3,5-Difluoropyridine

Liquid

Preparation of 3, 5-difluoropyridine; 1000 g of dichloropyridine and 1580 g of dry potassium fluoride were initially charged in 1700 ml of sulpholane in an autoclave. Subsequently, 84 g of CNC catalyst (compound (III-1)) were added, nitrogen was injected to 3 bar and the mixture was heated to 205° C. with stirring for 48 h. During the reaction, a maximum total pressure of 12.4 bar arose. Subsequently, the mixture was cooled to 10° C. and the product was distilled off at standard pressure. After redistillation, 473 g of dichloropyridine (60percent of theory) were obtained as a colourless liquid.General procedure: To a solution of fluoroarene (0.1 M) and HSiEtGeneral procedure: To a solution of fluoroarene (0.1 M) and HSiEtGeneral procedure: An oven-dried reaction vessel (4 or 9 ml screw-cap vial) equipped with a stirring bar was allowed to cool to room temperature under vacuum. Activated 4 A molecular sieves (crushed, 50 mg), [Rh-2 ] (and solid substrates, 1.0 equiv.), were added under air. The vial was then depressurized and pressurized with argon gas three times before the addition of dry THF (1 M) (and liquid substrates, distilled over CaH2, 1.0 equiv.). Following the addition of 4, 4, 5, 5-tetramethyl-1, 3, 2-dioxaborolane (2.0-4.0 equiv. as indicated), the glass vial was placed in a 150 ml stainless-steel autoclave under an argon atmosphere. The autoclave was pressurized and depressurized with hydrogen gas three times before the indicated pressure was set. The reaction mixture was stirred at 25-40 C for 24 h. After the autoclave was carefully depressurized, trifluoroacetic anhydride (3.0 equiv.) and CH2Cl2 (0.5 ml) were added to the crude mixture and stirring was continued for 10 min at room temperature. Alternatively, di-tert-butyl dicarbonate (3.0 equiv.), triethyl amine (3.0 equiv.) and CH2Cl2 (0.5 ml) were added to the reaction mixture and stirring was continued for 2 h at room temperature. The crude was then filtered over fritted funnel and the remaining solid was washed with ethyl acetate (2x 5 ml). The combined solution was concentrated under reduced pressure and submitted to column chromatography (pentane/ethyl acetate or pentane/dichloromethane) to obtain the final product. The indicated diastereoselectivities were determined by GC analysis or from the 19F NMR spectrum immediately after the reaction. NMR yield was calculated using hexafluorobenzene (20 mul, 0.173 mmol) as internal standard.General procedure: An oven-dried reaction vessel (4 or 9 ml screw-cap vial) equipped with a stirring bar was allowed to cool to room temperature under vacuum. Activated 4 A molecular sieves (crushed, 50 mg), [Rh-2 ] (and solid substrates, 1.0 equiv.), were added under air. The vial was then depressurized and pressurized with argon gas three times before the addition of dry THF (1 M) (and liquid substrates, distilled over CaH2, 1.0 equiv.). Following the addition of 4, 4, 5, 5-tetramethyl-1, 3, 2-dioxaborolane (2.0'4.0 equiv. as indicated), the glass vial was placed in a 150 ml stainless-steel autoclave under an argon atmosphere. The autoclave was pressurized and depressurized with hydrogen gas three times before the indicated pressure was set. The reaction mixture was stirred at 25'40 °C for 24 h. After the autoclave was carefully depressurized, trifluoroacetic anhydride (3.0 equiv.) and CH2Cl2 (0.5 ml) were added to the crude mixture and stirring was continued for 10 min at room temperature. Alternatively, di-tert-butyl dicarbonate (3.0 equiv.), triethyl amine (3.0 equiv.) and CH2Cl2 (0.5 ml) were added to the reaction mixture and stirring was continued for 2 h at room temperature. The crude was then filtered over fritted funnel and the remaining solid was washed with ethyl acetate (2x 5 ml). The combined solution was concentrated under reduced pressure and submitted to column chromatography (pentane/ethyl acetate or pentane/dichloromethane) to obtain the final product. The indicated diastereoselectivities were determined by GC analysis or from the 19F NMR spectrum immediately after the reaction. NMR yield was calculated using hexafluorobenzene (20 mul, 0.173 mmol) as internal standard.

Molecular Weight:115.08
XLogP3:1.1
Hydrogen Bond Acceptor Count:3
Exact Mass:115.02335542
Monoisotopic Mass:115.02335542
Topological Polar Surface Area:12.9
Heavy Atom Count:8
Complexity:68.8
Covalently-Bonded Unit Count:1
Compound Is Canonicalized:Yes