4,6-DIFLUORODIBENZOFURAN DERIVATIVES

Abstract

4,6-difluorodibenzofuran derivatives of the formula I

##STR00001##

the preparation thereof, the use thereof as components in liquid-crystalline media and electro-optical display elements which contain the liquid-crystalline media.

Claims

1. A compound of formula I: ##STR00027## in which m and n one of m and n is 1 and the other of m and n is 0, and R.sup.1 and R.sup.2, independently of one another, denote an alkyl radical having 1 to 15 C atoms or an alkenyl or alkynyl radical having 2 to 15 C atoms, each of which are optionally mono- or polyhalogenated, with the proviso that the compound is not 3-butoxy-4,6-difluoro-7-n-propyldibenzofuran.

2. (canceled)

3. A compound according to claim 1, wherein R.sup.1 and R.sup.2, independently of one another, denote an alkyl radical having 1 to 7 carbon atoms or an alkenyl radical having 2 to 7 carbon atoms.

4. A compound according to claim 1, wherein the sum of the number of carbon atoms in R.sup.1 and R.sup.2 is 5, 6, 7, 8 or 9.

5. A compound according to claim 1, which is of formula IB ##STR00028## in which alkyl denotes an alkyl radical having 1 to 15 carbon atoms, and R.sup.2 has the meanings as defined for the compound of formula I.

6. A compound according to claim 1, which is one of the following compounds ##STR00029##

7. A compound according to claim 1, wherein R.sup.1 and R.sup.2, independently of one another, denote an alkyl radical having 2 to 6 carbon atoms or an alkenyl radical having 3 to 6 carbon atoms or CF.sub.3.

8. (canceled)

9. A compound according to claim 1, wherein m=0 and n=1.

10. A Liquid-crystalline medium comprising at least two compounds, one of which is a compound according to claim 1.

11. An electro-optical display element containing a liquid-crystalline medium according to claim 10.

12. A process for preparing a compound of formula I according to claim 1, comprising deprotonating a compound of formula (B) at position 3 ##STR00030## in which m and R.sup.1 independently are defined as for the compound of formula I according to claim 1, by a deprotonation reagent and converting into a compound of formula (C) ##STR00031## in which, independently, m, R.sup.1 are defined as for the compound of formula I, X denotes B(OR).sub.2, C(OH)R or OH, and R denotes an alkyl radical having 1 to 14 C atoms.

13. A compound according to claim 1, wherein one of R.sup.1 and R.sup.2 is methyl or ethyl.

14. A compound according to claim 1, which has a negative dielectric anisotropy .

15. A compound according to claim 1, which has a negative dielectric anisotropy of <8.

16. A compound according to claim 1, which is one of the following compounds ##STR00032## TABLE-US-00004 R.sup.1 R.sup.2 CH.sub.3 CH.sub.3 CH.sub.3 C.sub.2H.sub.5 CH.sub.3 C.sub.3H.sub.7 CH.sub.3 C.sub.4H.sub.9 CH.sub.3 C.sub.5H.sub.11 CH.sub.3 C.sub.6H.sub.13 C.sub.2H.sub.5 CH.sub.3 C.sub.2H.sub.5 C.sub.2H.sub.5 C.sub.2H.sub.5 C.sub.3H.sub.7 C.sub.2H.sub.5 C.sub.4H.sub.9 C.sub.2H.sub.5 CH.sub.2CH(CH.sub.3).sub.2 C.sub.2H.sub.5 (CH.sub.2).sub.2CHCH.sub.2 C.sub.2H.sub.5 (CH.sub.2).sub.2CH(CH.sub.3).sub.2 C.sub.2H.sub.5 C.sub.5H.sub.11 C.sub.2H.sub.5 C.sub.6H.sub.13 C.sub.2H.sub.5 (CH.sub.2).sub.3CH(CH.sub.3).sub.2 C.sub.3H.sub.7 CH.sub.3 C.sub.3H.sub.7 C.sub.2H.sub.5 C.sub.3H.sub.7 C.sub.3H.sub.7 C.sub.3H.sub.7 (CH.sub.2).sub.2CHCH.sub.2 C.sub.3H.sub.7 C.sub.5H.sub.11 C.sub.3H.sub.7 C.sub.6H.sub.13 C.sub.4H.sub.9 CH.sub.3 C.sub.4H.sub.9 C.sub.2H.sub.5 C.sub.4H.sub.9 C.sub.3H.sub.7 (CH.sub.2).sub.2CHCH.sub.2 C.sub.2H.sub.5 C.sub.4H.sub.9 C.sub.4H.sub.9 C.sub.4H.sub.9 C.sub.5H.sub.11 C.sub.4H.sub.9 (CH.sub.2).sub.2CHCHCH.sub.3*.sup.) C.sub.4H.sub.9 C.sub.6H.sub.13 C.sub.5H.sub.11 CH.sub.3 C.sub.5H.sub.11 C.sub.2H.sub.5 (CH.sub.2).sub.2CHCHCH.sub.3*.sup.) C.sub.2H.sub.5 C.sub.5H.sub.11 C.sub.3H.sub.7 C.sub.5H.sub.11 C.sub.4H.sub.9 C.sub.5H.sub.11 (CH.sub.2).sub.2CHCH.sub.2 C.sub.5H.sub.11 C.sub.6H.sub.13 *.sup.)trans isomer.

