ACETIC ACID, 2-CYCLOBUTYLIDENE-, ETHYL ESTER

To a slurry of NaH (8.0 g, 60percent in oil) in THF (150mL), was added triethyl phosphonoacetate (44.8 g)in 25 mL of THF dropwise at 0-10 To a slurry of NaH (8.0 g, 60 in oil) in THF (150 mL) , was added triethyl phosphonoactate (44.8 g) in 25mL of THF dropwise at 0-10 over 40 min. The reaction mixture was stirred at 0-10 for another 0.5 h. Then cyclobutanone (14.0 g) in 25 mL of THF was added dropwise at 0-10 over 30 min. The reaction mixture was stirred at 0-10 for 2 h. A total of 50 mL of water was then added slowly at 20-30 . The organic solvent was removed under reduced pressure followed by addition of 150 mL of water. The aqueous solution was extracted with MTBE (3 x 100 mL) . The combined organic phase was washed with water (100 mL) . It was then dried over anhydrous MgSO(0203) Triethyl phosphonoacetate (3.32 g, 1.0 equiv) was dissolved in abs. tetrahydrofuran and added to a suspension, cooled down to 0° C., of sodium hydride (0.58 g, 1.02 equiv, 60percent dispersion) in abs. tetrahydrofuran (5 mL). The resulting reaction mixture was stirred at a temperature of 0° C. for 10 minutes and then admixed with a solution of cyclobutanone (1.0 g, 1.0 equiv) in abs. tetrahydrofuran (5 mL), and the mixture was stirred at room temperature for a further 4 h. After the cautious addition of water, the reaction mixture was concentrated under reduced pressure and admixed with dichloromethane. The aqueous phase was then repeatedly extracted with dichloromethane. The combined organic phases were dried over magnesium sulfate, filtered and concentrated under reduced pressure. By column chromatography purification of the crude product obtained (ethyl acetate/heptane gradient), ethyl cyclobutylideneacetate (1.5 g, 75percent of theory) was isolated. Ethyl cyclobutylideneacetate (1.0 g, 1.0 equiv) was dissolved in methanol and admixed with a 1 M solution of KOH in aq. methanol. The resulting reaction mixture was stirred at room temperature for 16 h, then neutralized with dil. HCl, admixed with water, concentrated under reduced pressure and then admixed with dichloromethane. The aqueous phase was then repeatedly extracted with dichloromethane. The combined organic phases were dried over magnesium sulfate, filtered and concentrated under reduced pressure. By column chromatography purification of the crude product obtained (ethyl acetate/heptane gradient), cyclobutylideneacetic acid (0.40 g, 51percent of theory) was isolated. Aniline (0.26 g, 1 equiv.) was dissolved in dichloromethane (5 mL) and cooled down to a temperature of 0° C., and diisopropylethylamine (1.98 mL, 4.0 equiv.), cyclopentylideneacetic acid (0.30 g, 1.0 equiv.) and N, N, N′, N′-tetramethyl-O-(benzotriazol-1-yl)uronium tetrafluoroborate (0.97 g, 1.1 equiv.) were added. The resulting reaction mixture was stirred at room temperature for 3 h, and water and dichloromethane were then added. The aqueous phase was then repeatedly extracted with dichloromethane. The combined organic phases were dried over magnesium sulfate, filtered and concentrated under reduced pressure. By column chromatography purification of the crude product obtained (ethyl acetate/heptane gradient), 2-cyclobutylidene-N-phenylacetamide (0.27 g, 54percent of theory) was isolated. In the next step, aluminum trichloride (0.42 g, 3.0 equiv.) was initially charged in abs. dichloroethane (5 mL) under argon in a baked-out round-bottom flask and then, while cooling with ice, a solution of 2-cyclobutylidene-N-phenylacetamide (0.20 g, 1.0 equiv.) in abs. dichloroethane (5 mL) was added. The resulting reaction mixture was stirred at room temperature for a further 4 h and then added cautiously to ice-water. After adding aqueous HCl and dichloromethane, the aqueous phase was extracted repeatedly with dichloromethane. The combined organic phases were dried over magnesium sulfate, filtered and concentrated cautiously under reduced pressure. By column chromatography purification of the crude product obtained (ethyl acetate/heptane gradient), 1′H-spiro[cyclobutyl-1, 4′-quinolin]-2′(3′H)-one was isolated as a colorless solid. 