Reaction #3166885
Related Literature (1)
openreactiondata ↗doi:10.6084/m9.figshare.5104873.v1; patent:US07132437B2
Conditions: temp:110.01; pressure:0.00; stir:; See reaction.notes.procedure_details.
Procedure: Under nitrogen, a stirred solution of 56.9 g (0.65 mol) of N-tert-butyl-N-methylamine (Fluka) and 66.1 g (0.65 mol) of triethylamine in 1 L of methylene chloride was cooled to 0° C. and treated with neat difluoroacetic anhydride [E. Sawicki, J. Org. Chem., 21, 376 (1956)] at such a rate as to maintain the reaction temperature below 10° C. The reaction was allowed to warm to ambient temperature and stir overnight. All volitiles were removed in vacuo (bath temperature<35° C.) and the residue redissolved in methylene chloride; the solution was washed with saturated sodium bicarbonate, dried (MgSO4), and concentrated to give 94 g (89%) of a yellow liquid. Vacuum distillation gave 86 g (81%) of colorless N-tert-butyl-N-methyldifluoroacetamide: bp 87–88° C. (22 mm); ′H NMR (CDCl3) δ 1.37 (s, 9H), 2.93 (t, J=3 Hz, 3H), 5.97 (t, J=57 Hz, 1H); 19F NMR. (CDCl3) δ −122.20 (d, J=57 Hz, 2F). A 17.0 g (103 mmol) sample of the amide was dissolved in 50 mL of dry THF and added slowly to a solution of 145 mmol of lithium diisopropylamine (LDA) in 450 mL of dry THF at −78° C. The reaction was allowed to stir for 1 h at −78° C. prior to the addition of 17 mL (175 mmol) of 1-iodopropane by syringe. Stirring at −78° C. was continued for 1 hr and then the reaction was allowed to warm to ambient temperature overnight. Methanol (10 mL) was added and the reaction was concentrated in vacuo; the residue was dissolved in methylene chloride and washed with 1N hydrochloric acid, dried (MgSO4) and reconcentrated to give 17.6 g (83%) of crude product. Purification by vacuum distillation gave 13.3 g (62%) of colorless N-tert-butyl-N-methyl-2,2-difluoro-valeramide: bp 125–130° C. (84 mm); ′H NMR (CDCl3) δ 0.94 (t, J=7 Hz, 3H), 1.37 (s, 9H), 1.40–1.52 (m, 2H), 1.95–2.15 (m, 2H); 19F NMR (CDCl3) δ −100.29 (t, J=20 Hz, 2F). The difluorovaleramide was dissolved in 30 mL of trifluoroacetic acid (TFA) and stirred at reflux overnight under nitrogen. The solvent was removed in vacuo and the residue dissolved in methylene chloride; the solution was washed with water, dried (MgSO4) and concentrated to give 9.7 g (100%) of crude N-methyl-2,2-difluorovaleramide: ′H NMR (CDCl3) δ 0.92 (t, J=7 Hz, 3H), 1.36–1.51 (m, 2H), 1.90–2.11 (m, 2H), 2.84 (d, J=6 Hz, 3H), 6.60–6.85 (br s, 1H); 19F NMR (CDCl3) δ −106.98 (t, J=19 Hz, 2F). The crude N-methyl amide was dissolved in 40 mL of 6N hydrochloric acid and stirred at reflux for 24 hr. The reaction was cooled to ambient temperature and extracted with methylene chloride; the extracts were combined, dried (MgSO4), and concentrated to give 8.0 g (56%) of crude 2,2-difluorovaleric acid: ′H NMR (CDCl3) δ 1.00 (t, J=7 Hz, 3H), 1.46–1.63 (m, 2H), 1.97–2.17 (m, 2H); 19F NMR (CDCl3) δ 107.16 (t, J=18 Hz, 2F). A 4.83 g (35 mmol) sample of the crude acid was dissolved in 25 mL (35.2 g, 174 mmol) of phthaloyl chloride in a flask equipped with a reflux condenser and stirred under nitrogen in a 110° C. oil bath for 6 hrs. The condenser was replaced with a distillation head and 3.22 g (60%) of colorless 2,2-difluorovaleryl chloride was collected bp 96°; ′H NMR (CDCl3) δ 1.03 (t, J=7 Hz, 3H), 1.48–1.65 (m, 2H), 2.03–2.23 (m, 2H); 19F NMR (CDCl3) δ −102.41 (t, J=18 Hz, 2F). The 2,2-difluorovaleryl chloride (20.6 mmol) was dissolved in 10 mL of methylene chloride and dropwise to a solution of 135 g (42 mmol) of anhydrous hydrazine in 20 mL of methylene chloride at 0° C. After the addition was complete, the reaction was stirred at ambient temperature for 1 h, washed with water, dried (MgSO4), and concentrated to give 3.12 g (91%) of 2,2-difluorovaleric acid hydrazide: NMR (CDCl3) δ 0.96 (t, J=7 Hz, 3H), 1.40–1.56 (m, 2H), 1.96–2.17 (m, 2H), 3.93 (br s, 2H), 7.67 (br s, 1H). A 2.84 g (18.7 mmol) sample of the crude hydrazide was dissolved in 50 mL of methanol and treated with 2.41 g (18.7 mmol) of ethyl iminovalerate. Under nitrogen, the reaction was stirred at reflux for 3 days and concentrated in vacuo. Purification by silica gel chromatography (Waters Prep-500A) using ethyl acetate/hexane (60:40) gave 3.0 g (74%) of 3-butyl-5-(1,1-difluoro)butyl-1H-1,2,4-triazole as a colorless solid: mp 92–93° C.; ′H NMR (CDCl3) δ 0.97 (t, J=Hz, 3H), 0.92 (t, J=7 Hz, 3H), 1.30–1.45 (m, 2H), 1.47–1.62 (m, 2H), 1.66–1.81 (m, 2H), 2.18–2.38 (m, 2H), 2.83 (t, J=7 Hz, 2H); 19F NMR (CDCl3) δ −97.27 (t, J=18 Hz, 2F); MS (FAB) m/e (rel intensity) 218 (100), 198 (8), 188 (5), 178 (8), 170 (5); HRMS. Calcd for M+H: 218.1469. Found: 218.1461. equipped with a reflux condenser was collected bp 96° After the addition the reaction was stirred at ambient temperature for 1 h washed with water dried (MgSO4) concentrated
Source ID: ord-a05189af9e7641eb96bf646b165f494b