ethyl 2,3-dihydro-1,4-benzodioxine-3-carboxylate

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

Procedure: Under a nitrogen atmosphere, add 18.2 g (131 mmol) of dry potassium carbonate and 13 g (50 mmol) of ethyl 2,3-dibromopropionate in succession to a solution of 20 g (18 1 mmol) of catechol dissolved in 120 cm3 of anhydrous acetone. The operation is repeated four times in succession at intervals of 15 minutes. The reaction mixture is heated at reflux for 18 hours, and then cooled and filtered through Celite. The filtrate is concentrated to a residual volume of 60 cm3, then hydrolysed with 80 cm3 of water and extracted with diethyl ether. After drying over magnesium sulfate, the ethereal phase is concentrated under reduced pressure and the crude product is purified by distillation under reduced pressure (b.p.=155° C. under 15 mm Hg). Ethyl 2,3-dihydro-1,4-benzodioxin-2-carboxylate is thereby obtained in a yield of 80%. nD25 =1.5214 ##STR25## at intervals of 15 minutes The reaction mixture is heated at reflux for 18 hours cooled filtered through Celite The filtrate is concentrated to a residual volume of 60 cm3 hydrolysed with 80 cm3 of water and extracted with diethyl ether After drying over magnesium sulfate the ethereal phase is concentrated under reduced pressure the crude product is purified by distillation under reduced pressure (b.p.=155° C. under 15 mm Hg)

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

Procedure: 26 g (100 mmol) of ethyl 2,3-dibromopropionate and 36.4 g (264 mmol) of anhydrous potassium carbonate are added to 40 g (181 mmol) of catechol dissolved in 200 ml of anhydrous acetone. The operation is repeated 4 times within one hour; the reaction mixture is then heated to boiling. After 18 hours at reflux under argon, the mixture is cooled and then filtered over Celite. After concentration of the filtrate in vacuo, the residue is hydrolysed and then the aqueous phase is extracted with ether. The organic phase is dried over magnesium sulphate and then concentrated in vacuo. The title ester is obtained pure by distillation under reduced pressure (15 mm Hg; b.p.=155° C.). within one hour the reaction mixture is then heated to boiling After 18 hours at reflux under argon the mixture is cooled filtered over Celite the aqueous phase is extracted with ether The organic phase is dried over magnesium sulphate concentrated in vacuo

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

Procedure: 26 g (100 mmol) of ethyl 2,3-dibromopropionate and 36.4 g (264 mmol) of anhydrous potassium carbonate are added to 40 g (181 mmol) of catechol dissolved in 200 ml of anhydrous acetone. The operation is repeated 4 times within one hour; the reaction mixture is then heated to boiling. After 18 hours at reflux under argon, the mixture is cooled and then filtered over Celite. After concentration of the filtrate in vacuo, the residue is hydrolysed and then the aqueous phase is extracted with ether. The organic phase is dried over magnesium sulphate and then concentrated in vacuo. The title ester is obtained pure by distillation under reduced pressure (15 mm Hg; b.p.=155° C.). within one hour the reaction mixture is then heated to boiling After 18 hours at reflux under argon the mixture is cooled filtered over Celite the aqueous phase is extracted with ether The organic phase is dried over magnesium sulphate concentrated in vacuo

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

Procedure: 26 g (100 mmol) of ethyl 2,3-dibromopropionate and 36.4 g (264 mmol) of anhydrous potassium carbonate are added to 40 g (181 mmol) of catechol dissolved in 200 ml of anhydrous acetone. The operation is repeated 4 times within one hour; the reaction mixture is then heated to boiling. After 18 hours at reflux under argon, the mixture is cooled and then filtered over Celite. After concentration of the filtrate in vacuo, the residue is hydrolysed and then the aqueous phase is extracted with ether. The organic phase is dried over magnesium sulphate and then concentrated in vacuo. The title ester is obtained pure by distillation under reduced pressure (15 mm Hg; b.p.=155° C.). within one hour the reaction mixture is then heated to boiling After 18 hours at reflux under argon the mixture is cooled filtered over Celite the aqueous phase is extracted with ether The organic phase is dried over magnesium sulphate concentrated in vacuo

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

Procedure: Under a nitrogen atmosphere, add 18.2 g (131 mmol) of dry potassium carbonate and 13 g (50 mmol) of ethyl 2,3-dibromopropionate in succession to a solution of 20 g (18 1 mmol) of catechol dissolved in 120 cm3 of anhydrous acetone. The operation is repeated four times in succession at intervals of 15 minutes. The reaction mixture is heated at reflux for 18 hours, and then cooled and filtered through Celite. The filtrate is concentrated to a residual volume of 60 cm3, then hydrolysed with 80 cm3 of water and extracted with diethyl ether. After drying over magnesium sulfate, the ethereal phase is concentrated under reduced pressure and the crude product is purified by distillation under reduced pressure (b.p.=155° C. under 15 mm Hg). Ethyl 2,3-dihydro-1,4-benzodioxin-2-carboxylate is thereby obtained in a yield of 80%. nD25 =1.5214 ##STR25## at intervals of 15 minutes The reaction mixture is heated at reflux for 18 hours cooled filtered through Celite The filtrate is concentrated to a residual volume of 60 cm3 hydrolysed with 80 cm3 of water and extracted with diethyl ether After drying over magnesium sulfate the ethereal phase is concentrated under reduced pressure the crude product is purified by distillation under reduced pressure (b.p.=155° C. under 15 mm Hg)

