ethyl 4-(2-ethoxy-2-oxoethyl)sulfanylbutanoate

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

Procedure: Sodium metal (4.3 g, 0.18 mol) was added cautiously in small portions to ethanol (150 mL). After the sodium completely dissolved, the mixture was cooled to 0° C. and ethyl 2-sulfanylacetate (21.9 g, 0.18 mol), was added. Ethyl 4-chlorobutanoate (27.4 g, 0.18 mol) was then added slowly and the resulting mixture stirred overnight at rt. The solid was filtered off, and then the filtrate concentrated under reduced pressure. The oil obtained was partitioned between water and ethyl acetate. The organic layer was collected, dried over anhydrous Na2SO4 and concentrated under vacuum to give the desired ethyl 4-((ethoxycarbonyl)methylthio)butanoate (40.2 g, 95%) as colorless oil. The crude material was used without further purification in the follow step. The solid was filtered off the filtrate concentrated under reduced pressure The oil obtained was partitioned between water and ethyl acetate The organic layer was collected dried over anhydrous Na2SO4 concentrated under vacuum

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

Procedure: Sodium metal (4.3 g, 0.18 mol) was added cautiously in small portions to ethanol (150 mL). After the sodium completely dissolved, the mixture was cooled to 0° C. and ethyl 2-sulfanylacetate (21.9 g, 0.18 mol), was added. Ethyl 4-chlorobutanoate (27.4 g, 0.18 mol) was then added slowly and the resulting mixture stirred overnight at rt. The solid was filtered off, and then the filtrate concentrated under reduced pressure. The oil obtained was partitioned between water and ethyl acetate. The organic layer was collected, dried over anhydrous Na2SO4 and concentrated under vacuum to give the desired ethyl 4-((ethoxycarbonyl)methylthio)butanoate (40.2 g, 95%) as colorless oil. The crude material was used without further purification in the follow step. The solid was filtered off the filtrate concentrated under reduced pressure The oil obtained was partitioned between water and ethyl acetate The organic layer was collected dried over anhydrous Na2SO4 concentrated under vacuum

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

Procedure: To a solution of 5 g (219 mmol) of sodium in 13 mL of anhydrous EtOH and 88 mL of ether are added dropwise, at 0° C. and under argon, 20.5 g (87.5 mmol) of ethyl 4-[(2-ethoxy-2-oxoethyl)sulfanyl]butanoate. After stirring for 18 hours at room temperature, the reaction mixture is poured into a mixture of AcOH (12 mL)/ice (70 g). The medium is then concentrated under reduced pressure, and the residue obtained is taken up in 100 mL of ether, washed with brine (2×50 mL), dried over Na2SO4, filtered and concentrated under reduced pressure. The residue obtained is purified by chromatography on silica gel, eluting with a cyclohexane/EtOAc gradient of from 0 to 10% EtOAc. 5.64 g of ethyl 3-oxotetrahydro-2H-thiopyrane-2-carboxylate are obtained in the form of a yellow oil. The medium is then concentrated under reduced pressure the residue obtained washed with brine (2×50 mL) dried over Na2SO4 filtered concentrated under reduced pressure The residue obtained is purified by chromatography on silica gel eluting with a cyclohexane/EtOAc gradient of from 0 to 10% EtOAc

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

Procedure: To a solution of 5 g (219 mmol) of sodium in 13 mL of anhydrous EtOH and 88 mL of ether are added dropwise, at 0° C. and under argon, 20.5 g (87.5 mmol) of ethyl 4-[(2-ethoxy-2-oxoethyl)sulfanyl]butanoate. After stirring for 18 hours at room temperature, the reaction mixture is poured into a mixture of AcOH (12 mL)/ice (70 g). The medium is then concentrated under reduced pressure, and the residue obtained is taken up in 100 mL of ether, washed with brine (2×50 mL), dried over Na2SO4, filtered and concentrated under reduced pressure. The residue obtained is purified by chromatography on silica gel, eluting with a cyclohexane/EtOAc gradient of from 0 to 10% EtOAc. 5.64 g of ethyl 3-oxotetrahydro-2H-thiopyrane-2-carboxylate are obtained in the form of a yellow oil. The medium is then concentrated under reduced pressure the residue obtained washed with brine (2×50 mL) dried over Na2SO4 filtered concentrated under reduced pressure The residue obtained is purified by chromatography on silica gel eluting with a cyclohexane/EtOAc gradient of from 0 to 10% EtOAc

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

Procedure: To a solution of 5 g (219 mmol) of sodium in 13 mL of anhydrous EtOH and 88 mL of ether are added dropwise, at 0° C. and under argon, 20.5 g (87.5 mmol) of ethyl 4-[(2-ethoxy-2-oxoethyl)sulfanyl]butanoate. After stirring for 18 hours at room temperature, the reaction mixture is poured into a mixture of AcOH (12 mL)/ice (70 g). The medium is then concentrated under reduced pressure, and the residue obtained is taken up in 100 mL of ether, washed with brine (2×50 mL), dried over Na2SO4, filtered and concentrated under reduced pressure. The residue obtained is purified by chromatography on silica gel, eluting with a cyclohexane/EtOAc gradient of from 0 to 10% EtOAc. 5.64 g of ethyl 3-oxotetrahydro-2H-thiopyrane-2-carboxylate are obtained in the form of a yellow oil. The medium is then concentrated under reduced pressure the residue obtained washed with brine (2×50 mL) dried over Na2SO4 filtered concentrated under reduced pressure The residue obtained is purified by chromatography on silica gel eluting with a cyclohexane/EtOAc gradient of from 0 to 10% EtOAc

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

Procedure: Sodium metal (4.3 g, 0.18 mol) was added cautiously in small portions to ethanol (150 mL). After the sodium completely dissolved, the mixture was cooled to 0° C. and ethyl 2-sulfanylacetate (21.9 g, 0.18 mol), was added. Ethyl 4-chlorobutanoate (27.4 g, 0.18 mol) was then added slowly and the resulting mixture stirred overnight at rt. The solid was filtered off, and then the filtrate concentrated under reduced pressure. The oil obtained was partitioned between water and ethyl acetate. The organic layer was collected, dried over anhydrous Na2SO4 and concentrated under vacuum to give the desired ethyl 4-((ethoxycarbonyl)methylthio)butanoate (40.2 g, 95%) as colorless oil. The crude material was used without further purification in the follow step. The solid was filtered off the filtrate concentrated under reduced pressure The oil obtained was partitioned between water and ethyl acetate The organic layer was collected dried over anhydrous Na2SO4 concentrated under vacuum