ethyl 7-oxabicyclo[2.2.1]hept-5-ene-2-carboxylate

Conditions: temp:40.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Furan (2.04 ml, 28 mmol), ethyl acrylate (2.06 ml, 20 mmol) and zinc iodide (1.92 g, 6 mmol) were placed in a sealed tube and the mixture was heated at 40° C. for 2 days. The reaction mixture was cooled to room temperature and diluted with ethyl acetate (100 ml). 10% Aqueous sodium thiosulfate solution (20 ml) was added, and the mixture was stirred at room temperature for 30 min. The organic layer was partitioned, washed with saturated brine (100 ml), and dried over anhydrous sodium sulfate. The components having a low boiling point, such as the solvent and the like, were distilled away. The obtained residue was purified by silica gel column chromatography (eluent: ethyl acetate/hexane=1/10 (volume ratio)) to give 2-ethoxycarbonyl-7-oxabicyclo[2.2.1]hept-5-ene as a mixture of exo form:endo form=7:3 (1.75 g, 10.4 mmol, yield 52.0%). The reaction mixture was cooled to room temperature The organic layer was partitioned washed with saturated brine (100 ml) dried over anhydrous sodium sulfate such as the solvent and the like, were distilled away The obtained residue was purified by silica gel column chromatography (eluent: ethyl acetate/hexane=1/10 (volume ratio))

Conditions: temp:3.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of 300 g of furan (4.32 mol) and 611 g (6.05 mol) of ethyl acrylate was cooled to 3° C. in an ice bath under an inert atmosphere. 706 g (5.2 mol) of zinc chloride were added portionwise to the solution during 30 min, maintaining the temperature at between 10° C. and 20° C. After completed addition, the cooling bath was removed and the mixture was allowed to gradually heat up during 30 min to 50° C. by exothermy. It was subsequently kept at 50° C. during 27 h by means of an oil bath, then cooled to 40° C. and diluted with 200 ml of dichloromethane in order to reduce its viscosity. The solution was subsequently cooled to room temperature, poured on a mixture of 1.0 kg of crushed ice and 1.5 l of water and extracted. The aqueous phase was extracted with 2.5 l of ethyl acetate, and the combined organic phases were subsequently washed with 2.5 l of water, a solution of 109 g sodium bicarbonate in 2.5 l water, and 250 ml of brine. The organic phase was dried over sodium sulfate, filtered, evaporated at 45° C./1 mbar and dried at 40° C./0.06 mbar for 45 min, to yield 580 g (80%) of a 87:13 exo/endo mixture of product. Purity: 98% (HPLC; ISTD). maintaining the temperature at between 10° C. and 20° C addition the cooling bath was removed to gradually heat up during 30 min to 50° C. by exothermy cooled to 40° C. diluted with 200 ml of dichloromethane in order The solution was subsequently cooled to room temperature poured on a mixture of 1.0 kg of crushed ice and 1.5 l of water extracted The aqueous phase was extracted with 2.5 l of ethyl acetate the combined organic phases were subsequently washed with 2.5 l of water The organic phase was dried over sodium sulfate filtered evaporated at 45° C./1 mbar dried at 40° C./0.06 mbar for 45 min to yield 580 g (80%) of a 87:13 exo/endo mixture of product

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

Procedure: 3.0 g (17.8 mmol) of ethyl 7-oxabicyclo[2.2.1]hept-5-en-2-carboxylate are suspended in 10 ml of water and 20 ml of ethanol. The temperature is kept below 20° C. by cooling with ice, while 3.5 g (62.3 mmol) of potassium hydroxide are added. The mixture is stirred for 2 hours at ambient temperature, the ethanol is distilled off at a bath temperature of 30° C. and the aqueous solution is extracted with ethyl acetate. The aqueous phase is acidified to a pH of 6 while cooling with ice and shaken with dichloromethane, then the combined organic extracts are dried and evaporated down. 0.8 g (32% of theory) of the title compound are obtained as a brown oil. is kept below 20° C. are added the ethanol is distilled off at a bath temperature of 30° C. the aqueous solution is extracted with ethyl acetate while cooling with ice shaken with dichloromethane the combined organic extracts are dried evaporated down

Conditions: temp:40.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Furan (2.04 ml, 28 mmol), ethyl acrylate (2.06 ml, 20 mmol) and zinc iodide (1.92 g, 6 mmol) were placed in a sealed tube and the mixture was heated at 40° C. for 2 days. The reaction mixture was cooled to room temperature and diluted with ethyl acetate (100 ml). 10% Aqueous sodium thiosulfate solution (20 ml) was added, and the mixture was stirred at room temperature for 30 min. The organic layer was partitioned, washed with saturated brine (100 ml), and dried over anhydrous sodium sulfate. The components having a low boiling point, such as the solvent and the like, were distilled away. The obtained residue was purified by silica gel column chromatography (eluent: ethyl acetate/hexane=1/10 (volume ratio)) to give 2-ethoxycarbonyl-7-oxabicyclo[2.2.1]hept-5-ene as a mixture of exo form:endo form=7:3 (1.75 g, 10.4 mmol, yield 52.0%). The reaction mixture was cooled to room temperature The organic layer was partitioned washed with saturated brine (100 ml) dried over anhydrous sodium sulfate such as the solvent and the like, were distilled away The obtained residue was purified by silica gel column chromatography (eluent: ethyl acetate/hexane=1/10 (volume ratio))