METHOD FOR PRODUCING BIPHENYLAMINES FROM AZOBENZENES BY RUTHENIUM CATALYSIS

Abstract

The present invention relates to a novel method for preparing substituted biphenylamines

Claims

1. Method for preparing a biphenylamine of formula (I) ##STR00024## in which R.sup.1 is hydrogen, hydroxyl, fluorine, chlorine, C.sub.1-C.sub.4-alkyl, C.sub.1-C.sub.4-alkoxy, C.sub.1-C.sub.4-alkylthio or C.sub.1-C.sub.4-haloalkyl, X.sup.1 is hydrogen, alkoxy, alkanoyl, alkyl carboxylate, fluorine or chlorine, X.sup.2 is hydrogen, alkoxy, alkanoyl, alkyl carboxylate, fluorine or chlorine, X.sup.3 is hydrogen, alkoxy, alkanoyl, alkyl carboxylate, fluorine or chlorine, comprising: (I) reacting one or more azobenzenes of formula (II) ##STR00025## in which R.sup.1 is as defined above, with an aromatic compound of formula (III) ##STR00026## in which X.sup.1, X.sup.2 and X.sup.3 are each as defined above, and Hal is iodine, bromine or chlorine in the presence of a catalyst system consisting of a ruthenium catalyst, an activator, and a base, and (2) the azobenzenes of the formula (IV) thus obtained ##STR00027## in which IV, X.sup.1, X.sup.2 and X.sup.3 are as defined above, are hydrogenated to give the biphenylamines of the formula (I).

2. Method according to claim 1, wherein the solvent comprises ketones, nitriles, ethers, hydrocarbons and halogenated hydrocarbons and branched alcohols and/or a mixtures thereof.

3. Method according to claim 1, wherein the solvent comprises 1,4-dioxane, toluene, ortho-xylene, meta-xylene, para-xylene and/or a mixtures thereof.

4. Method according to claim 1, wherein the catalyst is [{RuCl.sub.2(p-cymene)}.sub.2].

5. Method according to claim 1, wherein the activator is an acid, optionally a carboxylic acid.

6. Method according to claim 1, wherein the activator is a carboxylic acid selected from the group consisting of: formic acid, acetic acid, propionic acid, pivalic acid, benzoic acid, 2-methylbenzoic acid, 3-methylbenzoic acid, 4-methylbenzoic acid, 2,3-dimethylbenzoic acid, 2,4-dimethylbenzoic acid, 2,5-dimethylbenzoic acid, 2,6-dimethylbenzoic acid, 3,4-dimethylbenzoic acid, 3,5-dimethylbenzoic acid, 2,4,6-trimethylbenzoic acid, 2,3,4-trimethylbenzoic acid, 3,4,5-trimethylbenzoic acid, 2,3,5-trimethylbenzoic acid, 2,3,6-trimethylbenzoic acid, phenylacetic acid, 2-methylphenylacetic acid, 3-methylphenylacetic acid, 4-methylphenylacetic acid, 2,5-dimethylphenylacetic acid, 2,3,6-trimethylphenylacetic acid, 2,3,5,6-tetramethylphenylacetic acid, 2,3,4,6-tetramethylphenylacetic acid, 2-chlorophenylacetic acid, 3-chlorophenylacetic acid, 4-chlorophenylacetic acid and 2,4-dichlorophenylacetic acid.

7. Method according to claim 1, wherein the activator is 2,4,6-trimethylbenzoic acid.

8. Method according to claim 1, wherein the base is an inorganic base.

9. Method according to claim 1, wherein the base is selected from the group consisting of: lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, lithium hydrogen carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, calcium carbonate and magnesium carbonate.

10. Method according to claim 1, wherein the base is potassium carbonate.

11. Method according to claim 1, wherein the activator is used in an amounts of 0.1 to 100 mole percent, based on the aromatic compound of the formula (III).

12. Method according to claim 1, wherein the ruthenium catalyst is used in amounts of 1 to 20 mole percent, based on the aromatic compound of the formula (III).

13. Method according to claim 1, wherein the molar ratio of azobenzene of the formula (II) to haloaromatic compound of the formula (III) is 1:0.4 to 1.

14. Method according to claim 1, wherein the molar ratio of azobenzene of the formula (II) to haloaromatic compound of the formula (III) is 1:0.45 to 0.9.

15. Method according to claim 1, wherein the solvent is 1,4-dioxane, the activator is 2,4,6-trimethylbenzoic acid, the aromatic compound of the formula (III) is a brominated aromatic compound, the base is potassium carbonate and the catalyst is [{RuCl.sub.2(p-cymene)}.sub.2].

Description

PREPARATION EXAMPLES

Example 1

Methyl 4′-methyl-2′-[(E)-(3-methylphenyl)diazenyl]biphenyl-4-carboxylate

[0073] ##STR00007##

[0074] In an oven-dried reaction vessel, a suspension consisting of (E)-bis(3-methylphenyl)diazene (210 mg, 1.0 mmol), [{RuCl.sub.2(p-cymene)}.sub.2] (15.3 mg, 5.0 mol %), MesCO.sub.2H (24.6 mg, 30 mol %), K.sub.2CO.sub.3 (138 mg, 1.0 mmol) and methyl 4-bromobenzoate (108 mg, 0.5 mmol) was stirred in dry 1,4-dioxane (2.0 ml) at 120° C. for 18 h in a nitrogen atmosphere. The reaction mixture was then diluted at room temperature with dichloromethane (DCM) (75 ml) and filtered through Celite and silica gel, and the filtrate was concentrated. The crude product thus obtained was purified by chromatography on silica gel (n-hexane/DCM: 7/3). 150 mg of methyl 4′-methyl-2′-[(E)-(3-methylphenyl)diazenyl]biphenyl-4-carboxylate were obtained as an orange solid (87% of theory).

[0075] M.p.=136-137° C. .sup.1H-NMR (CDCl.sub.3, 300 MHz): δ=8.10 (d, J=8.0 Hz, 2H), 7.64 (s, 1H), 7.60-7.53 (m, 4H), 7.49 (d, J=7.8 Hz, 1H), 7.40-7.32 (m, 2H), 7.30-7.24 (m, 1H), 3.96 (s, 3H), 2.48 (s, 3H), 2.42 (s, 3H). .sup.13C-NMR (CDCl.sub.3, 126 MHz): δ=167.0 (Cq), 152.7 (Cq), 149.3 (Cq), 143.6 (Cq), 138.8 (Cq), 138.7 (Cq), 137.1 (Cq), 131.7 (CH), 131.5 (CH), 130.7 (CH), 130.4 (CH), 128.8 (CH), 128.7 (CH), 128.5 (Cq), 124.2 (CH), 119.8 (CH), 116.1 (CH), 52.1 (CH.sub.3), 21.4 (CH.sub.3), 21.3 (CH.sub.3). IR (neat): 3030, 2951, 2914, 2850, 1721, 1606, 1438, 1279, 1106, 829, 790, 704, 533, 475, 436 cm-1. MS (El) m/z (relative intensity): 344 ([M+] 60), 329 (80), 285 (38), 225 (43), 165 (87), 91 (100), 65 (25), 43 (22). HR-MS (EI) m/z calculated for C.sub.22H.sub.20N.sub.2O.sub.2 [M+] 344.1525, found 344.1511.

