dimethyl 2-nitropropanedioate

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

Procedure: A solution of (3-methylbut-1-ynyl)pyridine (170 mg, 1.17 mmol), dimethyl nitromalonate (0.395 mL, 2.93 mmol), and 1-butyl-3-methylimidazolium hexafluorophosphate (0.024 mL, 0.117 mmol) in toluene (7 mL) was heated to 170° C. for 120 minutes under microwave. The reaction mixture was concentrated and purified by silica gel chromatography with hexanes/ethyl acetate (10/1) to afford methyl 4-isopropyl-5-(pyridin-2-yl)isoxazole-3-carboxylate (11 mg, 0.033 mmol, 2.8% yield). The compound had an HPLC retention time=2.96 min.—Column: YMC S5 COMBISCREEN® 4.6×50 mm; Gradient time: 4 min; Flow rate=4 ml/min; Solvent A=10% MeOH—90% Water—0.2% H3PO4; Solvent B=90% MeOH—10% water—0.2% H3PO4; Start % B=0; Final % B=100. LC-MS: M+1=247.15. 1H NMR (400 MHz, CDCl3) δ ppm 1.36 (s, 3H), 1.38 (s, 3H), 4.02 (s, 3H), 4.03-4.10 (m, 1H), 7.33-7.38 (m, 1H), 7.80-7.90 (m, 2H), and 8.72-8.76 (m, 1H). The reaction mixture was concentrated purified by silica gel chromatography with hexanes/ethyl acetate (10/1)

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

Procedure: A solution of 2-(pent-1-ynyl)pyridine (150 mg, 1.03 mmol), dimethyl nitromalonate (0.35 mL, 2.58 mmol), and 1-butyl-3-methylimidazolium hexafluorophosphate (0.021 mL, 0.103 mmol) in toluene (3 mL) was heated to 170° C. for 120 minutes under microwave. The reaction mixture was concentrated to yield a crude product which was purified by silica gel chromatography with hexanes/ethyl acetate (10/1) to afford methyl 4-propyl-5-(pyridine-2-yl)isoxazole-3-carboxylate (14.3 mg, 0.052 mmol). The compound had an HPLC retention time=3.05 min.—Column: YMC S5 COMBISCREEN® 4.6×50 mm; Gradient time: 4 min; Flow rate=4 ml/min; Solvent A=10% MeOH—90% Water—0.2% H3PO4; Solvent B=90% MeOH—10% water—0.2% H3PO4; Start % B=0; Final % B=100. LC-MS: M+1=247.1. 1H NMR (500 MHz, CDCl3) δ ppm 0.97 (t, 3H), 1.66 (sxt, J=7.48 Hz, 2H), 3.15-3.20 (m, 2H), 4.01 (s, 3H), 7.33 (ddd, J=7.56, 4.81, 1.10 Hz, 1H), 7.83 (td, J=7.77, 1.79 Hz, 1H), 7.91 (d, J=7.97 Hz, 1H), and 8.72 (d, J=4.12 Hz, 1H). The reaction mixture was concentrated to yield a crude product which was purified by silica gel chromatography with hexanes/ethyl acetate (10/1)

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

Procedure: A solution of hex-1-ynylbenzene (0.274 mL, 1.56 mmol), dimethyl 2-nitromalonate (0.421 mL, 3.12 mmol), 1-butyl-3-methylimidazoliumhexafluorophosphate (0.032 mL, 0.156 mmol) in toluene (6 mL) was subjected to the microwave at 170° C. for 150 min. The reaction mixture was concentrated under reduced pressure, and the residue was purified by flash silica gel chromatography using 5% ethyl acetate in hexane to give methyl 4-butyl-5-phenylisoxazole-3-carboxylate (0.142 g, 0.531 mmol, 34.1% yield) as a clear, colorless oil. The product was 97% pure by HPLC with a ret. time=3.11 min.−Column. CHROMOLITH® SpeedROD 4.6×50 mm (4 min.); Solvent A=10% MeOH, 90% H2O, 0.1% TFA; Solvent B=90% MeOH, 10% H2O, 0.1% TFA. LC/MS M+1=260.2. The reaction mixture was concentrated under reduced pressure the residue was purified by flash silica gel chromatography

Conditions: temp:150.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of 1,2-diphenylethyne (1.53 g, 8.6 mmol) and dimethyl 2-nitromalonate (1.05 mL, 7.83 mmol) in mesitylene (11 ml) was heated to 150° C. for 18 hr. The volatiles were removed in vacuo and the residue was chromatographed on a 5×12 cm silica gel column eluting with 0-10% EtOAc/hexanes. The essentially pure fractions containing product were concentrated to afford methyl 4,5-diphenylisoxazole-3-carboxylate (307 mg, 1.1 mmol, 14.04% yield) as a light yellow solid. HPLC retention time=1.85 minutes (YMC Combi 4.6×30 mm S-5 ODS column) eluting with 10-90% aqueous methanol+0.1 TFA a 2 minute gradient. The volatiles were removed in vacuo the residue was chromatographed on a 5×12 cm silica gel column eluting with 0-10% EtOAc/hexanes The essentially pure fractions containing product were concentrated