17. A compound according to claim 1, which is one of the following compounds ##STR00033## TABLE-US-00005 R.sup.1 R.sup.2 CH.sub.3 C.sub.2H.sub.5 CH.sub.3 C.sub.3H.sub.7 CH.sub.3 C.sub.4H.sub.9 CH.sub.3 C.sub.5H.sub.11 CH.sub.3 C.sub.6H.sub.13 C.sub.2H.sub.5 C.sub.2H.sub.5 C.sub.3H.sub.7 C.sub.2H.sub.5 C.sub.3H.sub.7 C.sub.3H.sub.7 C.sub.3H.sub.7 (CH.sub.2).sub.2CHCH.sub.2 C.sub.4H.sub.9 C.sub.2H.sub.5 (CH.sub.2).sub.2CHCH.sub.2 C.sub.2H.sub.5 C.sub.5H.sub.11 C.sub.2H.sub.5 (CH.sub.2).sub.2CHCHCH.sub.3*.sup.) C.sub.2H.sub.5 C.sub.5H.sub.11 C.sub.4H.sub.9 C.sub.5H.sub.11 (CH.sub.2).sub.2CHCH.sub.2 *.sup.)trans isomer.

18. A compound according to claim 1, wherein R.sup.1 and R.sup.2 independently of one another, denote an alkyl radical having 1 to 15 C atoms, each of which are optionally mono- or polyhalogenated.

19. A compound according to claim 1, wherein R.sup.1 and R.sup.2 independently of one another, denote an alkyl radical having 1 to 15 C atoms.

20. A compound according to claim 1, wherein R.sup.1 and R.sup.2 one of R.sup.1 and R.sup.2 denotes an alkyl radical having 1 to 15 C atoms and the other of R.sup.1 and R.sup.2 denotes an alkenyl or alkynyl radical having 2 to 15 C atoms, each of which are optionally mono- or polyhalogenated.

21. A compound according to claim 1, wherein R.sup.1 and R.sup.2 one of R.sup.1 and R.sup.2 denotes an alkyl radical having 1 to 15 C atoms and the other of R.sup.1 and R.sup.2 denotes an alkenyl or alkynyl radical having 2 to 15 C atoms.

Description

EXAMPLES

[0076] The starting substances can be obtained in accordance with generally accessible literature procedures or commercially.

Example 1: 3-Butoxy-4,6-difluoro-7-propoxydibenzofuran

[0077] ##STR00015##

Step 1

[0078] ##STR00016##

[0079] 50 g of dibenzofuran are initially introduced in 1500 ml of THF, and 152 g of 15% BuLi soln. in hexane are added dropwise at 60 to 75 C. The mixture is warmed to RT and stirred for a further 3 h. The mixture is then re-cooled to 75 C., and a solution of 112.5 g of N-fluorobenzenesulfonimide in 1000 ml of THF is added at 75 to 60 C. After a further 30 min at 70 C., the reaction mixture is allowed to warm to ambient temperature, and the batch is hydrolysed using water and subjected to extractive work-up.

[0080] The crude product (red-brown oil) is purified by chromatography (eluent: n-heptane).

[0081] White crystals.

Step 2

[0082] ##STR00017##

[0083] 40 g of 4-fluorodibenzofuran are initially introduced in 450 ml of THF, and 96 g of 15% BuLi soln. in hexane are added dropwise at 60 to 75 C. The mixture is stirred for a further 2 hours. A solution of 25 g of trimethyl borate in 80 ml of THF is then added at 75 to 60 C. After a further 30 min at 70 C., the reaction mixture is allowed to warm to ambient temperature, and the batch is slowly hydrolysed using a mixture of 30 g of glacial acetic acid and 40 ml of water. 40 g of 30% hydrogen peroxide are subsequently added dropwise at such a rate that the temperature does not exceed 45 C. The mixture is stirred at RT for a further 12 h and subjected to extractive work-up.

