ethyl 2-methyl-4-oxocyclopent-2-ene-1-carboxylate

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

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

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A round-bottom flask was charged with 10% palladium on carbon (7.6 g, 7.1 mmol). The flask was cooled to about 0° C. and EtOAc (580 mL) was added under a nitrogen atmosphere. The cooling bath was removed and ethyl 2-methyl-4-oxocyclopent-2-enecarboxylate (60.0 g, 357 mmol) was added. Hydrogen gas was bubbled through the mixture for about 5 min and the mixture was then stirred under a hydrogen atmosphere (1 atmosphere) for about 48 h. The hydrogen source was removed and the mixture was bubbled with nitrogen for about 5 min and was filtered through a pad of Celite®. The filter cake was rinsed with EtOAc (500 mL). The filtrate was concentrated under reduced pressure to give ethyl 2-methyl-4-oxocyclopentanecarboxylate (59.9 g, 99%) as a yellow liquid: 1H NMR (CDCl3) δ 4.23-4.14 (m, 2H), 3.18 (ddd, J=5.6, 6.8, 8.1 Hz, 1H), 2.73-2.65 (m, 1H), 2.60 (ddd, J=1.7, 5.5, 18.7 Hz, 1H), 2.42-2.29 (m, 2H), 2.15 (ddd, J=1.7, 7.9, 18.3 Hz, 1H), 1.29 (t, J=7.1 Hz, 3H), 1.07 (d, J=7.0 Hz, 3H). The cooling bath was removed Hydrogen gas was bubbled through the mixture for about 5 min The hydrogen source was removed the mixture was bubbled with nitrogen for about 5 min was filtered through a pad of Celite® The filter cake was rinsed with EtOAc (500 mL) The filtrate was concentrated under reduced pressure

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

Procedure: A round-bottom flask was charged with sodium 4-(ethoxycarbonyl)-2-(methoxycarbonyl)-3-methylcyclopenta-1,3-dienolate (105 g, 0.420 mol) and diglyme (1 L) to give a yellow suspension. AcOH (100 mL, 1.7 mol) was added to the resulting mixture and sodium iodide (280 g, 1.9 mol) was added portion-wise over about 5-10 min. The reaction mixture was then heated to reflux for about 3 h, cooled to room temperature, and poured over ice water (800 mL). The resulting material was extracted with Et2O (3×500 mL). The combined organic extracts were washed with brine (2×500 mL), dried over anhydrous MgSO4, and filtered. The solvent was removed under reduced pressure to give a brown liquid that was purified by vacuum distillation (80-85° C., 0.3 Torr) to give ethyl 2-methyl-4-oxocyclopent-2-enecarboxylate (40.6 g, 57%) as a yellow oil: 1H NMR (CDCl3) δ 6.06-5.98 (m, 1H), 4.30-4.11 (m, 2H), 3.72-3.65 (m, 1H), 2.77-2.66 (m, 1H), 2.66-2.57 (m, 1H), 2.17 (s, 3H), 1.30 (t, J=7.1 Hz, 3H). to give a yellow suspension was added portion-wise over about 5-10 min The reaction mixture was then heated to reflux for about 3 h The resulting material was extracted with Et2O (3×500 mL) The combined organic extracts were washed with brine (2×500 mL) dried over anhydrous MgSO4 filtered The solvent was removed under reduced pressure to give a brown liquid that was purified by vacuum distillation (80-85° C., 0.3 Torr)

