Reaction of phosphonium ylides with 4-triphenylmethyl-1,2-benzoquinone

Article abstract of DOI:10.1016/S0040-4020(01)96274-X

The reaction of alkoxycarbonylmethylene(triphenyl)phosphoranes (4) with 4-triphenylmethyl-1,2-benzoquinone (1) in dry benzene at room temperature for 3 h led to the formation of a novel type of compounds 7 along with triphenylphosphine oxide. When compounds 7 were allowed to reflux in boiling toluene for 5 h, a mixture of 4-alkoxycarbonyl-6-triphenylmethyl-2H-1-benzopyran-2-ones (11), 5-triphenylmethyl-3-alkoxycarbonylmethylene-benzo[b]furan-2(3H)-ones (12) and triphenylphosphine were obtained. The double bond moiety of the pyrone ring in 11 was reduced with zinc dust in boiling acetic acid to form 4-alkoxycarbonyl-6-triphenylmethyl-3,4-dihydro-2H-1-benzopyran-2-ones (13) in quantitative yields. Carrying out the reduction of 11 in presence of methanol yields the succinate derivatives 14, which upon methylation with methyl iodide in dry acetone and anhydrous potassium carbonate gave the corresponding methyl ethers 15. The reaction mechanisms are considered and the structural assignments of the new compounds are based on chemical and spectroscopic evidence.