Example 2

Methyl 4′-methyl-2′-[(E)-(3-methylphenyl)diazenyl]biphenyl-4-carboxylate

[0076] The experiment was carried out as described for Example 1, with the difference that toluene was used as solvent in place of 1,4-dioxane. The yield was 83% of theory.

Example 3

Methyl 4′-methyl-2′-[(E)-(3-methylphenyl)diazenyl]biphenyl-4-carboxylate

[0077] The experiment was carried out as described for Example 1, with the difference that ortho-xylene was used as solvent in place of 1,4-dioxane. The yield was 84% of theory.

Example 4

Methyl 4′-methyl-2′-[(E)-(3-methylphenyl)diazenyl]biphenyl-4-carboxylate

[0078] The experiment was carried out as described for Example 1, with the difference that tertiary amyl alcohol was used as solvent in place of 1,4-dioxane. The yield was 75% of theory.

Example 5

Methyl 4′-methyl-2′-[(E)-(3-methylphenyl)diazenyl]biphenyl-4-carboxylate

[0079] The experiment was carried out as described for Example 1, with the difference that sodium carbonate was used as base in place of potassium carbonate. The yield was 75% of theory.

Example 6

Methyl 4′-methyl-2′-[(E)-(3-methylphenyl)diazenyl]biphenyl-4-carboxylate

[0080] The experiment was carried out as described for Example 1, with the difference that potassium acetate was used as additive in place of MesCO.sub.2H. The yield was 79% of theory.

Example 7

Methyl 4′-methyl-2′-[(E)-(3-methylphenyl)diazenyl]biphenyl-4-carboxylate

[0081] The experiment was carried out as described for Example 1, with the difference that pivalic acid was used as additive in place of MesCO.sub.2H. The yield was 76% of theory.

Example 8

1-{4′-Methyl-2′-[(E)-(3-methylphenyl)diazenyl]biphenyl-4-yl}ethanone

[0082] ##STR00008##

[0083] In an oven-dried reaction vessel, a suspension consisting of (E)-1,2-di-m-tolyldiazene (210 mg, 1.0 mmol), [{RuCl.sub.2(p-cymene)}.sub.2] (15.3 mg, 5.0 mol %), MesCO2H (24.6 mg, 30 mol %), K.sub.2CO.sub.3 (138 mg, 1.0 mmol) and 4-bromoacetophenone (99.5 mg, 0.5 mmol) was stirred in dry 1,4-dioxane (2.0 ml) at 120° C. for 18 h in a nitrogen atmosphere. The reaction mixture was then diluted at room temperature with dichloromethane (DCM) (75 ml) and filtered through Celite and silica gel, and the filtrate was concentrated. The crude product thus obtained was purified by chromatography on silica gel (n-hexane/DCM: 7/3). 106 mg of 1-{4′-methyl-2′-[(E)-(3-methylphenyl)diazenyl]biphenyl-4-yl}ethanone were otained (65% of theory).

[0084] M.p.=123-124° C. .sup.1H-NMR (CDCl.sub.3, 300 MHz): 6=8.00 (d, J=8.6 Hz, 2H), 7.64-7.50 (m, 5H), 7.46 (d, J=7.8 Hz, 1H), 7.39-7.29 (m, 2H), 7.28-7.21 (m, 1H), 2.64 (s, 3H), 2.47 (s, 3H), 2.40 (s, 3H). .sup.13C-NMR (CDCl.sub.3, 126 MHz): δ=198.1 (C.sub.q), 152.9 (C.sub.q), 149.6 (C.sub.q), 144.0 (C.sub.q), 139.0 (C.sub.q), 138.9 (C.sub.q), 137.2 (C.sub.q), 135.6 (C.sub.q), 131.9 (CH), 131.7 (CH), 131.0 (CH), 130.5 (CH), 129.0 (CH), 127.6 (CH), 124.4 (CH), 119.9 (CH), 116.3 (CH), 26.5 (CH.sub.3), 21.2 (CH.sub.3), 21.1 (CH.sub.3). IR (neat): 2914, 2856, 2723, 1679, 1600, 1266, 819, 797, 688, 599 cm.sup.−1. MS (EI) m/z (relative intensity): 328 ([M.sup.+] 100), 285 (44), 209 (25), 165 (41), 91 (83), 65 (19), 65 (20), 43 (76). HR-MS (EI) m/z calculated for C.sub.22H.sub.20N.sub.2O [M.sup.+] 328.1576, found 328.1572.

Example 9

1-{4′-Methoxy-2′-[(E)-(3-methoxyphenyl)diazenyl]biphenyl-4-yl}ethanone

[0085] ##STR00009##

[0086] In an oven-dried reaction vessel, a suspension consisting of (E)-bis(3-methoxyphenyl)diazene (242 mg, 1.0 mmol), [{RuCl.sub.2(p-cymene)}.sub.2] (15.3 mg, 5.0 mol %), MesCO.sub.2H (24.6 mg, 30 mol %), K.sub.2CO.sub.3 (138 mg, 1.0 mmol) and 4-bromoacetophenone (99.5 mg, 0.5 mmol) was stirred in dry 1,4-dioxane (2.0 ml) at 120° C. for 18 h in a nitrogen atmosphere. The reaction mixture was then diluted at room temperature with dichloromethane (DCM) (75 ml) and filtered through Celite and silica gel, and the filtrate was concentrated. The crude product thus obtained was purified by chromatography on silica gel (n-hexane/DCM: 7/3). 96 mg of 1-{4′-methoxy-2′-[(E)-(3-methoxyphenyl)diazenyl]biphenyl-4-yl}ethanone were obtained (53% of theory).

[0087] M.p.=155-156° C. .sup.1H-NMR (CDCl.sub.3, 300 MHz): δ=7.98 (d, J=8.5 Hz, 2H), 7.61-7.22 (m, 7H), 7.13 (dd, J=8.6, 2.7 Hz, 1H), 7.00 (ddd, J=8.0, 2.7, 1.2 Hz, 1H), 3.91 (s, 3H), 3.78 (s, 3H), 2.63 (s, 3H). .sup.13C-NMR (CDCl.sub.3, 126 MHz): δ=198.1 (C.sub.q), 160.4 (C.sub.q), 160.2 (C.sub.q), 154.0 (C.sub.q), 150.2 (C.sub.q), 143.8 (C.sub.q), 135.4 (C.sub.q), 133.4 (C.sub.q), 131.6 (CH), 131.1 (CH), 129.9 (CH), 127.6 (CH), 118.5 (CH), 118.0 (CH), 117.4 (CH), 106.4 (CH), 99.4 (CH), 55.6 (CH.sub.3), 55.3 (CH.sub.3), 26.6 (CH.sub.3). IR (neat): 3068, 3005, 2961, 2940, 2915, 2834, 1673, 1604, 1513, 1269, 1132, 1040, 887, 819, 782, 634 cm.sup.−1. MS (EI) m/z (relative intensity): 360 ([M.sup.+] 100), 317 (57), 139 (38), 107 (53), 92 (24), 77 (30), 43 (54). HR-MS (EI) m/z calculated for C.sub.22H.sub.20N.sub.2O.sub.3 [M.sup.+] 360.1474, found 360.1466.