1′H-Spiro[cyclobutyl-1, 4′-quinolin]-2′(3′H)-one (0.2 g, 1 equiv.) was added to conc. acetic acid (1.5 mL) and then cautiously admixed at 0° C. with fuming nitric acid (0.5 mL). The resulting reaction mixture was then stirred at 90° C. for 2 h and, after cooling to room temperature, cautiously diluted with ice-water. The aqueous phase was then repeatedly extracted with ethyl acetate. The combined organic phases were dried over magnesium sulfate, filtered and concentrated under reduced pressure. By column chromatography purification of the crude product obtained (ethyl acetate/heptane gradient), 6′-nitro-1′H-spiro[cyclobutyl-1, 4′-quinolin]-2′(3′H)-one (100 mg, 78percent of theory) was isolated as a colorless solid. 6′-Nitro-1′H-spiro[cyclobutyl-1, 4′-quinolin]-2′(3′H)-one (100 mg, 1.0 equiv.) was dissolved under argon in abs. dioxane (2 mL) and admixed with fine cesium carbonate powder (400 mg, 3.0 equiv.). After stirring at room temperature for 5 min, cyclobutylmethyl bromide (110 mg, 2.0 equiv.) and potassium iodide (35 mg, 0.1 equiv.) were added at room temperature. The resulting reaction mixture was stirred at 150° C. under microwave conditions for 1 h and, after cooling to room temperature, water and ethyl acetate were added. The aqueous phase was then repeatedly extracted with ethyl acetate. The combined organic phases were dried over magnesium sulfate, filtered and concentrated under reduced pressure. By column chromatography purification of the crude product obtained (ethyl acetate/heptane gradient), 1-(cyclopropylmethyl)-6′-nitro-1′H-spiro[cyclobutyl-1, 4′-quinolin]-2′(3′H)-one (70 mg, 60percent of theory) was isolated as a colorless solid. In the next step, 1-(cyclopropylmethyl)-6′-nitro-1′H-spiro[cyclobutyl-1, 4′-quinolin]-2′(3′H)-one (50 g, 1 equiv.) was added together with zinc dust (55 mg, 5 equiv.) and ammonium chloride (90 mg, 10 equiv.) to methanol/water (5:1) and the mixture was stirred under argon at a temperature of 70° C. for 2 h. After cooling to room temperature, the reaction mixture was poured onto ice-water and then adjusted to pH 12 with 6 N NaOH. The aqueous phase was then repeatedly extracted with ethyl acetate. The combined organic phases were dried over magnesium sulfate, filtered and concentrated under reduced pressure. By column chromatography purification of the crude product obtained (ethyl acetate/heptane gradient), 6′-amino-1-(cyclopropylmethyl)-1′H-spiro[cyclobutyl-1, 4′-quinolin]-2′(3′H)-one (35 mg, 70percent of theory) was isolated as a colorless solid. 6′-Amino-1-(cyclopropylmethyl)-1′H-spiro[cyclobutyl-1, 4′-quinolin]-2′(3′H)-one (100 mg, 1.0 equiv.) was dissolved together with 4-methylphenylsulfonyl chloride (81 mg, 1.1 equiv) in abs. dichloromethane (5 mL) in a baked-out round-bottom flask under argon, then pyridine (0.15 mL, 5 equiv.) was added and the mixture was stirred at room temperature for 1 h. The reaction mixture was then concentrated under reduced pressure, the remaining residue was admixed with dil. HCl and dichloromethane, and the aqueous phase was extracted repeatedly with dichloromethane. The