A solution of 589 mg (2.0 mmol) of a mixture of 6-benzylidene-2,4-di-tert-butyl-cyclohexa-2,4-dienone (compound (302), Table 3) and the corresponding dimer (compound (402), Table 4), prepared according to Example 2b, in 7 ml of toluene is degassed using argon and then 58 mg (0.05 mmol) of tetrakis(triphenylphosphine)palladium(0) and 23 mg (0.20 mmol) of trifluoroacetic acid are added. The autoclave is flushed with carbon monoxide and sealed, and a carbon monoxide pressure of 5 bar is then applied. The reaction mixture is maintained at 80° C. for 20 hours. After cooling to room temperature, the reaction mixture is poured into water and extracted three times using ethyl acetate. The organic phases are combined, dried over sodium sulfate and concentrated using a vacuum rotary evaporator. Crystallisation of the residue from isopropanol yields 580 mg (90%) of 5,7-di-tert-butyl-3-phenyl-3H-benzofuran-2-one (compound (102), Table 1), m.p. 116-119° C. Analysis, calculated: C 81.95; H 8.13%. Analysis, found: C 81.93; H 8.13%.