Example 10

1-{3′-Methyl-2′-[(E)-(2-methylphenyl)diazenyl]biphenyl-4-yl}ethanone

[0088] ##STR00010##

[0089] In an oven-dried reaction vessel, a suspension consisting of (E)-bis(2-methylphenyl)diazene (210 mg, 1.0 mmol), [{RuCl.sub.2(p-cymene)}.sub.2] (15.3 mg, 5.0 mol %), MesCO2H (24.6 mg, 30 mol %), K.sub.2CO.sub.3 (138 mg, 1.0 mmol) and 4-bromoacetophenone (99.5 mg, 0.5 mmol) was stirred in dry 1,4-dioxane (2.0 ml) at 120° C. for 18 h in a nitrogen atmosphere. The reaction mixture was then diluted at room temperature with dichloromethane (DCM) (75 ml) and filtered through Celite and silica gel, and the filtrate was concentrated. The crude product thus obtained was purified by chromatography on silica gel (n-hexane/DCM: 7/3). 87 mg of 1-{3′-methyl-2′-[(E)-(2-methylphenyl)diazenyl]biphenyl-4-yl}ethanone were obtained (53% of theory).

[0090] M.p.=125-126° C. (CDCl.sub.3, 300 MHz): δ=7.89 (d, J=8.6 Hz, 2H), 7.38-7.20 (m, 9H), 2.59 (s, 3H), 2.46 (s, 3H), 2.27 (s, 3H). .sup.13C-NMR (CDCl.sub.3, 126 MHz): 6=198.0 (C.sub.q), 151.0 (C.sub.q), 150.8 (C.sub.q), 145.7 (C.sub.q), 138.5 (C.sub.q), 135.2 (C.sub.q), 134.7 (C.sub.q), 131.5 (CH), 131.4 (CH), 131.3 (CH), 130.9 (C.sub.q), 130.4 (CH), 128.9 (CH), 128.2 (CH), 128.0 (CH), 126.4 (CH), 115.0 (CH), 26.5 (CH.sub.3), 19.1 (CH.sub.3), 17.0 (CH.sub.3). IR (neat): 3054, 2961, 2923, 1679, 1603, 1356, 1264, 955, 766, 600 cm.sup.−1. MS (El) m/z (relative intensity): 328 ([M.sup.+] 100), 285 (32), 209 (25), 165 (45), 91 (98), 65 (27), 43 (90). HR-MS (EI) m/z calculated for C.sub.22H.sub.20N.sub.2O [M.sup.+] 328.1576, found 328.1569.

Example 11

Ethyl 4′-methyl-2′-[(E)-(3-methylphenyl)diazenyl]biphenyl-4-carboxylate

[0091] ##STR00011##

[0092] In an oven-dried reaction vessel, a suspension consisting of (E)-bis(3-methylphenyl)diazene (210 mg, 1.0 mmol), [{RuCl.sub.2(p-cymene)}.sub.2] (15.3 mg, 5.0 mol %), MesCO.sub.2H (24.6 mg, 30 mol %), K.sub.2CO.sub.3 (138 mg, 1.0 mmol) and ethyl 4-bromobenzoate (107 mg, 0.5 mmol) was stirred in dry 1,4-dioxane (2.0 ml) at 120° C. for 18 h in a nitrogen atmosphere. The reaction mixture was then diluted at room temperature with dichloromethane (DCM) (75 ml) and filtered through Celite and silica gel, and the filtrate was concentrated. The crude product thus obtained was purified by chromatography on silica gel (n-hexane/DCM: 7/3). 113 mg of ethyl 4′-methyl-2′-[(E)-(3-methylphenyl)diazenyl]biphenyl-4-carboxylate were obtained (63% of theory).

[0093] M.p.=94-95° C. .sup.1H-NMR (CDCl.sub.3, 300 MHz): δ=8.09 (d, J=8.5 Hz, 2H), 7.63-7.60 (m, 1H), 7.58-7.50 (m, 4H), 7.47 (d, J=7.9 Hz, 1H), 7.39-7.30 (m, 2H), 7.28-7.22 (m, 1H), 4.41 (q, J=7.1 Hz, 2H), 2.47 (s, 3H), 2.41 (s, 3H), 1.41 (t, J=7.1 Hz, 3H). .sup.13C-NMR (CDCl.sub.3, 126 MHz): 8 =166.8 (C.sub.q), 153.0 (C.sub.q), 149.6 (C.sub.q), 143.7 (C.sub.q), 139.0 (C.sub.q), 138.9 (C.sub.q), 137.4 (C.sub.q), 131.9 (CH), 131.7 (CH), 130.8 (CH), 130.6 (CH), 129.0 (C.sub.q), 128.9 (CH), 128.8 (CH), 124.4 (CH), 119.9 (CH), 116.3 (CH), 60.9 (CH.sub.2), 21.3 (CH.sub.3), 21.1 (CH.sub.3), 14.3 (CH.sub.3). IR (neat): 2979, 2921, 2867, 1713, 1607, 1268, 1180, 1100, 775, 688 cm.sup.−1. MS (EI) m/z (relative intensity): 358 ([M.sup.+]47), 329 (100), 285 (37), 239 (19), 211 (17), 165 (60), 91 (80), 65 (14). HR-MS (EI) m/z calculated for C.sub.23H.sub.22N.sub.2O.sub.2 [M.sup.+] 358.1681, found 358.1669.

Example 12

(E)-1-(4′-Methoxy-4-methylbiphenyl-2-yl)-2-(3-methylphenyl)diazene

[0094] ##STR00012##

[0095] In an oven-dried reaction vessel, a suspension consisting of (E)-bis(3-methylphenyl)diazene (210 mg, 1.0 mmol), [{RuCl.sub.2(p-cymene)}.sub.2] (15.3 mg, 5.0 mol %), MesCO2H (24.6 mg, 30 mol %), K.sub.2CO.sub.3 (138 mg, 1.0 mmol) and 4-bromoanisole (93.5 mg, 0.5 mmol) was stirred in dry 1,4-dioxane (2.0 ml) at 120° C. for 18 h in a nitrogen atmosphere. The reaction mixture was then diluted at room temperature with dichloromethane (DCM) (75 ml) and filtered through Celite and silica gel, and the filtrate was concentrated. The crude product thus obtained was purified by chromatography on silica gel (n-hexane/DCM: 7/3). 106 mg of (E)-1-(4′-methoxy-4-methylbiphenyl-2-yl)-2-(3-methylphenyl)diazene were obtained (67% of theory).

