STABLE ALKALI AMIDE SOLUTIONS AND PROCESSES FOR PREPARING SAME

Abstract

The object of the invention are solutions of alkali metal amides MNR.sup.1R.sup.2, wherein M is an alkali metal selected from Li, Na, K, Rb, Cs; R.sup.1 and R.sup.2 independently of one another are linear, branched or cyclic alkyl groups having 1 to 8 C atoms or together are a cycloalkyl radical, the alkali metal amides being present in methyltetrahydropyran or in a solvent mixture containing methyltetrahydropyran, and processes for their preparation.

Claims

1. Solutions of alkali metal amides MNR.sup.1R.sup.2, wherein M is an alkali metal selected from Li, Na, K, Rb, Cs; R.sup.1 and R.sup.2 independently of one another are linear, branched or cyclic alkyl groups having 1 to 8 C atoms or together are a cycloalkyl radical, characterized in that the alkali metal amides are present in methyltetrahydropyran or in a solvent mixture containing methyltetrahydropyran.

2. Solutions according to claim 1, characterized in that M is preferably lithium, and R.sup.1 and R.sup.2 are isopropyl.

3. Solutions according to claim 1 or 2, characterized in that the solvent mixture contains, in addition to 4-methyltetrahydropyran, at least one hydrocarbon which is liquid at room temperature and the molar ratio between the alkali metal amide LDA and 4-methyltetrahydropyran is preferably between 1:0.5 and 1:3.

4. A method for the preparation of alkali metal amides MNR.sup.1R.sup.2, wherein M is an alkali metal selected from Li, Na, K, Rb, Cs; R.sup.1 and R.sup.2 independently of one another are linear, branched or cyclic alkyl groups having 1 to 8 C atoms or together are a cycloalkyl radical, characterized in that the preparation is carried out in methyltetrahydropyran or in a solvent mixture containing methyltetrahydropyran, the molar ratio between alkali metal amide and methyltetrahydropyran being at least 0.5:1, preferably at least 1:1.

5. The method according to claim 4, characterized in that R.sup.1 and R.sup.2 are selected from the group consisting of: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, octyl, decyl, 2-ethylhexyl, cyclopentyl, cyclohexyl, or as a common cycloalkyl radical having 3 to 12 C atoms.

6. The method according to claim 5, characterized in that the cyclic amine is 2,2,6,6-tetramethylpiperidide.

7. The method according to claims 4 to 6, characterized in that only methyltetrahydropyrans, preferably only 4-methyltetrahydropyran, are/is used as solvent.

8. The method according to claims 4 to 7, characterized in that mixtures of at least one methyltetrahydropyran and at least one liquid hydrocarbon are preferably used as solvent.

9. The method according to claims 4 to 8, characterized in that aliphatic, cycloaliphatic or aromatic compounds are used as the hydrocarbon, either alone or as a mixture.

10. The method according to claim 9, characterized in that the hydrocarbon used is at least one compound selected from the group consisting of pentanes, hexanes, heptanes, octanes, decanes, cyclohexane, methylcyclohexane, benzene, toluene, ethylbenzene, xylenes and/or cumene.

11. The method according to claims 4 to 10, characterized in that the alkali metal is used in powder form or as granules with grain sizes <100 μm or <10 mm, respectively.

12. The method according to claims 4 to 11, characterized in that the molar ratio between alkali metal and methyltetrahydropyran is 1:0.5 to 1:3.

13. The method according to claims 4 to 12, characterized in that at least one hydrogen acceptor A selected from the group consisting of α-aryl olefins or 1,3-diene having 4 to 12 C atoms is added during the synthesis reaction.

14. The method according to claim 13, characterized in that the hydrogen acceptor A is specifically selected from the group consisting of: styrene, α-methylstyrene, butadiene, isoprene or 1,3-cyclohexadiene.

15. The method according to claims 4 to 14, characterized in that the hydrogen acceptor is used in a molar ratio of 0.3 to 0.6:1, based on the amount of amine used, the reaction temperature being between 0 and 200° C., preferably 20 to 110° C.

Description

[0035] The invention is explained in more detail using an example and two figures.

[0036] FIG. 1 shows: The thermal behavior (Radex test) of a mixture of 0.09 g Li-powder and 1.8 g THF

[0037] FIG. 2 shows: The thermal behavior (Radex test) of a mixture of 0.09 g Li powder and 1.8 g 4-MTHP

EXAMPLE 1

[0038] Preparation of a 20% solution of lithium diisopropylamide (LDA) in 4-methyltetrahydropyrane/heptane/ethylbenzene

[0039] 107 g heptane (isomer mixture “Iparsol 7”, available from DHC GmbH), 79 g 4-MTHP (supplier Kuraray), 3.45 g lithium granulate (edge length about 3 mm, available from Albemarle) and 50.4 g diisopropylamine (supplier Merck) were placed in an inert, i.e. dry 500 ml glass reactor filled with the blanket gas argon and stirred for one hour at 25° C. Then it was heated up to 30° C. and 26.2 g styrene were added from a dropping funnel within three hours. During the addition, the mixture discolored slightly brownish.

[0040] After the end of dosing, the turbid reaction mixture was stirred for another 30 minutes and then filtered through a glass frit. The result was 251 g of a clear yellowish product solution. The active base concentration (thermometry method) was 1.82 mmol/g, resulting in an LDA concentration of 19.5 wt %.