ethyl 2-methyl-4-oxocyclopentane-1-carboxylate

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

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

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 ethyl 2-methyl-4-oxocyclopentanecarboxylate (10.0 g, 58.8 mmol) and DCE (180 mL). The solution was cooled to about 0° C. and AcOH (5.7 mL, 100 mmol) and dibenzylamine (11.3 mL, 58.8 mmol) were added drop-wise, resulting in formation of a thick suspension. The reaction mixture was warmed to about 10° C. and sodium triacetoxyborohydride (21.2 g, 100 mmol) was added portion-wise and the reaction mixture was stirred at room temperature for about 20 h. The reaction mixture was slowly poured into stirred saturated aqueous NaHCO3 (300 mL) for about 20 min. The layers were separated and the aqueous phase was extracted with DCM (3×100 mL). The combined organic extracts were washed with brine (2×100 mL), dried over anhydrous Na2SO4, and concentrated to dryness under reduced pressure. The crude yellow oil was purified via flash column chromatography eluting with a gradient of 0-30% EtOAc in heptane. The solvent was removed under reduced pressure to give ethyl 4-(dibenzylamino)-2-methylcyclopentanecarboxylate (15.5 g, 75%) as colorless oil: 1H NMR (pyridine-d5) δ 7.53 (dd, J=0.9, 7.9 Hz, 4H), 7.43-7.35 (m, 4H), 7.33-7.25 (m, 2H), 4.22-4.06 (m, 2H), 3.79 (d, J=14.2 Hz, 2H), 3.70 (d, J=14.2 Hz, 2H), 3.34-3.22 (m, 1H), 2.76 (dd, J=7.9, 16.6 Hz, 1H), 2.25-2.13 (m, 1H), 2.09-1.94 (m, 2H), 1.88-1.79 (m, 1H), 1.52 (dd, J=10.5, 22.5 Hz, 1H), 1.16 (t, J=7.1 Hz, 3H), 0.98 (d, J=7.0 Hz, 3H). resulting in formation of a thick suspension The reaction mixture was warmed to about 10° C. The reaction mixture was slowly poured The layers were separated the aqueous phase was extracted with DCM (3×100 mL) The combined organic extracts were washed with brine (2×100 mL) dried over anhydrous Na2SO4 concentrated to dryness under reduced pressure The crude yellow oil was purified via flash column chromatography eluting with a gradient of 0-30% EtOAc in heptane The solvent was removed under reduced pressure

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

Procedure: A round-bottom flask was charged with ethyl 2-methyl-4-oxocyclopentanecarboxylate (10.0 g, 58.8 mmol) and DCE (180 mL). The solution was cooled to about 0° C. and AcOH (5.7 mL, 100 mmol) and dibenzylamine (11.3 mL, 58.8 mmol) were added drop-wise, resulting in formation of a thick suspension. The reaction mixture was warmed to about 10° C. and sodium triacetoxyborohydride (21.2 g, 100 mmol) was added portion-wise and the reaction mixture was stirred at room temperature for about 20 h. The reaction mixture was slowly poured into stirred saturated aqueous NaHCO3 (300 mL) for about 20 min. The layers were separated and the aqueous phase was extracted with DCM (3×100 mL). The combined organic extracts were washed with brine (2×100 mL), dried over anhydrous Na2SO4, and concentrated to dryness under reduced pressure. The crude yellow oil was purified via flash column chromatography eluting with a gradient of 0-30% EtOAc in heptane. The solvent was removed under reduced pressure to give ethyl 4-(dibenzylamino)-2-methylcyclopentanecarboxylate (15.5 g, 75%) as colorless oil: 1H NMR (pyridine-d5) δ 7.53 (dd, J=0.9, 7.9 Hz, 4H), 7.43-7.35 (m, 4H), 7.33-7.25 (m, 2H), 4.22-4.06 (m, 2H), 3.79 (d, J=14.2 Hz, 2H), 3.70 (d, J=14.2 Hz, 2H), 3.34-3.22 (m, 1H), 2.76 (dd, J=7.9, 16.6 Hz, 1H), 2.25-2.13 (m, 1H), 2.09-1.94 (m, 2H), 1.88-1.79 (m, 1H), 1.52 (dd, J=10.5, 22.5 Hz, 1H), 1.16 (t, J=7.1 Hz, 3H), 0.98 (d, J=7.0 Hz, 3H). resulting in formation of a thick suspension The reaction mixture was warmed to about 10° C. The reaction mixture was slowly poured The layers were separated the aqueous phase was extracted with DCM (3×100 mL) The combined organic extracts were washed with brine (2×100 mL) dried over anhydrous Na2SO4 concentrated to dryness under reduced pressure The crude yellow oil was purified via flash column chromatography eluting with a gradient of 0-30% EtOAc in heptane The solvent was removed under reduced pressure