[0096] M.p.=121-122° C. .sup.1H-NMR (CDCl.sub.3, 300 MHz): δ=7.69-7.59 (m, 2H), 7.55-7.52 (m, 1H), 7.47 (d, J=7.8 Hz, 1H), 7.43-7.31 (m, 4H), 7.29-7.23 (m, 1H), 6.97 (d, J=8.9 Hz, 2H), 3.87 (s, 3H), 2.46 (s, 3H), 2.43 (s, 3H). .sup.13C-NMR (CDCl.sub.3, 126 MHz): δ=158.8 (C.sub.q), 152.9 (C.sub.q), 149.4 (C.sub.q), 138.8 (C.sub.q), 137.7 (C.sub.q), 137.3 (C.sub.q), 131.9 (CH), 131.5 (CH), 131.4 (CH), 131.1 (C.sub.q), 130.4 (CH), 128.7 (CH), 124.0 (CH), 120.0 (CH), 116.0 (CH), 113.0 (CH), 55.3 (CH.sub.3), 21.4 (CH.sub.3), 21.2 (CH.sub.3). IR (neat): 2962, 2914, 2856, 1606, 1518, 1249, 1177, 1016, 816, 791, 689, 538 cm.sup.−1. MS (EI) m/z (relative intensity): 316 ([M.sup.+]100), 301 (40), 197 (67), 182 (65), 153 (42), 91 (78), 65 (30). HR-MS (EI) m/z calculated for C.sub.2H.sub.20N.sub.2O [M.sup.+] 316.1576, found 316.1577.

Example 13

(E)-1-(Biphenyl-2-yl)-2-phenyldiazene

[0097] ##STR00013##

[0098] In an oven-dried reaction vessel, a suspension consisting of (E)-1,2-diphenyldiazene (182 mg, 1.0 mmol), [{RuCl.sub.2(p-cymene)}.sub.2] (15.3 mg, 5.0 mol %), MesCO2H (24.6 mg, 30 mol %), K.sub.2CO.sub.3 (138 mg, 1.0 mmol) and bromobenzene (79 mg, 0.5 mmol) was stirred in dry 1,4-dioxane (2.0 ml) at 120° C. for 18 h in a nitrogen atmosphere. The reaction mixture was then diluted at 23° C. with CH.sub.2Cl.sub.2 (75 ml) and filtered through Celite and silica gel, and the filtrate was concentrated. The crude product thus obtained was purified by chromatography on silica gel (n-hexane/EtOAc/NEt.sub.3: 88/6/6). (E)-1-(Biphenyl-2-yl)-2-phenyldiazene (68 mg, 53%) was obtained as an orange viscous oil.

[0099] .sup.1H-NMR (CDCl.sub.3, 300 MHz): δ=7.81-7.75 (m, 2H), 7.62-7.35 (m, 12H). .sup.13C-NMR (CDCl.sub.3, 126 MHz): δ=152.9 (C.sub.q), 149.8 (C.sub.q), 141.2 (C.sub.q), 138.9 (C.sub.q), 131.1 (CH), 131.0 (CH), 130.9 (CH), 130.8 (CH), 129.1 (CH), 128.1 (CH), 127.7 (CH), 127.3 (CH), 123.3 (CH), 116.0 (CH). IR (neat): 3058, 3030, 1470, 1149, 1008, 770, 730, 685, 535, 497 cm.sup.−1. MS (EI) m/z (relative intensity): 258 ([M+] 42), 152 (82), 84 (100), 77 (70). HR-MS (EI) m/z calculated for C.sub.18H.sub.14N.sub.2 [M.sup.+] 258.1157, found 258.1152.

Example 14

Methyl 2′-[(E)-phenyldiazenyl]biphenyl-4-carboxylate

[0100] ##STR00014##

[0101] In an oven-dried reaction vessel, a suspension consisting of (E)-1,2-diphenyldiazene (182 mg, 1.0 mmol), [{RuCl.sub.2(p-cymene)}.sub.2] (15.3 mg, 5.0 mol %), MesCO.sub.2H (24.6 mg, 30 mol %), K.sub.2CO.sub.3 (138 mg, 1.0 mmol) and methyl 4-bromobenzoate (108 mg, 0.5 mmol) was stirred in dry 1,4-dioxane (2.0 ml) at 120° C. for 18 h in a nitrogen atmosphere. The reaction mixture was then diluted at 23° C. with CH.sub.2Cl.sub.2 (75 ml) and filtered through Celite and silica gel, and the filtrate was concentrated. The crude product thus obtained was purified by chromatography on silica gel (n-hexane/CH.sub.2Cl.sub.2: 7/3). Methyl 2′-[(E)-phenyldiazenyl]biphenyl-4-carboxylate (93 mg, 59%) was obtained as an orange solid.

[0102] M.p.=128-129° C. .sup.1H-NMR (CDCl.sub.3, 500 MHz): δ=8.09 (d, J=8.6 Hz, 2H), 7.80-7.72 (m, 3H), 7.57-7.52 (m, 4H), 7.51-7.42 (m, 4H), 3.94 (s, 3H). .sup.13C-NMR (CDCl.sub.3, 126 MHz): 8 =167.2 (C.sub.q), 152.7 (C.sub.q), 149.6 (C.sub.q), 143.7 (C.sub.q), 140.2 (C.sub.q), 131.1 (CH), 130.9 (CH), 130.9 (CH), 130.7 (CH), 129.1 (CH), 128.9 (CH), 128.8 (C.sub.q), 128.7 (CH), 123.3 (CH), 116.0 (CH), 52.1 (CH.sub.3). IR (neat): 3071, 2947, 2920, 2848, 1721, 1437, 1273, 1103, 774, 736, 686, 541 cm.sup.−1. MS (EI) m/z (relative intensity): 316 ([M.sup.+]58), 301 (100), 257 (40), 211 (44), 152 (91), 77 (94). HR-MS (El) m/z calculated for C.sub.20K.sub.16N.sub.2O.sub.2 [M.sup.+]316.1212, found 316.1205.

