Carbon Dioxide → 1,5-Dimethyl-3-oxabicyclo[3.2.0]heptane-2,4-dione

Participants

Reaction Steps

In a low temperature exposure unit equipped with a 125 W mercury lamp in a cooled immersion bath, stirrer and gas inlet pipe, 15 g (0.12 mole) of dimethyl maleic anhydride and 1 g (0.0054 mole) of benzophenone are dissolved in 300 ml of dichloromethane, and the solution is cooled by means of an external cooling bath with a mixture of isopropanol and dry ice to -60° to -70° C. Ethylene gas is then introduced over 1 hour and the reaction mixture is subsequently irradiated at the above temperature for 12 hours while introducing a weak flow of ethylene. The solvent is then evaporated off and the crude product is recrystallised from dichloromethane/n-hexane, affording 10 g of 1,2-dimethylcyclobutane-1,2-dicarboxylic anhydride (54% of theory) in the form of white crystals with a melting point of 84°-86° C.

Provenance & Evidence