[0084] The crude product is purified by chromatography (eluent: n-heptane/MTB 4/1).

[0085] White crystals.

Step 3

[0086] ##STR00018##

[0087] 36.8 g of 4-fluorodibenzofuran-3-ol, 13.6 g of imidazole and 24.5 g of DMAP are dissolved in 700 ml of DMF, and a solution of 55 g of chlorotriisopropylsilane in 35 ml of DMF is added at 25 C. The mixture is stirred at RT for a further 12 h, and the batch is carefully poured into ice-water and subjected to extractive work-up.

[0088] The crude product is purified by chromatography (eluent: n-heptane/chlorobutane 9/1).

[0089] Colourless oil.

Step 4

[0090] ##STR00019##

[0091] 30.8 g of (4-fluorodibenzofuran-3-yloxy)triisopropylsilane are initially introduced in 850 ml of THF, and 106 g (3 eq.) of 15% BuLi soln. in hexane are added dropwise at 60 to 75 C. The mixture is warmed to 40 C. and stirred at this temperature for a further 5 h. The mixture is then re-cooled to 65 C., and a solution of 78.8 g of N-fluorobenzenesulfonimide in 300 ml of THF is added at 65 to 50 C. After a further 30 min at 50 C., the reaction mixture is allowed to warm to ambient temperature, and the batch is hydrolysed using water and subjected to extractive work-up.

[0092] The crude product (red-brown oil) is purified by chromatography (eluent: n-heptane/chlorobutane 4/1) and recrystallised from ethanol.

[0093] White crystals.

Step 5

[0094] ##STR00020##

[0095] 15.4 g of (4,6-difluorodibenzofuran-3-yloxy)triisopropylsilane are dissolved in 150 ml of THF, and 57 ml of a 1 M solution of tetrabutylammonium fluoride in THF are added at 5 C. The mixture is stirred at RT for a further 30 min and subjected to extractive work-up.

[0096] The crude product is purified by chromatography (eluent: n-heptane/MTB 2/1) and recrystallised from heptane/toluene 1/1.5.

[0097] White crystals.

Step 6

[0098] ##STR00021##

[0099] 17.3 g of 4,6-difluorodibenzofuran-3-ol are boiled under reflux with 14.5 g of n-propyl bromide and 16.3 g of potassium carbonate in 150 ml of methyl ethyl ketone for 15 h. The mixture is subjected to extractive work-up.

[0100] The crude product is purified by chromatography (eluent: n-heptane/MTB 4/1) and recrystallised from heptane.

[0101] White crystals.

Step 7

[0102] ##STR00022##

[0103] 17.3 g of 4,6-difluoro-3-propyloxydibenzofuran are initially introduced in 250 ml of THF, and 33 g of 15% BuLi soln. in hexane are added dropwise at 60 to 75 C. The mixture is stirred for a further 2 h. A solution of 7.9 g of trimethyl borate in 20 ml of THF is then added at 75 to 60 C. After a further 30 min at 70 C., the reaction mixture is allowed to warm to RT, and the batch is slowly hydrolysed using a mixture of 10 g of glacial acetic acid and 12 ml of water. 16 g of 30% hydrogen peroxide are subsequently added dropwise at such a rate that the temperature does not exceed 45 C. The mixture is stirred at RT for a further 12 h and subjected to extractive work-up.

[0104] The crude product is purified by chromatography (eluent: n-heptane/MTB 3/1).

[0105] Yield 9.9 g. White crystals.

Step 8

[0106] ##STR00023##

[0107] 7.1 g of 4,6-difluoro-7-propoxydibenzofuran-3-ol are boiled under reflux with 7 g of n-butyl bromide and 5.3 g of potassium carbonate in 65 ml of methyl ethyl ketone for 5 h. The mixture is subjected to extractive work-up. The crude product is purified by chromatography (eluent: n-heptane/chlorobutane 2/1) and recrystallised from heptane.

[0108] Yield 7.9 g. White crystals.

[0109] Phases: C 68 I (m.p. 68 C., cf. also table).

[0110] The following compounds are prepared analogously to Example 1:

##STR00024##

[0111] The radicals R.sup.1/2 are straight-chain, i.e. unbranched, unless indicated otherwise. The substance data are given in Table 1.