Example 15

Methyl 3′-methyl-2′-[(E)-(2-methylphenyl)diazenyl]biphenyl-4-carboxylate

[0103] ##STR00015##

[0104] In an oven-dried reaction vessel, a suspension consisting of (E)-1,2-di-o-tolyldiazene (210 mg, 1.0 mmol), [{RuCl.sub.2(p-cymene)}.sub.2] (15.3 mg, 5.0 mol %), MesCO.sub.2H (24.6 mg, 30 mol %), K.sub.2CO.sub.3 (138 mg, 1.0 mmol) and methyl 4-bromobenzoate (108 mg, 0.5 mmol) was stirred in dry 1,4-dioxane (2.0 ml) at 120° C. for 18 h in a nitrogen atmosphere. The reaction mixture was then diluted at 23° C. with CH.sub.2Cl.sub.2 (75 ml) and filtered through Celite and silica gel, and the filtrate was concentrated. The crude product thus obtained was purified by chromatography on silica gel (n-hexane/CH.sub.2Cl.sub.2: 7/3). Methyl 3′-methyl-2′-[(E)-(2-methylphenyl)diazenyl]biphenyl-4-carboxylate (103 mg, 60%) was obtained as an orange solid.

[0105] M.p.=123-124° C. .sup.1H-NMR (CDCl.sub.3, 500 MHz): δ=7.97 (d, J=8.1 Hz, 2H), 7.38-7.26 (m, 9H), 3.92 (s, 3H), 2.47 (s, 3H), 2.28 (s, 3H). .sup.13C-NMR (CDCl.sub.3, 126 MHz): δ=167.1 (C.sub.q), 150.9 (C.sub.q), 150.7 (C.sub.q), 145.4 (C.sub.q), 138.5 (C.sub.q), 134.7 (C.sub.q), 131.3 (CH), 131.2 (CH), 131.1 (CH), 130.8 (C.sub.q), 130.1 (CH), 129.1 (CH), 128.9 (CH), 128.1 (CH), 128.0 (C.sub.q), 126.3 (CH), 115.0 (CH), 52.0 (CH.sub.3), 19.2 (CH.sub.3), 17.1 (CH.sub.3). IR (neat): 3059, 2951, 2923, 2844, 1719, 1608, 1398, 1272, 1179, 1101, 856, 766, 739, 712 cm.sup.−1. MS (EI) m/z (relative intensity): 344 ([M.sup.+] 60), 329 (93), 285 (30), 225 (50), 165 (99), 91 (100), 65 (34). HR-MS (EI) m/z calculated for C.sub.22H.sub.20N.sub.2O.sub.2 [M.sup.+] 344.1525, found 344.1526.

Example 16

Methyl 5′-methyl-2′-[(E)-(4-methylphenyl)diazenyl]biphenyl-4-carboxylate

[0106] ##STR00016##

[0107] In an oven-dried reaction vessel, a suspension consisting of (E)-1,2-di-p-tolyldiazene (210 mg, 1.0 mmol), [{RuCl.sub.2(p-cymene)}.sub.2] (15.3 mg, 5.0 mol %), MesCO.sub.2H (24.6 mg, 30 mol %), K.sub.2CO.sub.3 (138 mg, 1.0 mmol) and methyl 4-bromobenzoate (108 mg, 0.5 mmol) was stirred in dry 1,4-dioxane (2.0 ml) at 120° C. for 18 h in a nitrogen atmosphere. The reaction mixture was then diluted at 23° C. with CH.sub.2Cl.sub.2 (75 ml) and filtered through Celite and silica gel, and the filtrate was concentrated. The crude product thus obtained was purified by chromatography on silica gel (n-hexane/CH.sub.2Cl.sub.2: 7/3). Methyl 5′-methyl-2′-[(E)-(4-methylphenyl)diazenyl]biphenyl-4-carboxylate (112 mg, 65%) was obtained as an orange solid.

[0108] M.p.=138-139° C. .sup.1H-NMR (CDCl.sub.3, 500 MHz): δ=8.08 (d, J=8.6 Hz, 2H), 7.71 (d, J=8.2 Hz, 1H), 7.64 (d, J=8.2 Hz, 2H), 7.54 (d, J=8.6 Hz, 2H), 7.37-7.35 (m, 1H), 7.27 (ddq, J=8.2, 2.0, 0.6 Hz, 1H), 7.25-7.21 (m, 2H), 3.94 (s, 3H), 2.46 (s, 3H), 2.39 (s, 3H). .sup.13C-NMR (CDCl.sub.3, 126 MHz): δ=167.2 (C.sub.q), 151.0 (C.sub.q), 147.6 (C.sub.q), 143.9 (C.sub.q), 141.4 (C.sub.q), 141.1 (C.sub.q), 140.0 (C.sub.q), 131.1 (CH), 130.8 (CH), 129.7 (CH), 129.5 (CH), 128.7 (CH), 128.6 (C.sub.q), 123.1 (CH), 115.8 (CH), 52.1 (CH.sub.3), 21.5 (CH.sub.3). IR (neat): 3029, 2948, 2921, 2844, 1721, 1599, 1437, 1274, 1149, 1112, 824, 702, 565, 385 cm.sup.−1. MS (EI) m/z (relative intensity): 344 ([M.sup.+] 66), 329 (73), 285 (29), 225 (47), 165 (86), 91 (100), 65 (25). HR-MS (ESI) m/z calculated for C.sub.22H.sub.21 N.sub.2O.sub.2 [M+H.sup.+] 345.1603, found 345.1599.

Example 17

Methyl 4′-ethyl-2′-[(E)-(3-ethylphenyl)diazenyl]biphenyl-4-carboxylate

[0109] ##STR00017##

[0110] In an oven-dried reaction vessel, a suspension consisting of (E)-1,2-bis(3-ethylphenyl)diazene (238 mg, 1.0 mmol), [{RuCl.sub.2(p-cymene)}.sub.2] (15.3 mg, 5.0 mol %), MesCO.sub.2H (24.6 mg, 30 mol %), K.sub.2CO.sub.3 (138 mg, 1.0 mmol) and methyl 4-bromobenzoate (108 mg, 0.5 mmol) was stirred in dry 1,4-dioxane (2.0 ml) at 120° C. for 18 h in a nitrogen atmosphere. The reaction mixture was then diluted at 23° C. with CH.sub.2Cl.sub.2 (75 ml) and filtered through Celite and silica gel, and the filtrate was concentrated. The crude product thus obtained was purified by chromatography on silica gel (n-hexane/CH.sub.2Cl.sub.2: 7/3). Methyl 4′-ethyl-2′-[(E)-(3-ethylphenyl)diazenyl]biphenyl-4-carboxylate (155 mg, 83%) was obtained as an orange solid. M.p.=81-82° C. .sup.1H-NMR (CDCl.sub.3, 500 MHz): δ=8.07 (d, J=8.6 Hz, 2H), 7.68-7.65 (m, 1H), 7.61-7.59 (m, 1H), 7.57-7.52 (m, 3H), 7.50 (dd, J=7.9, 0.5 Hz, 1H), 7.39 (dd, J=7.9, 1.8 Hz, 1H), 7.35 (t, J=7.7 Hz, 1H), 7.29-7.26 (m, 1H), 3.94 (s, 3H), 2.77 (q, J=7.6 Hz, 2H), 2.71 (q, J=7.6 Hz, 2H), 1.32 (t, J=7.6 Hz, 3H), 1.26 (t, J=7.6 Hz, 3H). .sup.13C-NMR (CDCl.sub.3, 126 MHz): δ=167.2 (C.sub.q), 153.0 (C.sub.q), 149.6 (C.sub.q), 145.3 (C.sub.q), 145.2 (C.sub.q), 143.8 (C.sub.q), 137.5 (C.sub.q), 130.9 (CH), 130.7 (CH), 130.6 (CH), 130.5 (CH), 129.0 (CH), 128.8 (CH), 128.6 (C.sub.q), 123.4 (CH), 119.8 (CH), 115.0 (CH), 52.1 (CH.sub.3), 28.7 (CH.sub.2), 28.7 (CH.sub.2), 15.4 (CH.sub.3), 15.3 (CH.sub.3). IR (neat): 2962, 2930, 2871, 1717, 1606, 1439, 1273, 1181, 1102, 691 cm.sup.−1. MS (El) m/z (relative intensity): 372 ([M.sup.+] 89), 357 (100), 313 (45), 239 (61), 180 (35), 165 (75), 105 (91), 77 (32). HR-MS (ESI) m/z calculated for C.sub.24H.sub.25N.sub.2O.sub.2 [M+H.sup.+] 373.1916, found 373.1915.

