6-bromo-2,3-difluorobenzaldehyde

Conditions: temp:22.01; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 2-bromo-5,6-difluorobenzaldehyde is reacted with 4-pentylphenylboronic acid in the presence of a Pd catalyst to give 3,4-difluoro-4′-pentylbiphenyl-2-carbaldehyde. This compound is reacted with trimethylsulfonium iodide, to give 3,4-difluoro-2-(oxiran-2-yl)-4′-pentyl-biphenyl. Without further purification, this compound is converted into 1,2-difluoro-7-pentylphenanthrene in the presence of BF3 etherate. The raw product is purified by the procedure typical for this type of liquid-crystal materials (cf. DE-A 195 00 768), yielding 1,2-difluoro-7-pentylphenanthrene in the form of colorless crystals. Kumar, J. Org. Chem. 1997, 62, 8535-8539 discloses the coupling of boronic acid compounds with a bromo compound having aldehyde functionality.

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A solution of 152 mmol of 2,2,6,6-tetramethylpiperidine and 152 mmol of n-butyllithium (1.6 M solution in n-hexane) in 280 ml of dry tetrahydrofuran is admixed with 145 mmol of 1-bromo-3,4-difluorobenzene at −75° C. This temperature is maintained for 4 hours, and then 174 mmol of DMF are added dropwise. The reaction mixture is then slowly thawed, hydrolyzed with water at −20° C., acidified using hydrochloric acid and extracted with tert-butyl methyl ether. The combined organic extracts are washed with saturated sodium chloride solution and dried using sodium sulfate. The solvent is removed under reduced pressure, and the raw product is purified by chromatography over silica gel (eluent: dichloromethane/n-heptane 1:1) and recrystallization from n-heptane, yielding 18 g (56%) of 2-bromo-5,6-difluorobenzaldehyde in the form of slightly yellow crystals.—M.p.: 40-43.5° C.—1H-NMR (400 MHz, CDCl3/TMS): δ=10.31 (dd, 4J(HF)=2 Hz, 5J(HF)=1.5 Hz, 1 H, CHO), 7.45 (ddd, 3J(HH)=9 Hz, 4J(HF)=4 Hz, 5J(HF)=2 Hz, 1 H, Har), 7.28 (ddd, 3J(HH)=9 Hz, 3J(HF)=9 Hz, 4J(HF)=8 Hz, 1 H, Har).—19F-NMR (376.5 MHz, 1H broad-band decoupled, CDCl3/CFCl3): δ=−136.4 (d, 3J=19.2 Hz), −139.2 (d, 3J=19.2 Hz). This temperature is maintained for 4 hours extracted with tert-butyl methyl ether The combined organic extracts are washed with saturated sodium chloride solution dried The solvent is removed under reduced pressure the raw product is purified by chromatography over silica gel (eluent: dichloromethane/n-heptane 1:1) and recrystallization from n-heptane

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A solution of 152 mmol of 2,2,6,6-tetramethylpiperidine and 152 mmol of n-butyllithium (1.6 M solution in n-hexane) in 280 ml of dry tetrahydrofuran is admixed with 145 mmol of 1-bromo-3,4-difluorobenzene at −75° C. This temperature is maintained for 4 hours, and then 174 mmol of DMF are added dropwise. The reaction mixture is then slowly thawed, hydrolyzed with water at −20° C., acidified using hydrochloric acid and extracted with tert-butyl methyl ether. The combined organic extracts are washed with saturated sodium chloride solution and dried using sodium sulfate. The solvent is removed under reduced pressure, and the raw product is purified by chromatography over silica gel (eluent: dichloromethane/n-heptane 1:1) and recrystallization from n-heptane, yielding 18 g (56%) of 2-bromo-5,6-difluorobenzaldehyde in the form of slightly yellow crystals.—M.p.: 40-43.5° C.—1H-NMR (400 MHz, CDCl3/TMS): δ=10.31 (dd, 4J(HF)=2 Hz, 5J(HF)=1.5 Hz, 1 H, CHO), 7.45 (ddd, 3J(HH)=9 Hz, 4J(HF)=4 Hz, 5J(HF)=2 Hz, 1 H, Har), 7.28 (ddd, 3J(HH)=9 Hz, 3J(HF)=9 Hz, 4J(HF)=8 Hz, 1 H, Har).—19F-NMR (376.5 MHz, 1H broad-band decoupled, CDCl3/CFCl3): δ=−136.4 (d, 3J=19.2 Hz), −139.2 (d, 3J=19.2 Hz). This temperature is maintained for 4 hours extracted with tert-butyl methyl ether The combined organic extracts are washed with saturated sodium chloride solution dried The solvent is removed under reduced pressure the raw product is purified by chromatography over silica gel (eluent: dichloromethane/n-heptane 1:1) and recrystallization from n-heptane

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: In a similar manner to Example 9 Method A, 1-(7-fluorobenzo[b]thiophen-4-yl)propan-1-one was prepared starting from 4-bromo-1,2-difluorobenzene (39.7 g). This was lithiated and reacted with dimethylformamide to give 6-bromo-2,3-difluorobenzaldehyde (41.3 g) as a yellow solid. The aldehyde was reacted with methyl thioglycolate (14.6 ml) to give methyl 4-bromo-7-fluorobenzo[b]thiophene-2-carboxylate (31.2 g) as a yellow solid. The ester was hydrolysed to give 4-bromo-7-fluorobenzo[b]thiophene-2-carboxylic acid (37.25 g) as a yellow solid which was decarboxylated using copper and quinoline at 170-180° C. for 4 hours to give 4-bromo-7-fluorobenzo[b]thiophene (18.2 g) as a white solid, m.p. 47-48° C. This compound (7.4 g) was reacted with magnesium (0.85 g) and then with N-methoxy-N-methylpropionamide (5.6 g) to give 1-(7-fluorobenzo[b]thiophen-4-yl)propan-1-one (2.1 g) as an oil which was used without further purification.

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: In a similar manner to Example 9 Method A, 1-(7-fluorobenzo[b]thiophen-4-yl)propan-1-one was prepared starting from 4-bromo-1,2-difluorobenzene (39.7 g). This was lithiated and reacted with dimethylformamide to give 6-bromo-2,3-difluorobenzaldehyde (41.3 g) as a yellow solid. The aldehyde was reacted with methyl thioglycolate (14.6 ml) to give methyl 4-bromo-7-fluorobenzo[b]thiophene-2-carboxylate (31.2 g) as a yellow solid. The ester was hydrolysed to give 4-bromo-7-fluorobenzo[b]thiophene-2-carboxylic acid (37.25 g) as a yellow solid which was decarboxylated using copper and quinoline at 170-180° C. for 4 hours to give 4-bromo-7-fluorobenzo[b]thiophene (18.2 g) as a white solid, m.p. 47-48° C. This compound (7.4 g) was reacted with magnesium (0.85 g) and then with N-methoxy-N-methylpropionamide (5.6 g) to give 1-(7-fluorobenzo[b]thiophen-4-yl)propan-1-one (2.1 g) as an oil which was used without further purification.