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

Procedure: A round-bottom flask was charged with sodium 4-(ethoxycarbonyl)-2-(methoxycarbonyl)-3-methylcyclopenta-1,3-dienolate (105 g, 0.420 mol) and diglyme (1 L) to give a yellow suspension. AcOH (100 mL, 1.7 mol) was added to the resulting mixture and sodium iodide (280 g, 1.9 mol) was added portion-wise over about 5-10 min. The reaction mixture was then heated to reflux for about 3 h, cooled to room temperature, and poured over ice water (800 mL). The resulting material was extracted with Et2O (3×500 mL). The combined organic extracts were washed with brine (2×500 mL), dried over anhydrous MgSO4, and filtered. The solvent was removed under reduced pressure to give a brown liquid that was purified by vacuum distillation (80-85° C., 0.3 Torr) to give ethyl 2-methyl-4-oxocyclopent-2-enecarboxylate (40.6 g, 57%) as a yellow oil: 1H NMR (CDCl3) δ 6.06-5.98 (m, 1H), 4.30-4.11 (m, 2H), 3.72-3.65 (m, 1H), 2.77-2.66 (m, 1H), 2.66-2.57 (m, 1H), 2.17 (s, 3H), 1.30 (t, J=7.1 Hz, 3H). to give a yellow suspension was added portion-wise over about 5-10 min The reaction mixture was then heated to reflux for about 3 h The resulting material was extracted with Et2O (3×500 mL) The combined organic extracts were washed with brine (2×500 mL) dried over anhydrous MgSO4 filtered The solvent was removed under reduced pressure to give a brown liquid that was purified by vacuum distillation (80-85° C., 0.3 Torr)

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A round-bottom flask was charged with 10% palladium on carbon (7.6 g, 7.1 mmol). The flask was cooled to about 0° C. and EtOAc (580 mL) was added under a nitrogen atmosphere. The cooling bath was removed and ethyl 2-methyl-4-oxocyclopent-2-enecarboxylate (60.0 g, 357 mmol) was added. Hydrogen gas was bubbled through the mixture for about 5 min and the mixture was then stirred under a hydrogen atmosphere (1 atmosphere) for about 48 h. The hydrogen source was removed and the mixture was bubbled with nitrogen for about 5 min and was filtered through a pad of Celite®. The filter cake was rinsed with EtOAc (500 mL). The filtrate was concentrated under reduced pressure to give ethyl 2-methyl-4-oxocyclopentanecarboxylate (59.9 g, 99%) as a yellow liquid: 1H NMR (CDCl3) δ 4.23-4.14 (m, 2H), 3.18 (ddd, J=5.6, 6.8, 8.1 Hz, 1H), 2.73-2.65 (m, 1H), 2.60 (ddd, J=1.7, 5.5, 18.7 Hz, 1H), 2.42-2.29 (m, 2H), 2.15 (ddd, J=1.7, 7.9, 18.3 Hz, 1H), 1.29 (t, J=7.1 Hz, 3H), 1.07 (d, J=7.0 Hz, 3H). The cooling bath was removed Hydrogen gas was bubbled through the mixture for about 5 min The hydrogen source was removed the mixture was bubbled with nitrogen for about 5 min was filtered through a pad of Celite® The filter cake was rinsed with EtOAc (500 mL) The filtrate was concentrated under reduced pressure

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

Procedure: A round-bottom flask was charged with ethyl 2-methyl-4-oxocyclopent-2-enecarboxylate (2.04 g, 12.1 mmol, Preparation #CC.1), MeOH (30 mL), and cerium(III) chloride heptahydrate (5.65 g, 15.2 mmol) followed by portion-wise addition of sodium borohydride (0.574 g, 15.2 mmol). The suspension was stirred at room temperature over about 16 h. Saturated aqueous NH4Cl solution (50 mL) was added. The mixture was stirred for about 10 min and Et2O (60 mL) was added. The layers were separated and the aqueous layer was extracted with Et2O (3×30 mL). The combined organic layers were washed with saturated aqueous NaHCO3, dried over anhydrous MgSO4, filtered, and concentrated to dryness under reduced pressure. The residue was purified via silica gel chromatography eluting with 20-60% EtOAc/pentane to yield cis-ethyl 4-hydroxy-2-methylcyclopent-2-enecarboxylate (0.96 g, 46%): 1H NMR (400 MHz, CDCl3) δ 5.77-5.71 (m, 1H), 4.63 (m, 1H), 4.28-4.11 (m, 2H), 3.27-3.20 (m, 1H), 2.59 (bs, 1H), 2.41-2.30 (m, 1H), 2.00 (d, J=14.2 Hz, 1H), 1.79 (d, =1.2 Hz, 3H), 1.30 (t, J=7.1 Hz, 3H) and trans-ethyl 4-hydroxy-2-methylcyclopent-2-enecarboxylate (0.69 g, 33%): 1H NMR (400 MHz, CDCl3) δ 5.63 (dd, J=1.8, 3.4 Hz, 1H), 4.98 (m, 1H), 4.20-4.11 (m, 2H), 3.60-3.53 (m, 1H), 2.57 (ddd, J=4.4, 7.1, 13.9 Hz, 1H), 1.98 (ddd, J=3.5, 8.4, 13.9 Hz, 1H), 1.80 (d, J=1.4, 3H), 1.46 (bs, 1H), 1.27 (t, J=7.1 Hz, 3H). The mixture was stirred for about 10 min The layers were separated the aqueous layer was extracted with Et2O (3×30 mL) The combined organic layers were washed with saturated aqueous NaHCO3 dried over anhydrous MgSO4 filtered concentrated to dryness under reduced pressure The residue was purified via silica gel chromatography eluting with 20-60% EtOAc/pentane