Example 18

Methyl 4′-isopropyl-2′-[(E)-(3-isopropylphenyl)diazenyl]biphenyl-4-carboxylate

[0111] ##STR00018##

[0112] In an oven-dried reaction vessel, a suspension consisting of (E)-1,2-bis(3-isopropylphenyl)diazene (266 mg, 1.0 mmol), [{RuCl.sub.2(p-cymene)}.sub.2] (15.3 mg, 5.0 mol %), MesCO.sub.2H (24.6 mg, 30 mol %), K.sub.2CO.sub.3 (138 mg, 1.0 mmol) and methyl 4-bromobenzoate (108 mg, 0.5 mmol) was stirred in dry 1,4-dioxane (2.0 ml) at 120° C. for 18 h in a nitrogen atmosphere. The reaction mixture was then diluted at 23° C. with CH.sub.2Cl.sub.2 (75 ml) and filtered through Celite and silica gel, and the filtrate was concentrated. The crude product thus obtained was purified by chromatography on silica gel (n-hexane/CH.sub.2Cl.sub.2: 4/6). Methyl 4′-isopropyl-2′-[(E)-(3-isopropylphenyl)diazenyl]biphenyl-4-carboxylate (160 mg, 80%) was obtained as an orange solid. M.p.=92-93° C. .sup.1H-NMR (CDCl.sub.3, 500 MHz): δ=8.07 (d, J=8.5 Hz, 2H), 7.71 (t, J=1.8 Hz, 1H), 7.63 (d, J=1.9 Hz, 1H), 7.56-7.50 (m, 4H), 7.43 (dd, J=8.0, 1.9 Hz, 1H), 7.35 (t, J=7.7 Hz, 1H), 7.32-7.29 (m, 1H), 3.93 (s, 3H), 3.04 (sept, J=6.9 Hz, 1H), 2.97 (sep, J=6.9 Hz, 1H), 1.33 (d, J=6.9 Hz, 6H), 1.27 (d, J=6.9 Hz, 6H). .sup.13C-NMR (CDCl.sub.3, 126 MHz): δ=167.2 (C.sub.q), 153.1 (C.sub.q), 150.0 (C.sub.q), 149.9 (C.sub.q), 149.5 (C.sub.q), 143.8 (C.sub.q), 137.7 (C.sub.q), 130.9 (CH), 130.6 (CH), 129.4 (CH), 129.1 (CH), 129.0 (CH), 128.8 (CH), 128.6 (C.sub.q), 122.4 (CH), 119.6 (CH), 113.7 (CH), 52.1 (CH.sub.3), 34.1 (CH), 34.0 (CH), 23.9 (CH.sub.3), 23.8 (CH.sub.3). IR (neat): 2959, 2889, 2868, 1718, 1607, 1439, 1273, 1113, 858, 835, 797, 694 cm.sup.−1. MS (EI) m/z (relative intensity): 400 ([M.sup.+] 96), 385 (100), 341 (41), 253 (45), 211 (47), 179 (43), 119 (78), 91 (42). HR-MS (EI) m/z calculated for C.sub.26H.sub.28N.sub.2O.sub.2 [M.sup.+] 400.2151, found 400.2138.

Example 19

Methyl 4′-methoxy-2′-[(E)-(3-methoxyphenyl)diazenyl]biphenyl-4-carboxylate

[0113] ##STR00019##

[0114] In an oven-dried reaction vessel, a suspension consisting of (E)-1,2-bis(3-methoxyphenyl)diazene (242 mg, 1.0 mmol), [{RuCl.sub.2(p-cymene)}.sub.2] (15.3 mg, 5.0 mol %), MesCO.sub.2H (24.6 mg, 30 mol %), K.sub.2CO.sub.3 (138 mg, 1.0 mmol) and methyl 4-bromobenzoate (108 mg, 0.5 mmol) was stirred in dry 1,4-dioxane (2.0 ml) at 120° C. for 18 h in a nitrogen atmosphere. The reaction mixture was then diluted at 23° C. with CH.sub.2Cl.sub.2 (75 ml) and filtered through Celite and silica gel, and the filtrate was concentrated. The crude product thus obtained was purified by chromatography on silica gel (n-hexane/CH.sub.2Cl.sub.2: 4/6). Methyl 4′-methoxy-2′-[(E)-(3-methoxyphenyl)diazenyl]biphenyl-4-carboxylate (139 mg, 74%) was obtained as an orange solid. M.p.=145-146° C. .sup.1H-NMR (CDCl.sub.3, 500 MHz): δ=8.06 (d, J=8.6 Hz, 2H), 7.53-7.48 (m, 3H), 7.44 (ddd, J=7.8, 1.7, 1.0 Hz, 1H), 7.37 (d, J=8.1 Hz, 1H), 7.35-7.33 (m, 1H), 7.27 (dd, J=2.6, 1.7 Hz, 1H), 7.13 (dd, J=8.5, 2.7 Hz, 1H), 7.02-6.98 (m, 1H), 3.93 (s, 3H), 3.91 (s, 3H), 3.78 (s, 3H). .sup.13C-NMR (CDCl.sub.3, 126 MHz): δ=167.1 (C.sub.q), 160.3 (C.sub.q), 160.0 (C.sub.q), 153.9 (C.sub.q), 150.0 (C.sub.q), 143.5 (C.sub.q), 133.5 (C.sub.q), 131.6 (CH), 130.9 (CH), 129.8 (CH), 128.7 (CH), 128.4 (C.sub.q), 118.4 (CH), 118.0 (CH), 117.4 (CH), 106.2 (CH), 99.3 (CH), 55.6 (CH.sub.3), 55.3 (CH.sub.3), 52.1 (CH.sub.3). IR (neat): 2950, 2902, 2834, 1719, 1597, 1519, 1481, 1433, 1270, 1132, 1103, 1039, 887, 782, 683 cm.sup.−1. MS (EI) m/z (relative intensity): 376 ([M.sup.+] 64), 361 (100), 317 (53), 241 (38), 182 (35), 139 (54), 107 (65), 77 (38). HR-MS (ESI) m/z calculated for C.sub.22H.sub.21 N.sub.2O.sub.4 [M+H.sup.+] 377.1501, found 377.1491.

