Furan → Ethyl 7-oxabicyclo[2.2.1]hept-5-ene-2-carboxylate

Temperature

3 °C

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).

1. temperaturemaintaining the temperature at between 10° C. and 20° C
2. additionaddition
3. customthe cooling bath was removed
4. temperatureto gradually heat up during 30 min to 50° C. by exothermy
5. temperaturecooled to 40° C.
6. additiondiluted with 200 ml of dichloromethane in order
7. temperatureThe solution was subsequently cooled to room temperature
8. additionpoured on a mixture of 1.0 kg of crushed ice and 1.5 l of water
9. extractionextracted
10. extractionThe aqueous phase was extracted with 2.5 l of ethyl acetate
11. washthe combined organic phases were subsequently washed with 2.5 l of water
12. dry with materialThe organic phase was dried over sodium sulfate
13. filtrationfiltered
14. customevaporated at 45° C./1 mbar
15. customdried at 40° C./0.06 mbar for 45 min
16. customto yield
17. addition580 g (80%) of a 87:13 exo/endo mixture of product

ORD record

ord-fd9af13b2596450bbb7d0b378a54e8ab

Source dataset

uspto-grants-2002_06

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06403824B2