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

Procedure: A round-bottom flask was charged with ethyl 2-methyl-4-oxocyclopent-2-enecarboxylate (2.04 g, 12.1 mmol, Preparation #CC.1), MeOH (30 mL), and cerium(III) chloride heptahydrate (5.65 g, 15.2 mmol) followed by portion-wise addition of sodium borohydride (0.574 g, 15.2 mmol). The suspension was stirred at room temperature over about 16 h. Saturated aqueous NH4Cl solution (50 mL) was added. The mixture was stirred for about 10 min and Et2O (60 mL) was added. The layers were separated and the aqueous layer was extracted with Et2O (3×30 mL). The combined organic layers were washed with saturated aqueous NaHCO3, dried over anhydrous MgSO4, filtered, and concentrated to dryness under reduced pressure. The residue was purified via silica gel chromatography eluting with 20-60% EtOAc/pentane to yield cis-ethyl 4-hydroxy-2-methylcyclopent-2-enecarboxylate (0.96 g, 46%): 1H NMR (400 MHz, CDCl3) δ 5.77-5.71 (m, 1H), 4.63 (m, 1H), 4.28-4.11 (m, 2H), 3.27-3.20 (m, 1H), 2.59 (bs, 1H), 2.41-2.30 (m, 1H), 2.00 (d, J=14.2 Hz, 1H), 1.79 (d, =1.2 Hz, 3H), 1.30 (t, J=7.1 Hz, 3H) and trans-ethyl 4-hydroxy-2-methylcyclopent-2-enecarboxylate (0.69 g, 33%): 1H NMR (400 MHz, CDCl3) δ 5.63 (dd, J=1.8, 3.4 Hz, 1H), 4.98 (m, 1H), 4.20-4.11 (m, 2H), 3.60-3.53 (m, 1H), 2.57 (ddd, J=4.4, 7.1, 13.9 Hz, 1H), 1.98 (ddd, J=3.5, 8.4, 13.9 Hz, 1H), 1.80 (d, J=1.4, 3H), 1.46 (bs, 1H), 1.27 (t, J=7.1 Hz, 3H). The mixture was stirred for about 10 min The layers were separated the aqueous layer was extracted with Et2O (3×30 mL) The combined organic layers were washed with saturated aqueous NaHCO3 dried over anhydrous MgSO4 filtered concentrated to dryness under reduced pressure The residue was purified via silica gel chromatography eluting with 20-60% EtOAc/pentane