combined organic phases were dried over magnesium sulfate, filtered and concentrated under reduced pressure. By column chromatography purification of the crude product obtained (ethyl acetate/heptane gradient), 4-methyl-N-[1′-(cyclopropylmethyl)-2′-oxo-2′, 3′-dihydro-1′H-spiro[cyclobutyl-1, 4′-quinolin]-6′-yl]phenylsulfonamide (70 mg, 43percent of theory) was isolated as a colorless solid. To a stirred suspension of 60percent NaH (1.23 g, 51.35 mmol) in THF (50 mL), ethyl 2-(diethoxyphosphoryl)acetate (6.23 mL, 31.38 mmol) in 10 mL THF was added at 0°C and stirred for 5 mm at same temperature. Then cyclobutanone 75 (2 g, 28.53 mmol) in THF (10 mL) was added to it and allowed to stir at room temperature for 2h. Then the reaction mixture was quenched with cold water and extracted with ethyl acetate. The combined organic layer was dried over Na2SO4 and concentrated under reduced pressure to obtain ethyl 2-cyclobutylideneacetate 76 as colorless liquid (0.65 g, 16percent yield). 1HNMR (400 MHz, CDC13): ö 5.57 (s, 1H), 4.13 (q, 2H), 3.12 (t, 2H), 2.82 (t, 2H), 2.12-2.04 (m, 2H), 1.26 (t, 3H).Synthesis of Cyclobutylidene-acetic acid ethyl ester (2) Step A Cyclobutanone (0.5 g, 7.14 mmol) and (ethoxycarbonylmethylen)-triphenylphosphorane (2.7 g, 7.75 mmol) were heated to 125 to 140° C. in seal tube for 24 h. Reaction mixture was cooled to room temperature; 50 mL of pentane was added and stirred for 20 min. Then reaction mixture was filtered. Pentane layer was evaporated without applying pressure. Crude product was purified by column chromatography (silica gel 60-120 mesh, diethyl ether and n-pentane was used as eluent) afforded colorless oil. Yield: 0.7 g, 70percent.To a slurry of NaH (8.0 g, 60percent in oil) in THF (150mL), was added triethyl phosphonoacetate (44.8 g)in 25 mL of THF dropwise at 0-10 To a slurry of NaH (8.0 g, 60 in oil) in THF (150 mL) , was added triethyl phosphonoactate (44.8 g) in 25mL of THF dropwise at 0-10 over 40 min. The reaction mixture was stirred at 0-10 for another 0.5 h. Then cyclobutanone (14.0 g) in 25 mL of THF was added dropwise at 0-10 over 30 min. The reaction mixture was stirred at 0-10 for 2 h. A total of 50 mL of water was then added slowly at 20-30 . The organic solvent was removed under reduced pressure followed by addition of 150 mL of water. The aqueous solution was extracted with MTBE (3 x 100 mL) . The combined organic phase was washed with water (100 mL) . It was then dried over anhydrous MgSO(0203) Triethyl phosphonoacetate (3.32 g, 1.0 equiv) was dissolved in abs. tetrahydrofuran and added to a suspension, cooled down to 0° C., of sodium hydride (0.58 g, 1.02 equiv, 60percent dispersion) in abs. tetrahydrofuran (5 mL). The resulting reaction mixture was stirred at a temperature of 0° C. for 10 minutes and then admixed with a solution of cyclobutanone (1.0 g, 1.0 equiv) in abs. tetrahydrofuran (5 mL), and the mixture was stirred at room temperature for a further 4 h. After the cautious addition of water, the reaction mixture was concentrated under reduced pressure and admixed with dichloromethane. The aqueous phase was then repeatedly extracted with dichloromethane. The combined organic phases were dried over magnesium sulfate, filtered and concentrated under reduced pressure. By column chromatography purification of the crude product obtained (ethyl acetate/heptane gradient), ethyl cyclobutylideneacetate (1.5 g, 75percent of theory) was isolated. Ethyl cyclobutylideneacetate (1.0 g, 1.0 equiv) was dissolved in methanol and admixed with a 1 M solution of KOH in aq. methanol. The resulting reaction mixture