Preparation by cyclization of 1,1,3,3-tetraacetylpropene (formerly so called methenylbisacetylacetone) (SM) (m.p. 117–118°)
, ? by adding a solution of SM (1 mol) in benzene to a sodium methoxide (4 mol)
or magnesium methoxide (4 mol) solution in methanol and set aside for 24 h (quantitative yields)
; ? on heating of its potassium salt in alcoholic solution for 6–8 h at reflux. SM was prepared by treatment of ethoxymethyleneacetylacetone (m.p. 140–142°) with the potassium salt of acetylacetone in ethanol
.