Example 20

(E)-1-(3′,4′-Dichlorobiphenyl-2-yl)-2-phenyldiazene

[0115] ##STR00020##

[0116] In an oven-dried reaction vessel, a suspension consisting of (E)-1,2-diphenyldiazene (182 mg, 1.0 mmol), [{RuCl.sub.2(p-cymene)}.sub.2] (15.3 mg, 5.0 mol %), MesCO2H (24.6 mg, 30 mol %), K.sub.2CO.sub.3 (138 mg, 1.0 mmol) and 4-bromo-1,2-dichlorobenzene (113 mg, 0.5 mmol) was stirred in dry 1,4-dioxane (2.0 ml) at 120° C. for 18 h in a nitrogen atmosphere. The reaction mixture was then diluted at 23° C. with CH.sub.2Cl.sub.2 (75 ml) and filtered through Celite and silica gel, and the filtrate was concentrated. The crude product thus obtained was purified by chromatography on silica gel (n-hexane/EtOAc/NEt.sub.3: 88/6/6). (E)-1-(3′,4′-Dichlorobiphenyl-2-yl)-2-phenyldiazene (79 mg, 48%) was obtained as an orange solid.

[0117] M.p. =128-129° C. .sup.1H-NMR (CDCl.sub.3, 600 MHz): δ=7.81-7.77 (m, 3H), 7.62 (d, J=2.1 Hz, 1H), 7.54-7.52 (m, 2H), 7.51-7.45 (m, 5H), 7.29 (dd, J=8.3, 2.1 Hz, 1H). .sup.13C-NMR (CDCl.sub.3, 126 MHz): δ=152.8 (C.sub.q), 149.4 (C.sub.q), 139.0 (C.sub.q), 138.9 (C.sub.q), 132.5 (CH), 131.8 (C.sub.q), 131.6 (C.sub.q), 131.3 (CH), 131.1 (CH), 130.5 (CH), 130.3 (CH), 129.5 (CH), 129.2 (CH), 128.9 (CH), 123.3 (CH), 116.1 (CH). IR (neat): 3092, 3055, 1459, 1374, 1137, 1023, 817, 772, 755, 740, 684, 551 cm.sup.−1. MS (EI) m/z (relative intensity): 326 ([M.sup.+] 35), 221 (26), 186 (72), 151 (26), 105 (28), 77 (100), 51 (30). HR-MS (ESI) m/z calculated for C.sub.18H.sub.13Cl.sub.2N.sub.2 [M+H.sup.+] 327.0456, found 327.0451.

Example 21

(E)-1-(4′-Chloro-4-methylbiphenyl-2-yl)-2-(3-methylphenyl)diazene

[0118] ##STR00021##

[0119] In an oven-dried reaction vessel, a suspension consisting of (E)-1,2-di-m-tolyldiazene (210 mg, 1.0 mmol), [{RuCl.sub.2(p-cymene)}.sub.2] (15.3 mg, 5.0 mol %), MesCO.sub.2H (24.6 mg, 30 mol %), K.sub.2CO.sub.3 (138 mg, 1.0 mmol) and 1-bromo-4-chlorobenzene (96 mg, 0.5 mmol) was stirred in dry 1,4-dioxane (2.0 ml) at 120° C. for 18 h in a nitrogen atmosphere. The reaction mixture was then diluted at 23° C. with CH.sub.2C1.sub.2 (75 ml) and filtered through Celite and silica gel, and the filtrate was concentrated. The crude product thus obtained was purified by chromatography on silica gel (n-hexane/EtOAc/NEt.sub.3: 88/6/6). (E)-1-(4′-Chloro-4-methylbiphenyl-2-yl)-2-(3-methylphenyl)diazene (93 mg, 58%) was obtained as an orange solid.

[0120] M.p.=120-121° C. .sup.1H-NMR (CDCl.sub.3, 500 MHz): δ=7.73-7.69 (m, 1H), 7.60 (s, 1H), 7.58-7.52 (m, 2H), 7.42 (d, J=7.9 Hz, 1H), 7.38-7.36 (m, 3H), 7.36-7.32 (m, 2H), 7.29-7.25 (m, 1H), 2.45 (s, 3H), 2.41 (s, 3H). .sup.13C-NMR (CDCl.sub.3, 126 MHz): δ=152.9 (C.sub.q), 149.5 (C.sub.q), 139.0 (C.sub.q), 138.5 (C.sub.q), 137.3 (C.sub.q), 137.1 (C.sub.q), 133.2 (C.sub.q), 132.1 (CH), 131.8 (CH), 131.7 (CH), 130.4 (CH), 128.9 (CH), 127.7 (CH), 124.2 (CH), 120.0 (CH), 116.2 (CH), 21.4 (CH.sub.3), 21.2 (CH.sub.3). IR (neat): 3049, 3028, 2949, 2920, 2859, 1596, 1479, 1092, 1005, 811, 788, 747, 687 cm.sup.−1. MS (EI) m/z (relative intensity): 320 ([M.sup.+] 67), 201 (54), 166 (93), 91 (100), 65 (35). HR-MS (ESI) m/z calculated for C.sub.20H.sub.18ClN.sub.2 [M+H.sup.+] 321.1159, found 321.1141.