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

Procedure: Under a nitrogen atmosphere, add 18.2 g (131 mmol) of dry potassium carbonate and 13 g (50 mmol) of ethyl 2,3-dibromopropionate in succession to a solution of 20 g (18 1 mmol) of catechol dissolved in 120 cm3 of anhydrous acetone. The operation is repeated four times in succession at intervals of 15 minutes. The reaction mixture is heated at reflux for 18 hours, and then cooled and filtered through Celite. The filtrate is concentrated to a residual volume of 60 cm3, then hydrolysed with 80 cm3 of water and extracted with diethyl ether. After drying over magnesium sulfate, the ethereal phase is concentrated under reduced pressure and the crude product is purified by distillation under reduced pressure (b.p.=155° C. under 15 mm Hg). Ethyl 2,3-dihydro-1,4-benzodioxin-2-carboxylate is thereby obtained in a yield of 80%. nD25 =1.5214 ##STR25## at intervals of 15 minutes The reaction mixture is heated at reflux for 18 hours cooled filtered through Celite The filtrate is concentrated to a residual volume of 60 cm3 hydrolysed with 80 cm3 of water and extracted with diethyl ether After drying over magnesium sulfate the ethereal phase is concentrated under reduced pressure the crude product is purified by distillation under reduced pressure (b.p.=155° C. under 15 mm Hg)

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

Procedure: Under a nitrogen atmosphere, add 18.2 g (131 mmol) of dry potassium carbonate and 13 g (50 mmol) of ethyl 2,3-dibromopropionate in succession to a solution of 20 g (181 mmol) of catechol dissolved in 120 cm3 of anhydrous acetone. The operation is repeated four times in succession at intervals of 15 minutes. The reaction mixture is heated at reflux for 18 hours, and then cooled and filtered through Celite. The filtrate is concentrated to a residual volume of 60 cm3, then hydrolysed with 80 cm3 of water and extracted with diethyl ether. After drying over magnesium sulfate, the ethereal phase is concentrated under reduced pressure and the crude product is purified by distillation under reduced pressure (b.p.=155° C. under 15 mm Hg). Ethyl 2,3-dihydro-1,4-benzodioxin-2-carboxylate is thereby obtained in a yield of 80%. nD25 =1.5214 ##STR27## at intervals of 15 minutes The reaction mixture is heated at reflux for 18 hours cooled filtered through Celite The filtrate is concentrated to a residual volume of 60 cm3 hydrolysed with 80 cm3 of water and extracted with diethyl ether After drying over magnesium sulfate the ethereal phase is concentrated under reduced pressure the crude product is purified by distillation under reduced pressure (b.p.=155° C. under 15 mm Hg)

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

Procedure: 26 g (100 mmol) of ethyl 2,3-dibromopropionate and 36.4 g (264 mmol) of anhydrous potassium carbonate are added to 40 g (181 mmol) of catechol dissolved in 200 ml of anhydrous acetone. The operation is repeated 4 times within one hour; the reaction mixture is then heated to boiling. After 18 hours at reflux under argon, the mixture is cooled and then filtered over Celite. After concentration of the filtrate in vacuo, the residue is hydrolysed and then the aqueous phase is extracted with ether. The organic phase is dried over magnesium sulphate and then concentrated in vacuo. The title ester is obtained pure by distillation under reduced pressure (15 mm Hg; b.p.=155° C.). within one hour the reaction mixture is then heated to boiling After 18 hours at reflux under argon the mixture is cooled filtered over Celite the aqueous phase is extracted with ether The organic phase is dried over magnesium sulphate concentrated in vacuo

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

Procedure: 26 g (100 mmol) of ethyl 2,3-dibromopropionate and 36.4 g (264 mmol) of anhydrous potassium carbonate are added to 40 g (181 mmol) of catechol dissolved in 200 ml of anhydrous acetone. The operation is repeated 4 times within one hour; the reaction mixture is then heated to boiling. After 18 hours at reflux under argon, the mixture is cooled and then filtered over Celite. After concentration of the filtrate in vacuo, the residue is hydrolysed and then the aqueous phase is extracted with ether. The organic phase is dried over magnesium sulphate and then concentrated in vacuo. The title ester is obtained pure by distillation under reduced pressure (15 mm Hg; b.p.=155° C.). within one hour the reaction mixture is then heated to boiling After 18 hours at reflux under argon the mixture is cooled filtered over Celite the aqueous phase is extracted with ether The organic phase is dried over magnesium sulphate concentrated in vacuo