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

Procedure: In a 1 L round-bottomed flask jacketed flask, copper(I) chloride (0.736 g, 7.43 mmol), (S)-(−)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (4.63 g, 7.43 mmol), and sodium tert-butoxide (0.714 g, 7.43 mmol) in toluene (250 mL) were added to give a yellow solution. The mixture was stirred at ambient temperature for about 15 min. after which the solution became brown. The solution was cooled to about 5° C. and polymethylhydrosiloxane (14.86 mL, 223 mmol) was added and the solution was stirred at about 5° C. for about 40 min. The solution was cooled to about −15° C. and a solution of ethyl 2-methyl-4-oxocyclopent-2-enecarboxylate (25.00 g, 149 mmol) and tert-butyl alcohol (61.7 mL, 654 mmol) in toluene (250 mL) was added in one portion. The reaction stirred at −15° C. for 144 h. The reaction mixture was quenched by the addition of 1:1 ethanol/toluene (350 mL) and Celite® 545 (25 g). The mixture was stirred and allowed to warm to ambient temperature. The reaction mixture was concd in vacuo, chasing with heptane. Heptane (350 mL) was added to the residue and solids were removed by filtration. The filtrate was concd in vacuo and the crude product was purified by silica gel chromatography using a gradient of 10 to 50% EtOAc in heptane over 7 column volumes to give ethyl 2-methyl-4-oxocyclopentanecarboxylate (scalemic mixture of diastereomers), predominantly (1S,2R)-ethyl 2-methyl-4-oxocyclopentanecarboxylate (11.2 g, 42% yield) as a colorless oil. 1H NMR (400 MHz, CDCl3) δ 4.19 (qd, J=7.1, 0.6, 2H), 3.17 (ddd, J=8.1, 6.8, 5.6, 1H), 2.76-2.56 (m, 2H), 2.67-2.46 (m, 2H), 2.43-2.29 (m, 2H), 2.16 (ddd, J=18.3, 7.8, 1.7, 1H), 1.29 (t, J=7.2, 3H), 1.06 (d, J=7.0, 3H). In a 1 L round-bottomed flask jacketed to give a yellow solution The solution was cooled to about 5° C. the solution was stirred at about 5° C. for about 40 min The solution was cooled to about −15° C. The reaction stirred at −15° C. for 144 h The reaction mixture was quenched by the addition of 1:1 ethanol/toluene (350 mL) and Celite® 545 (25 g) The mixture was stirred to warm to ambient temperature Heptane (350 mL) was added to the residue and solids were removed by filtration the crude product was purified by silica gel chromatography

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

Procedure: In a 5 L round bottom flask, sodium 4-(ethoxycarbonyl)-2-(methoxycarbonyl)-3-methylcyclo-penta-1,3-dienolate (485 g, 1954 mmol), KCl (204 g, 2736 mmol, JT Baker), and AcOH (392 mL, 6839 mmol, JT Baker) in toluene (1200 mL) and water (1200 mL) were heated at reflux for about 6 h. The reaction mixture was allowed to cool to ambient temperature for about 16 h. The reaction mixture was then poured into a 12 L flask and diluted with water (3 L). Solid NaHCO3 (450 g, 5.3 mol) was added cautiously portionwise with stirring over about 1 h. After about an additional 30 min of stirring, the basic aqueous phase was separated and further extracted with Et2O (4×400 mL). The combined organic layers were washed with water (4×500 mL) and brine (500 mL), dried over anhydrous MgSO4, filtered, and concd under reduced pressure to yield a yellow oil that was purified by vacuum distillation (92-94° C., 0.4 mmHg) to give ethyl 2-methyl-4-oxocyclopent-2-enecarboxylate (229 g, 69%) as a yellow oil: 1H NMR (CDCl3) δ 6.04-6.01 (m, 1H), 4.26-4.17 (m, 2H), 3.67 (m, 1H), 2.72 (m, 1H), 2.62 (m, 1H), 2.16 (s, 3H), 1.32-1.27 (t, J=7.1 Hz, 3H). at reflux for about 6 h The reaction mixture was then poured into a 12 L flask After about an additional 30 min of stirring the basic aqueous phase was separated further extracted with Et2O (4×400 mL) The combined organic layers were washed with water (4×500 mL) and brine (500 mL) dried over anhydrous MgSO4 filtered concd under reduced pressure to yield a yellow oil that was purified by vacuum distillation (92-94° C., 0.4 mmHg)