Example 22

(E)-1-(3′,4′-Dichloro-4-methylbiphenyl-2-yl)-2-(3-methylphenyl)diazene

[0121] ##STR00022##

[0122] In an oven-dried reaction vessel, a suspension consisting of (E)-1,2-di-m-tolyldiazene (210 mg, 1.0 mmol), [{RuCl.sub.2(p-cymene)}.sub.2] (15.3 mg, 5.0 mol %), MesCO2H (24.6 mg, 30 mol %), K.sub.2CO.sub.3 (138 mg, 1.0 mmol) and 4-bromo-1,2-dichlorobenzene (113 mg, 0.5 mmol) was stirred in dry 1,4-dioxane (2.0 ml) at 120° C. for 18 h in a nitrogen atmosphere. The reaction mixture was then diluted at 23° C. with CH.sub.2Cl.sub.2 (75 ml) and filtered through Celite and silica gel, and the filtrate was concentrated. The crude product thus obtained was purified by chromatography on silica gel (n-hexane/EtOAc/NEt.sub.3: 88/6/6). (E)-1-(3′,4′-Dichloro-4-methylbiphenyl-2-yl)-2-(3-methylphenyl)diazene (112 mg, 63%) was obtained as a pale orange solid. M.p.=127-128° C. .sup.1H-NMR (CDCl.sub.3, 500 MHz): δ=7.62-7.56 (m, 4H), 7.46 (d, J=8.3 Hz, 1H), 7.42 (d, J=7.8 Hz, 1H), 7.38-7.33 (m, 2H), 7.29-7.25 (m, 2H), 2.46 (s, 3H), 2.42 (s, 3H). .sup.13C-NMR (CDCl.sub.3, 126 MHz): δ=152.9 (C.sub.q), 149.1 (C.sub.q), 139.1 (C.sub.q), 139.0 (C.sub.q), 138.8 (C.sub.q), 136.0 (C.sub.q), 132.6 (CH), 131.9 (CH), 131.8 (CH), 131.7 (C.sub.q), 131.3 (C.sub.q), 130.2 (CH), 130.1 (CH), 129.4 (CH), 129.0 (CH), 123.7 (CH), 120.5 (CH), 116.2 (CH), 21.4 (CH.sub.3), 21.2 (CH.sub.3). IR (neat): 3026, 2918, 2858, 1601, 1463, 1371, 1133, 1027, 882, 826, 808, 686 cm.sup.-1. MS (EI) m/z (relative intensity): 354 ([M.sup.+]55), 235 (43), 200 (62), 165 (61), 91 (100), 65 (36). HR-MS (EI) m/z calculated for C.sub.20H.sub.16Cl.sub.2N.sub.2 [M.sup.+] 354.0691, found 354.0686.

Comparative Example 1

Methyl 4′-methyl-2′-[(E)-(3-methylphenyl)diazenyl]biphenyl-4-carboxylate

[0123] The experiment was carried out as described for Example 1, with the difference that N,N-dimethylformamide was used as solvent in place of 1,4-dioxane. No target product was obtained.

Comparative Example 2

Methyl 4′-methyl-2′-[(E)-(3-methylphenyl)diazenyl]biphenyl-4-carboxylate

[0124] The experiment was carried out as described for Example 1, with the difference that N,N-dimethylacetamide was used as solvent in place of 1,4-dioxane. No target product was obtained.

Comparative Example 3

Methyl 4′-methyl-2′-[(E)-(3-methylphenyl)diazenyl]biphenyl-4-carboxylate

[0125] The experiment was carried out as described for Example 1, with the difference that methanol was used as solvent in place of 1,4-dioxane. No target product was obtained.

Comparative Example 4

Methyl 4′-methyl-2′-[(E)-(3-methylphenyl)diazenyl]biphenyl-4-carboxylate

[0126] The experiment was carried out as described for Example 1, with the difference that N-methylpyrrolidone was used as solvent in place of 1,4-dioxane. No target product was obtained.

Comparative Example 5

Methyl 4′-methyl-2′-[(E)-(3-methylphenyl)diazenyl]biphenyl-4-carboxylate

[0127] The experiment was carried out as described for Example 1, with the difference that γ-valerolactone was used as solvent in place of 1,4-dioxane. No target product was obtained.

Comparative Example 6

Methyl 4′-methyl-2′-[(E)-(3-methylphenyl)diazenyl]biphenyl-4-carboxylate

[0128] The experiment was carried out as described for Example 1, with the difference that dimethyl sulphoxide was used as solvent in place of 1,4-dioxane. No target product was obtained.

Comparative Example 7

Methyl 4′-methyl-2′-[(E)-(3-methylphenyl)diazenyl]biphenyl-4-carboxylate

[0129] The experiment was carried out as described for Example 1, with the difference that water was used as solvent in place of 1,4-dioxane. No target product was obtained.

Comparative Example 8

Methyl 4′-methyl-2′-[(E)-(3-methylphenyl)diazenyl]biphenyl-4-carboxylate

[0130] The experiment was carried out as described for Example 1, with the difference that acetic acid was used as solvent in place of 1,4-dioxane. No target product was obtained.

Example 23

Methyl 2′-amino-4′-methylbiphenyl-4-carboxylate

[0131] ##STR00023##

[0132] In an oven-dried reaction vessel, a suspension consisting of (E)-1,2-di-m-tolyldiazene (421 mg, 2.0 mmol), [{RuCl.sub.2(p-cymene)}.sub.2] (30.6 mg, 5.0 mol %), MesCO2H (49.3 mg, 30 mol %), K.sub.2CO.sub.3 (276 mg, 2.0 mmol) and methyl 4-bromobenzoate (215 mg, 1.0 mmol) was stirred in dry 1,4-dioxane (3.0 ml) at 120° C. for 18 h in a nitrogen atmosphere. To the reaction mixture at 23° C. was then added [RuCl.sub.2(PPh.sub.3).sub.3] (47.9 mg, 5.0 mol %), KOH (16.8 mg, 30 mol %), Zn (262 mg, 4.0 mmol), H.sub.2O (14.4 mg, 8.0 mmol) and finally 1,4-dioxane (2.0 ml). The mixture was stirred at 80° C. for 24 h in a nitrogen atmosphere. The reaction mixture was then diluted at 23° C. with EtOAc (75 ml) and filtered through Celite and silica gel, and the filtrate was concentrated. The crude product thus obtained was purified by chromatography on silica gel (n-hexane/EtOAc: 5/1). Methyl 2′-amino-4′-methylbiphenyl-4-carboxylate (160 mg, 66%) was obtained as a white solid.

[0133] M.p.=136-137° C. .sup.1H-NMR (CDCl.sub.3, 300 MHz): δ=8.08 (d, J=8.6 Hz, 2H), 7.52 (d, J=8.6 Hz, 2H), 7.02 (d, J=7.7 Hz, 1H), 6.65 (ddd, J=7.7, 1.6, 0.7 Hz, 1H), 6.59 (s, 1H), 3.92 (s, 3H), 3.71 (s, 2H), 2.30 (s, 3H). .sup.13C-NMR (CDCl.sub.3, 400 MHz): δ=166.9 (C.sub.q), 144.5 (C.sub.q), 143.2 (C.sub.q), 139.2 (C.sub.q), 130.2 (CH), 130.0 (CH), 129.0 (CH), 128.6 (C.sub.q), 123.7 (C.sub.q), 119.8 (CH), 116.5 (CH), 52.1 (CH.sub.3), 21.2 (CH.sub.3). IR (neat): 3442, 3360, 2947, 2915, 2164, 1703, 1604, 1435, 1280, 1178, 1103, 772 cm.sup.-1. MS (EI) m/z (relative intensity): 241 ([M.sup.+] 100), 210 (31), 167 (35), 84 (24), 49 (38). HR-MS (EI) m/z calculated for C.sub.1H.sub.15NO.sub.2 [M.sup.+] 241.1103, found 241.1109.