was stirred at room temperature for 16 h, then neutralized with dil. HCl, admixed with water, concentrated under reduced pressure and then admixed with dichloromethane. The aqueous phase was then repeatedly extracted with dichloromethane. The combined organic phases were dried over magnesium sulfate, filtered and concentrated under reduced pressure. By column chromatography purification of the crude product obtained (ethyl acetate/heptane gradient), cyclobutylideneacetic acid (0.40 g, 51percent of theory) was isolated. Aniline (0.26 g, 1 equiv.) was dissolved in dichloromethane (5 mL) and cooled down to a temperature of 0° C., and diisopropylethylamine (1.98 mL, 4.0 equiv.), cyclopentylideneacetic acid (0.30 g, 1.0 equiv.) and N, N, N′, N′-tetramethyl-O-(benzotriazol-1-yl)uronium tetrafluoroborate (0.97 g, 1.1 equiv.) were added. The resulting reaction mixture was stirred at room temperature for 3 h, and water and dichloromethane were then added. The aqueous phase was then repeatedly extracted with dichloromethane. The combined organic phases were dried over magnesium sulfate, filtered and concentrated under reduced pressure. By column chromatography purification of the crude product obtained (ethyl acetate/heptane gradient), 2-cyclobutylidene-N-phenylacetamide (0.27 g, 54percent of theory) was isolated. In the next step, aluminum trichloride (0.42 g, 3.0 equiv.) was initially charged in abs. dichloroethane (5 mL) under argon in a baked-out round-bottom flask and then, while cooling with ice, a solution of 2-cyclobutylidene-N-phenylacetamide (0.20 g, 1.0 equiv.) in abs. dichloroethane (5 mL) was added. The resulting reaction mixture was stirred at room temperature for a further 4 h and then added cautiously to ice-water. After adding aqueous HCl and dichloromethane, the aqueous phase was extracted repeatedly with dichloromethane. The combined organic phases were dried over magnesium sulfate, filtered and concentrated cautiously under reduced pressure. By column chromatography purification of the crude product obtained (ethyl acetate/heptane gradient), 1′H-spiro[cyclobutyl-1, 4′-quinolin]-2′(3′H)-one was isolated as a colorless solid. 1′H-Spiro[cyclobutyl-1, 4′-quinolin]-2′(3′H)-one (0.2 g, 1 equiv.) was added to conc. acetic acid (1.5 mL) and then cautiously admixed at 0° C. with fuming nitric acid (0.5 mL). The resulting reaction mixture was then stirred at 90° C. for 2 h and, after cooling to room temperature, cautiously diluted with ice-water. The aqueous phase was then repeatedly extracted with ethyl acetate. The combined organic phases were dried over magnesium sulfate, filtered and concentrated under reduced pressure. By column chromatography purification of the crude product obtained (ethyl acetate/heptane gradient), 6′-nitro-1′H-spiro[cyclobutyl-1, 4′-quinolin]-2′(3′H)-one (100 mg, 78percent of theory) was isolated as a colorless solid. 6′-Nitro-1′H-spiro[cyclobutyl-1, 4′-quinolin]-2′(3′H)-one (100 mg, 1.0 equiv.) was dissolved under argon in abs. dioxane (2 mL) and admixed with fine cesium carbonate powder (400 mg, 3.0 equiv.). After stirring at room temperature for 5 min, cyclobutylmethyl bromide (110 mg, 2.0 equiv.) and potassium iodide (35 mg, 0.1 equiv.) were added at room temperature. The resulting reaction mixture was stirred at 150° C. under microwave conditions for 1 h and, after cooling to room temperature, water and ethyl acetate were added. The aqueous phase was then repeatedly extracted with ethyl acetate. The combined organic phases were dried over magnesium sulfate, filtered and concentrated under reduced pressure. By column chromatography