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

Procedure: In a 1 L round bottom flask jacketed flask, copper(I) chloride (0.736 g, 7.43 mmol), (S)-(−)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (4.63 g, 7.43 mmol), and sodium tert-butoxide (0.714 g, 7.43 mmol) in toluene (250 mL) were added to give a yellow solution. The mixture was stirred at ambient temperature for about 15 min. after which the solution became brown. The solution was cooled to about 5° C. and polymethylhydrosiloxane (14.86 mL, 223 mmol) was added and the solution was stirred at about 5° C. for about 40 min. The solution was cooled to about −15° C. and a solution of ethyl 2-methyl-4-oxocyclopent-2-enecarboxylate (25.00 g, 149 mmol) and tert-butyl alcohol (61.7 mL, 654 mmol) in toluene (250 mL) was added in one portion. The reaction was stirred at −15° C. for 144 h. The reaction mixture was quenched by the addition of 1:1 ethanol/toluene (350 mL) and Celite® 545 (25 g). The mixture was stirred and allowed to warm to ambient temperature. The reaction mixture was concd in vacuo, chasing with heptane. Heptane (350 mL) was added to the residue and solids were removed by filtration. The filtrate was concd in vacuo and the crude product was purified by silica gel chromatography using a gradient of 10 to 50% EtOAc in heptane over 7 column volumes to give ethyl 2-methyl-4-oxocyclopentanecarboxylate (scalemic mixture of diastereomers), predominantly (1S,2R)-ethyl 2-methyl-4-oxocyclopentanecarboxylate (11.2 g, 42% yield) as a colorless oil. 1H NMR (400 MHz, CDCl3) δ 4.19 (qd, J=7.1, 0.6, 2H), 3.17 (ddd, J=8.1, 6.8, 5.6, 1H), 2.76-2.56 (m, 2H), 2.67-2.46 (m, 2H), 2.43-2.29 (m, 2H), 2.16 (ddd, J=18.3, 7.8, 1.7, 1H), 1.29 (t, J=7.2, 3H), 1.06 (d, J=7.0, 3H). In a 1 L round bottom flask jacketed to give a yellow solution The solution was cooled to about 5° C. the solution was stirred at about 5° C. for about 40 min The solution was cooled to about −15° C. The reaction was stirred at −15° C. for 144 h The reaction mixture was quenched by the addition of 1:1 ethanol/toluene (350 mL) and Celite® 545 (25 g) The mixture was stirred to warm to ambient temperature Heptane (350 mL) was added to the residue and solids were removed by filtration the crude product was purified by silica gel chromatography

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

Procedure: In a 5 L round bottom flask, sodium 4-(ethoxycarbonyl)-2-(methoxycarbonyl)-3-methylcyclo-penta-1,3-dienolate (485 g, 1954 mmol), KCl (204 g, 2736 mmol, JT Baker), and AcOH (392 mL, 6839 mmol, JT Baker) in toluene (1200 mL) and water (1200 mL) were heated at reflux for about 6 h. The reaction mixture was allowed to cool to ambient temperature for about 16 h. The reaction mixture was then poured into a 12 L flask and diluted with water (3 L). Solid NaHCO3 (450 g, 5.3 mol) was added cautiously portionwise with stirring over about 1 h. After about an additional 30 min of stirring, the basic aqueous phase was separated and further extracted with Et2O (4×400 mL). The combined organic layers were washed with water (4×500 mL) and brine (500 mL), dried over anhydrous MgSO4, filtered, and concd under reduced pressure to yield a yellow oil that was purified by vacuum distillation (92-94° C., 0.4 mmHg) to give ethyl 2-methyl-4-oxocyclopent-2-enecarboxylate (229 g, 69%) as a yellow oil: 1H NMR (CDCl3) δ 6.04-6.01 (m, 1H), 4.26-4.17 (m, 2H), 3.67 (m, 1H), 2.72 (m, 1H), 2.62 (m, 1H), 2.16 (s, 3H), 1.32-1.27 (t, J=7.1 Hz, 3H). at reflux for about 6 h The reaction mixture was then poured into a 12 L flask After about an additional 30 min of stirring the basic aqueous phase was separated further extracted with Et2O (4×400 mL) The combined organic layers were washed with water (4×500 mL) and brine (500 mL) dried over anhydrous MgSO4 filtered concd under reduced pressure to yield a yellow oil that was purified by vacuum distillation (92-94° C., 0.4 mmHg)