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

Procedure: A round-bottom flask was charged with ethyl 2-methyl-4-oxocyclopentanecarboxylate (10.0 g, 58.8 mmol) and DCE (180 mL). The solution was cooled to about 0° C. and AcOH (5.7 mL, 100 mmol) and dibenzylamine (11.3 mL, 58.8 mmol) were added drop-wise, resulting in formation of a thick suspension. The reaction mixture was warmed to about 10° C. and sodium triacetoxyborohydride (21.2 g, 100 mmol) was added portion-wise and the reaction mixture was stirred at room temperature for about 20 h. The reaction mixture was slowly poured into stirred saturated aqueous NaHCO3 (300 mL) for about 20 min. The layers were separated and the aqueous phase was extracted with DCM (3×100 mL). The combined organic extracts were washed with brine (2×100 mL), dried over anhydrous Na2SO4, and concentrated to dryness under reduced pressure. The crude yellow oil was purified via flash column chromatography eluting with a gradient of 0-30% EtOAc in heptane. The solvent was removed under reduced pressure to give ethyl 4-(dibenzylamino)-2-methylcyclopentanecarboxylate (15.5 g, 75%) as colorless oil: 1H NMR (pyridine-d5) δ 7.53 (dd, J=0.9, 7.9 Hz, 4H), 7.43-7.35 (m, 4H), 7.33-7.25 (m, 2H), 4.22-4.06 (m, 2H), 3.79 (d, J=14.2 Hz, 2H), 3.70 (d, J=14.2 Hz, 2H), 3.34-3.22 (m, 1H), 2.76 (dd, J=7.9, 16.6 Hz, 1H), 2.25-2.13 (m, 1H), 2.09-1.94 (m, 2H), 1.88-1.79 (m, 1H), 1.52 (dd, J=10.5, 22.5 Hz, 1H), 1.16 (t, J=7.1 Hz, 3H), 0.98 (d, J=7.0 Hz, 3H). resulting in formation of a thick suspension The reaction mixture was warmed to about 10° C. The reaction mixture was slowly poured The layers were separated the aqueous phase was extracted with DCM (3×100 mL) The combined organic extracts were washed with brine (2×100 mL) dried over anhydrous Na2SO4 concentrated to dryness under reduced pressure The crude yellow oil was purified via flash column chromatography eluting with a gradient of 0-30% EtOAc in heptane The solvent was removed under reduced pressure