purification of the crude product obtained (ethyl acetate/heptane gradient), 1-(cyclopropylmethyl)-6′-nitro-1′H-spiro[cyclobutyl-1, 4′-quinolin]-2′(3′H)-one (70 mg, 60percent of theory) was isolated as a colorless solid. In the next step, 1-(cyclopropylmethyl)-6′-nitro-1′H-spiro[cyclobutyl-1, 4′-quinolin]-2′(3′H)-one (50 g, 1 equiv.) was added together with zinc dust (55 mg, 5 equiv.) and ammonium chloride (90 mg, 10 equiv.) to methanol/water (5:1) and the mixture was stirred under argon at a temperature of 70° C. for 2 h. After cooling to room temperature, the reaction mixture was poured onto ice-water and then adjusted to pH 12 with 6 N NaOH. The aqueous phase was then repeatedly extracted with ethyl acetate. The combined organic phases were dried over magnesium sulfate, filtered and concentrated under reduced pressure. By column chromatography purification of the crude product obtained (ethyl acetate/heptane gradient), 6′-amino-1-(cyclopropylmethyl)-1′H-spiro[cyclobutyl-1, 4′-quinolin]-2′(3′H)-one (35 mg, 70percent of theory) was isolated as a colorless solid. 6′-Amino-1-(cyclopropylmethyl)-1′H-spiro[cyclobutyl-1, 4′-quinolin]-2′(3′H)-one (100 mg, 1.0 equiv.) was dissolved together with 4-methylphenylsulfonyl chloride (81 mg, 1.1 equiv) in abs. dichloromethane (5 mL) in a baked-out round-bottom flask under argon, then pyridine (0.15 mL, 5 equiv.) was added and the mixture was stirred at room temperature for 1 h. The reaction mixture was then concentrated under reduced pressure, the remaining residue was admixed with dil. HCl and dichloromethane, and the aqueous phase was extracted repeatedly with dichloromethane. The combined organic phases were dried over magnesium sulfate, filtered and concentrated under reduced pressure. By column chromatography purification of the crude product obtained (ethyl acetate/heptane gradient), 4-methyl-N-[1′-(cyclopropylmethyl)-2′-oxo-2′, 3′-dihydro-1′H-spiro[cyclobutyl-1, 4′-quinolin]-6′-yl]phenylsulfonamide (70 mg, 43percent of theory) was isolated as a colorless solid. To a stirred suspension of 60percent NaH (1.23 g, 51.35 mmol) in THF (50 mL), ethyl 2-(diethoxyphosphoryl)acetate (6.23 mL, 31.38 mmol) in 10 mL THF was added at 0°C and stirred for 5 mm at same temperature. Then cyclobutanone 75 (2 g, 28.53 mmol) in THF (10 mL) was added to it and allowed to stir at room temperature for 2h. Then the reaction mixture was quenched with cold water and extracted with ethyl acetate. The combined organic layer was dried over Na2SO4 and concentrated under reduced pressure to obtain ethyl 2-cyclobutylideneacetate 76 as colorless liquid (0.65 g, 16percent yield). 1HNMR (400 MHz, CDC13): ö 5.57 (s, 1H), 4.13 (q, 2H), 3.12 (t, 2H), 2.82 (t, 2H), 2.12-2.04 (m, 2H), 1.26 (t, 3H).Synthesis of Cyclobutylidene-acetic acid ethyl ester (2) Step A Cyclobutanone (0.5 g, 7.14 mmol) and (ethoxycarbonylmethylen)-triphenylphosphorane (2.7 g, 7.75 mmol) were heated to 125 to 140° C. in seal tube for 24 h. Reaction mixture was cooled to room temperature; 50 mL of pentane was added and stirred for 20 min. Then reaction mixture was filtered. Pentane layer was evaporated without applying pressure. Crude product was purified by column chromatography (silica gel 60-120 mesh, diethyl ether and n-pentane was used as eluent) afforded colorless oil. Yield: 0.7 g, 70percent.

Molecular Weight:140.18
XLogP3:1.4
Hydrogen Bond Acceptor Count:2
Rotatable Bond Count:3
Exact Mass:140.083729621
Monoisotopic Mass:140.083729621
Topological Polar Surface Area:26.3
Heavy Atom Count:10
Complexity:153
Covalently-Bonded Unit Count:1
Compound Is Canonicalized:Yes