TABLE-US-00001 TABLE 1 .sub.1 CI.p. R.sup.1 R.sup.2 M.p. [ C.] n [mPa .Math. s] [ C.] CH.sub.3 CH.sub.3 CH.sub.3 C.sub.2H.sub.5 119 CH.sub.3 C.sub.3H.sub.7 93 15 0.193 149 59 CH.sub.3 C.sub.4H.sub.9 79 13 0.191 144 60 CH.sub.3 C.sub.5H.sub.11 79 14 0.185 144 46 CH.sub.3 C.sub.6H.sub.13 C.sub.2H.sub.5 C.sub.2H.sub.5 C.sub.2H.sub.5 C.sub.3H.sub.7 85 15 0.189 128 66 C.sub.2H.sub.5 C.sub.4H.sub.9 77 14 0.189 116 62 C.sub.2H.sub.5 CH.sub.2CH(CH.sub.3).sub.2 90 14 0.183 152 55 C.sub.2H.sub.5 (CH.sub.2).sub.2CHCH.sub.2 87 14 0.196 102 51 C.sub.2H.sub.5 (CH.sub.2).sub.2CH(CH.sub.3).sub.2 90 14 0.179 108 41 C.sub.2H.sub.5 C.sub.5H.sub.11 57 14 0.181 119 59 C.sub.2H.sub.5 C.sub.6H.sub.13 68 13 0.180 131 61 C.sub.2H.sub.5 (CH.sub.2).sub.3CH(CH.sub.3).sub.2 56 13 0.167 144 51 C.sub.3H.sub.7 C.sub.3H.sub.7 75 14 0.193 123 68 C.sub.3H.sub.7 C.sub.4H.sub.9 68 13 0.192 115 63 C.sub.3H.sub.7 C.sub.5H.sub.11 63 13 0.176 104 58 C.sub.3H.sub.7 C.sub.6H.sub.13 69 13 0.171 125 61 C.sub.4H.sub.9 C.sub.4H.sub.9 87 12 0.184 73 62 C.sub.4H.sub.9 C.sub.5H.sub.11 76 12 0.181 111 59 C.sub.4H.sub.9 (CH.sub.2).sub.2CHCHCH.sub.3*.sup.) 65 13 0.187 116 36 C.sub.4H.sub.9 C.sub.6H.sub.13 C.sub.5H.sub.11 CF.sub.3 64 4 0.132 73 24 C.sub.5H.sub.11 C.sub.5H.sub.11 C.sub.5H.sub.11 C.sub.6H.sub.13 *.sup.)trans isomer

[0112] The following compounds are prepared analogously to Example 1 and Scheme 2:

##STR00025##

[0113] The radicals R.sup.1/2 are straight-chain, i.e. unbranched, unless indicated otherwise. The substance data are given in Table 2.

TABLE-US-00002 TABLE 2 M.p. .sub.1 CI.p. R.sup.1 R.sup.2 [ C.] n [mPa .Math. s] [ C.] CH.sub.3 CH.sub.3 CH.sub.3 C.sub.2H.sub.5 100 10 0.197 75 45 CH.sub.3 C.sub.3H.sub.7 102 10 0.187 90 39 CH.sub.3 C.sub.4H.sub.9 82 9 0.183 84 35 CH.sub.3 C.sub.5H.sub.11 74 9 0.172 89 28 CH.sub.3 C.sub.6H.sub.13 61 9 0.170 98 26 C.sub.2H.sub.5 CH.sub.3 C.sub.2H.sub.5 C.sub.2H.sub.5 60 9 0.182 65 16 C.sub.2H.sub.5 C.sub.3H.sub.7 C.sub.2H.sub.5 C.sub.4H.sub.9 C.sub.2H.sub.5 CH.sub.2CH(CH.sub.3).sub.2 C.sub.2H.sub.5 (CH.sub.2).sub.2CHCH.sub.2 C.sub.2H.sub.5 (CH.sub.2).sub.2CH(CH.sub.3).sub.2 C.sub.2H.sub.5 C.sub.5H.sub.11 C.sub.2H.sub.5 C.sub.6H.sub.13 C.sub.2H.sub.5 (CH.sub.2).sub.3CH(CH.sub.3).sub.2 C.sub.3H.sub.7 CH.sub.3 C.sub.3H.sub.7 C.sub.2H.sub.5 63 10 0.177 74 9 C.sub.3H.sub.7 C.sub.3H.sub.7 54 8 0.174 72 7 C.sub.3H.sub.7 C.sub.4H.sub.9 65 8 0.167 67 8 C.sub.3H.sub.7 (CH.sub.2).sub.2CHCH.sub.2 50 8 0.171 55 6 C.sub.3H.sub.7 C.sub.5H.sub.11 C.sub.3H.sub.7 C.sub.6H.sub.13 C.sub.4H.sub.9 CH.sub.3 C.sub.4H.sub.9 C.sub.2H.sub.5 56 9 0.172 83 5 C.sub.4H.sub.9 C.sub.3H.sub.7 (CH.sub.2).sub.2CHCH.sub.2 C.sub.2H.sub.5 68 9 0.188 79 17 C.sub.4H.sub.9 C.sub.4H.sub.9 C.sub.4H.sub.9 C.sub.5H.sub.11 C.sub.4H.sub.9 (CH.sub.2).sub.2CHCHCH.sub.3*.sup.) C.sub.4H.sub.9 C.sub.6H.sub.13 C.sub.5H.sub.11 CH.sub.3 C.sub.5H.sub.11 C.sub.2H.sub.5 60 9 0.177 88 13 (CH.sub.2).sub.2CHCHCH.sub.3*.sup.) C.sub.2H.sub.5 90 10 0.193 94 49 C.sub.5H.sub.11 C.sub.3H.sub.7 C.sub.5H.sub.11 C.sub.4H.sub.9 64 8 0.162 73 11 C.sub.5H.sub.11 (CH.sub.2).sub.2CHCH.sub.2 70 8 0.165 71 2 C.sub.5H.sub.11 C.sub.6H.sub.13 *.sup.)trans isomer