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

Procedure: A round bottom flask was charged with ethyl 2-methyl-4-oxocyclopentanecarboxylate (10.0 g, 58.8 mmol) and DCE (180 mL). The solution was cooled to about 0° C. and AcOH (5.7 mL, 100 mmol) and dibenzylamine (11.3 mL, 58.8 mmol) were added dropwise, resulting in formation of a thick suspension. The reaction mixture was warmed to about 10° C. and sodium triacetoxyborohydride (21.2 g, 100 mmol) was added portionwise. The reaction mixture was stirred at ambient temperature for about 20 h then slowly poured into stirred saturated aqueous NaHCO3 (300 mL) and stirred for about 20 min. The layers were separated and the aqueous phase was extracted with DCM (3×100 mL). The combined organic extracts were washed with brine (2×100 mL), dried over anhydrous Na2SO4, and concd under reduced pressure. The crude yellow oil was purified via silica gel chromatography eluting with a gradient of 0-30% EtOAc in heptane to give ethyl 4-(dibenzylamino)-2-methylcyclopentanecarboxylate (scalemic mixture of diastereomers), predominantly (1S,2R,4S) ethyl 4-(dibenzylamino)-2-methylcyclopentanecarboxylate (15.5 g, 75%) as a colorless oil: 1H NMR (pyridine-d5) δ 7.53 (dd, J=0.9, 7.9 Hz, 4H), 7.43-7.35 (m, 4H), 7.33-7.25 (m, 2H), 4.22-4.06 (m, 2H), 3.79 (d, J=14.2 Hz, 2H), 3.70 (d, J=14.2 Hz, 2H), 3.34-3.22 (m, 1H), 2.76 (dd, J=7.9, 16.6 Hz, 1H), 2.25-2.13 (m, 1H), 2.09-1.94 (m, 2H), 1.88-1.79 (m, 1H), 1.52 (dd, J=10.5, 22.5 Hz, 1H), 1.16 (t, J=7.1 Hz, 3H), 0.98 (d, J=7.0 Hz, 3H). resulting in formation of a thick suspension The reaction mixture was warmed to about 10° C. then slowly poured stirred for about 20 min The layers were separated the aqueous phase was extracted with DCM (3×100 mL) The combined organic extracts were washed with brine (2×100 mL) dried over anhydrous Na2SO4, and concd under reduced pressure The crude yellow oil was purified via silica gel chromatography eluting with a gradient of 0-30% EtOAc in heptane

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

Procedure: A round bottom flask was charged with ethyl 2-methyl-4-oxocyclopentanecarboxylate (10.0 g, 58.8 mmol) and DCE (180 mL). The solution was cooled to about 0° C. and AcOH (5.7 mL, 100 mmol) and dibenzylamine (11.3 mL, 58.8 mmol) were added dropwise, resulting in formation of a thick suspension. The reaction mixture was warmed to about 10° C. and sodium triacetoxyborohydride (21.2 g, 100 mmol) was added portionwise. The reaction mixture was stirred at ambient temperature for about 20 h then slowly poured into stirred saturated aqueous NaHCO3 (300 mL) and stirred for about 20 min. The layers were separated and the aqueous phase was extracted with DCM (3×100 mL). The combined organic extracts were washed with brine (2×100 mL), dried over anhydrous Na2SO4, and concd under reduced pressure. The crude yellow oil was purified via silica gel chromatography eluting with a gradient of 0-30% EtOAc in heptane to give ethyl 4-(dibenzylamino)-2-methylcyclopentanecarboxylate (scalemic mixture of diastereomer), predominantly (1S,2R,4S)-ethyl 4-(dibenzylamino)-2-methylcyclopentanecarboxylate) (15.5 g, 75%) as a colorless oil: 1H NMR (pyridine-d5) δ 7.53 (dd, J=0.9, 7.9 Hz, 4H), 7.43-7.35 (m, 4H), 7.33-7.25 (m, 2H), 4.22-4.06 (m, 2H), 3.79 (d, J=14.2 Hz, 2H), 3.70 (d, J=14.2 Hz, 2H), 3.34-3.22 (m, 1H), 2.76 (dd, J=7.9, 16.6 Hz, 1H), 2.25-2.13 (m, 1H), 2.09-1.94 (m, 2H), 1.88-1.79 (m, 1H), 1.52 (dd, J=10.5, 22.5 Hz, 1H), 1.16 (t, J=7.1 Hz, 3H), 0.98 (d, J=7.0 Hz, 3H). resulting in formation of a thick suspension The reaction mixture was warmed to about 10° C. then slowly poured stirred for about 20 min The layers were separated the aqueous phase was extracted with DCM (3×100 mL) The combined organic extracts were washed with brine (2×100 mL) dried over anhydrous Na2SO4, and concd under reduced pressure The crude yellow oil was purified via silica gel chromatography eluting with a gradient of 0-30% EtOAc in heptane