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

Procedure: A solution of (3,3-Dimethylbut-1-ynyl)benzene (400 mg, 2.53 mmol) and dimethyl nitromalonate (0.853 mL, 6.32 mmol) in mesitylene (5 mL) was heated at 150° C. for 48 h. The reaction mixture was concentrated, and the residue was purified by silica gel chromatography with hexanes/ethyl acetate (10/1) to yield methyl 4-tert-butyl-5-phenylisoxazole-3-carboxylate (101 mg). The compound had an HPLC ret. time=3.39 min.−Column. YMC S5 COMBISCREEN® 4.6×50 mm; Gradient time: 4 min; Flow rate=4 ml/min; Solvent A=10% MeOH−90% Water−0.2% H3PO4; Solvent B=90% MeOH−10% water−0.2% H3PO4; Start % B=0; Final % B=100. LC-MS: M+1=260+. The reaction mixture was concentrated the residue was purified by silica gel chromatography with hexanes/ethyl acetate (10/1)

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

Procedure: A solution of (cyclopropylethynyl)benzene (300 mg, 2.110 mmol) and dimethyl nitromalonate (0.854 mL, 6.33 mmol) in mesitylene (4 mL) was heated to 150° C. for 16 h. The reaction mixture was concentrated to yield a crude product which was purified by silica gel chromatography with hexanes/ethyl acetate (10/1) to yield methyl 4-cyclopropyl-5-phenylisoxazole-3-carboxylate. The compound was re-purified by preparative HPLC [Column: PHENOMENEX® S10 30×100 mm; Gradient time: 10 min; Flow rate=40 ml/min; Solvent A=10% MeOH−90% Water−0.1% TFA; Solvent B=90% MeOH−10% water−0.1% TFA; Start % B=20; Final % B=100] to yield methyl 4-cyclopropyl-5-phenylisoxazole-3-carboxylate (170 mg). The compound had an HPLC ret. time=2.77 min.−Column. YMC S5 COMBISCREEN® 4.6×50 mm; Gradient time: 4 min; Flow rate=4 ml/min; Solvent A=10% MeOH−90% Water−0.2% H3PO4; Solvent B=90% MeOH−10% water−0.2% H3PO4; Start % B=0; Final % B=100. LC-MS: M+1=244+. The reaction mixture was concentrated to yield a crude product which was purified by silica gel chromatography with hexanes/ethyl acetate (10/1)

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

Procedure: A solution of but-1-ynylbenzene (404 mg, 3.11 mmol) and dimethyl nitromalonate (0.381 mL, 2.82 mmol) in mesitylene (5 mL) was heated to 150° C. for 24 h. The reaction mixture was concentrated, and the residue purified on silica gel column with hexanes/ethyl acetate (10/1) to afford methyl 4-ethyl-5-phenylisoxazole-3-carboxylate (194 mg). The compound had an HPLC ret. time=3.25 min.−Column. YMC S5 COMBISCREEN® 4.6×50 mm; Gradient time: 4 min; Flow rate=4 ml/min; Solvent A=10% MeOH−90% Water−0.2% H3PO4; Solvent B=90% MeOH−10% water−0.2% H3PO; Start % B=0; Final % B=100. LC-MS: M+1=232+. The reaction mixture was concentrated the residue purified on silica gel column with hexanes/ethyl acetate (10/1)

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

Procedure: A solution of (4-methylpent-1-ynyl)benzene (0.247 g, 1.56 mmol), dimethyl 2-nitromalonate (0.421 mL, 3.12 mmol), 1-butyl-3-methylimidazoliumhexafluorophosphate (0.032 mL, 0.156 mmol) in toluene (5 mL) was subjected to the microwave at 170° C. for 150 min. By HPLC, the reaction was ˜40-50% complete and resubjected to the microwave conditions for 360 min. (170° C.). The toluene was decanted off leaving a dark gum which was triturated several times with ethyl acetate. The combined organic layers were concentrated under reduced pressure. The residue was purified by flash silica gel chromatography using 5% ethyl acetate in hexane to give methyl 4-isobutyl-5-phenylisoxazole-3-carboxylate (0.122 g, 0.470 mmol, 30.2% yield) as a clear, colorless oil. The compound had an HPLC ret. time=2.96 min.−Column: CHROMOLITH® SpeedROD 4.6×50 mm (4 min.); Solvent A=10% MeOH, 90% H2O, 0.1% TFA; Solvent B=90% MeOH, 10% H2O, 0.1% TFA. LC/MS M+1=259.9. 1H NMR (500 MHz, chloroform-d) δ ppm 0.88 (s, 3H), 0.89 (s, 3H), 1.89 (dt, J=13.75, 6.87 Hz, 1H), 2.80 (d, J=7.15 Hz, 2H), 4.00 (s, 3H), 7.45-7.53 (m, 3H), 7.73 (d, J=6.60 Hz, 2H). (170° C.) The toluene was decanted off leaving a dark gum which was triturated several times with ethyl acetate The combined organic layers were concentrated under reduced pressure The residue was purified by flash silica gel chromatography