[0114] The following compounds are prepared analogously to Example 1 and Scheme 3:

##STR00026##

[0115] The radicals R.sup.1/2 are straight-chain, i.e. unbranched, unless indicated otherwise. The substance data are given in Table 3.

TABLE-US-00003 TABLE 3 M.p. .sub.1 CI.p. R.sup.1 R.sup.2 [ C.] n [mPa .Math. s] [ C.] CH.sub.3 CH.sub.3 CH.sub.3 C.sub.2H.sub.5 CH.sub.3 C.sub.3H.sub.7 CH.sub.3 C.sub.4H.sub.9 CH.sub.3 C.sub.5H.sub.11 63 5 0.151 59 20 CH.sub.3 C.sub.6H.sub.13 CH.sub.3 (CH.sub.2).sub.2CHCH.sub.2 51 4 0.157 108 12 CH.sub.3 (CH.sub.2).sub.2CHCHCH.sub.3*.sup.) 59 5 0.181 100 10 C.sub.2H.sub.5 C.sub.2H.sub.5 C.sub.2H.sub.5 C.sub.3H.sub.7 42 4 0.142 33 57 C.sub.2H.sub.5 C.sub.4H.sub.9 C.sub.2H.sub.5 CH.sub.2CH(CH.sub.3).sub.2 C.sub.2H.sub.5 (CH.sub.2).sub.2CHCH.sub.2 C.sub.2H.sub.5 (CH.sub.2).sub.2CH(CH.sub.3).sub.2 C.sub.2H.sub.5 C.sub.5H.sub.11 C.sub.2H.sub.5 C.sub.6H.sub.13 C.sub.2H.sub.5 (CH.sub.2).sub.3CH(CH.sub.3).sub.2 C.sub.3H.sub.7 C.sub.3H.sub.7 C.sub.3H.sub.7 C.sub.4H.sub.9 C.sub.3H.sub.7 (CH.sub.2).sub.2CHCH.sub.2 50 4 0.151 44 49 C.sub.3H.sub.7 C.sub.5H.sub.11 C.sub.3H.sub.7 C.sub.6H.sub.13 C.sub.4H.sub.9 C.sub.4H.sub.9 38 5 0.131 44 63 (CH.sub.2).sub.2CHCH.sub.2 (CH.sub.2).sub.2CHCH.sub.2 60 5 0.159 51 36 C.sub.4H.sub.9 C.sub.5H.sub.11 C.sub.4H.sub.9 (CH.sub.2).sub.2CHCHCH.sub.3*.sup.) C.sub.4H.sub.9 C.sub.6H.sub.13 C.sub.5H.sub.11 (CH.sub.2).sub.2CHCH.sub.2 35 4 0.143 47 41 C.sub.5H.sub.11 C.sub.6H.sub.13 *.sup.)trans isomer

[0116] The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

[0117] From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.