooled to 15°C and filtered. The filter cake was washed with benzene, the benzene was removed from the combined filtrate and the distillation residue was dried at 100°C and 0.1 mm Hg. This gave 147.2 g, which constituted 97.6% of the theoretical yield. For the production of

the same procedures were used as

given in Example 4.

Example 5

5.6 g (91.1%) of Na^AlHg and 250 ml of benzene were charged in the same apparatus as used in example'4. The reaction mixture was refluxed and during the dropwise addition of a solution of 38.4 g of Al(OCH2CH2OCH2C<H>2OCH3)3 in 80 ml of benzene. The reaction mixture was treated as described in example 4 and gave 42 g of NaAlH2(OCH2CH2OCH2CH2OCH3)2, which corresponded to 96.56% of the theoretical yield.

The alcoholate Al(OCH2CH2OCH2<CH>2OCH3)3 was prepared from CH3CJH2CH2O<CH>2CH2OH by the method described in example 1.

Example 6

5.6 g (91.1%) Na3AlH6, 27.6 g Na[0(CH2)20(CH2)^OCH2CH3] and

600 ml of benzene was filled in the same apparatus as described in example 4 - A solution of 127.6 g was added dropwise to the reaction mixture during reflux distillation

Al[0(CH2)20(CH2)^O<CH>2CH3]3 in 250 ml of benzene during 45 min. After the same treatment of the reaction mixture as described in example 4, 154.0 g of NaAlH[0(CH2)20(CH2)^0CH20CH3]3 was obtained, which corresponded to 96.13% of the theoretical yield.

The alcohol with the formula C2H^O(CH2)^0(CH2)20H required for the production of the starting alcoholate was prepared from 1,4 butanediol by reaction of a hydroxyl group with sodium hydride in boiling toluene and subsequent alkylation with C^H^Br. The obtained product C^H^O^H^OH was converted to the alcoholate by reaction with sodium hydride in boiling toluene, and the alcoholate C2H^O(CH2)^ONa was then alkylated with ClCH2CH2OH, whereby C2H^O(CH2)^0( CH 2 ) 2 OH was obtained.

The starting alcoholate with the formula Al[0(CH2)20(CH2)^OC2H^]3 was prepared from aluminum methylate and C2H^0(CH2)^0(CH2)20H in the same way as described in example 4. The compound with the formula Na0(CH2)20 (CH2)^0C2H^ was prepared by reaction of sodium hydride with C2H^O(CH2)^0(CH2)2OH in the same way as in example 4.

Example 7

5.6 g (91.1%) of Na3AlH6 and 250 ml of tetrahydrofuran were filled in the same apparatus as described in example 4. The reaction mixture was boiled under reflux, and a solution of 22.3 g of Al[OC2H^N(C2<H >5)2]3 in 8u ml of tetrahydrofuran was added dropwise over 45 minutes.

After treatment of the reaction mixture in the same way as described in example 4, 26.719 NaAlH2[OC2H^N(C2H^)2]2 was obtained, which corresponded to 97.3% of the theoretical yield.

The starting alcoholate Al[OCH2CH2N(C2H^)2]^ was prepared from aluminum alcoholate and (C2H^)2NCH2CH2OH according to the method described in example 1.

Example 8

5.6 g of trisodium aluminum hexahydride with 91.1% purity and 250 ml of benzene were filled in the same apparatus as used in example 4-

The suspension was heated to boiling, and a solution of 37.2 g

in 80 ml of benzene was added dropwise over 30 minutes. By the same procedure as in example 4, 39.8 g were obtained, which corresponded to 94% of the theoretical. The starting material was prepared by reaction of aluminum methylate with a solution of in toluene and in a ratio of toluene to The compound was added in an amount of 150% beyond the theoretical. In accordance with equation 1, the methyl alcohol was removed from the reaction mixture in a rectification column. The toluene was removed at atmospheric pressure, and finally the excess was removed

removed using a partial vacuum and a temperature of up to 150°C. The product obtained was an undistillable, highly viscous substance which was miscible with benzene, toluene and ethers in any ratio,

in

Example 9

A suspension of 5.6 g of trisodium aluminum hexahydride with 91.1% purity in 250 ml of benzene was filled in the same apparatus as used in example 4- The suspension was reflux distilled by the simultaneous addition of a solution of 33.3 g of Al[OCH2CH2CH2N(CH3 )2]3in 80 ml of benzene during 30 minutes. The reaction product was further processed by the method described in example 4 and gave 36.7 g of NaAlH 2 [OCH 2 CH 2 N(CH 3 ) 2 ] 2 .

To prepare the starting material, the compound was first made

(CH2)2NCH2CH2CH2OH prepared from the compound HOCH2CH2CH2NH2 by the usual reaction with formaldehyde and formic acid. The compound Al[OCH2CH2CH2N(CH3)2<]>3 was then prepared from (CH3)2NCH2CH2CH2OH in the same manner as described in Example 8. The compound obtained was a highly viscous, undistillable liquid which was miscible with benzene, toluene and ethers in which preferably relationship.

Example IQ

A suspension of 5.6 g of trisodium aluminum hexahydride with 91.1% purity in 250 ml of benzene was filled in the same apparatus as used in example 4. The suspension was reflux distilled by simultaneous dropwise addition of a solution of 55.5 g of AlfOCH^^N ^H^F^OCH^jj in 8o ml of benzene during 30 minutes. In the same way as described in Example 4, 59.4 Q of NaAlH2[O<CH>2CH2N(CH2CH2OCH3)2]2 was obtained, which corresponded to 94.7% of the theoretical.

For the production of the starting material, (CH3OCH2CH2)2NCH2CH2OH first had to be prepared in accordance with the following reaction equations:

To a boiling suspension of sodium hydride in xylene during reflux distillation (200 ml of xylene per 1 gram molecule of sodium hydride) Na(CH2CH20H)3 was added dropwise with stirring, and the heating was continued until the evolution of hydrogen ceased. Then (CH 3 O ) 2 SO 2 was added under the same conditions, refluxing resumed and continued until hydrogen evolution ceased. The mixture was cooled and added 100 ml of a 60% solution of potassium hydroxide per gram molecule (CH3O)2S02. The reaction mixture was then filtered, the solid phase washed with xylene and the xylene solution HOCH2CH2N(CH2CH2OCH3)2 extracted with water, neutralized and slightly acidified with hydrochloric acid. The hydrogen chloride obtained was recovered by evaporation of the water under vacuum, and the base was liberated by the addition of a 70% solution of potassium hydroxide in water. A small surplus was used, but no more than 10% of the theoretical quantity.

The mixture was then stirred with diethyl ether, and the precipitated potassium chloride was filtered. The product (CH3OCH2CH2)2NCH2CH2OH was obtained by distilling the ether-containing solution and converted to aluminate in the same way as in example 8-

Example 11

A suspension of 5.6 g of Na^AlH^ with 91.1% purity in 250 ml of benzene was filled in the same apparatus as was used in example 4 - The suspension was boiled under reflux distillation, and a solution of 72.3 g Al[OCH2CH2N(CH2CH2CH2CH2OCH3)2]3 in 120 ml of benzene was added dropwise over 30 minutes. The reaction was carried out in the same way as in Example 4, and 72.1 g of NaAlH 2 [OCH 2 CH 2 N(CH 2 CH 2 CH 2 CH 2 OCH 3 ) 2 ] 2 was obtained, which corresponded to 93.2% of the theoretical.

The necessary amino alcohol used as starting material was prepared from HOCH2CH2NH2 by alkylation of CH30CH2CH2CH2CH2C1. The latter compound was prepared by methylation of a hydroxyl group in 1,4-butanediol and then converted to the chloride by means of thionyl chloride. The required compound [(CH3OCH2CH2CH2CH2)2NCH2CH2o]3Al was prepared in the same way as described in Example 1.

Example 12

A suspension of 5.6 g of trisodium aluminum hexahydride with 91.1% purity in 200 ml of tetrahydrofuran was prepared in the same apparatus as used in Example 4. Under the same conditions as in Example 4, a solution of 20.4 g (n-C .^O) 3A1 in 200 ml of tetrahydrofuran added. The preparation, which was carried out in the same way as in example 4, gave 24.1 g of NaAlH2[0(n-C3Hy)]2, which corresponded to 94.3% of the theoretical.

Example 13~15

Using the same apparatus as in example 4, compounds with the formula NaAlH2Q2 were prepared in accordance with the following reaction equation:

The radical Q for each example is reproduced in the following table 1.

A suspension of 5.6 g (0.05 mol) of trisodium aluminum hexahydride with 91.1% purity in 250 ml of benzene and 0.1 mol of AlQ3 in 100 ml of benzene was prepared in the apparatus described in example 4. Q thereby also had the different - meaning indicated in the following table. The reaction mixture was refluxed at normal pressure, and a solution of 1.1 mol AIQ^ in 100 ml benzene was added dropwise over 30 minutes. The reaction mixture was then refluxed for an additional 4 hours. After cooling to 15°C, the clear solution was filtered. The solid residue mainly contained the starting materials and impurities and was removed from the filtrate by washing with benzene. The benzene was distilled off from the resulting clear solution, and the combined product was dried in a vacuum of 0.1 mm Hg at 100°C.

The obtained yields are indicated in table 1 in grams and percentages in relation to the different reaction participants used in examples 13 - 15•

Claims (2)

1. Procedure for the production of complex, organically substituted sodium aluminum hydrides with the general formula: x 4 -x NaAlHZ, where x is 1, 2 or 3, and Z is a methoxy, ethoxy or propoxy group or a group Q derived by removal of active hydrogen from (1) tetrahydrofurfuryl-lower alkanols, (2) tetrahydropyranyl-lower alkanols, (3) ether alcohols of the formula: HO-(CH2 )n -OR', where R <*> is alkyl of 1-4 carbon atoms or alkaryl of 6-8 carbon atoms, and n is 2, 3 or 4, (4) polyether alcohols obtained by condensation of ether alcohols and diols during elimination of water, with the formula: HO(CH2 )z O(CH2 )w OR' where z and w, which are the same or different, are 2, 3 or 4, and R' is as indicated above, or (5) aminoalcohols of the general formula R2 N(CH2 )z OH, where z is 2, 3 or 4, and R an alkyl or alkoxy-alkyl group where the alkyl group contains 1-4 carbon atoms, by reacting a metal hydride with an aluminum trialcoholate at elevated temperature in the presence of an inert organic solvent, characterized in that trisodium aluminum hexahydride, Na^ AlHg, is reacted with a compound of the formula AlZ^ optionally in the presence of NaZ and/or AlCl^» where Z is as stated above. 2. Method according to claim 1, characterized in that a compound with the formula A1Z- is used, where Z is CH_OCH„CH„0-. 3 3 <Z 2 3- Method according to claim 1, characterized in that a compound with the formula AlZ^ is used where Z is (CH^ ^N-CI^CHgO-.