tert-Butoxy and 2-furyl. Two effective substituents at stabilizing carbon-carbon double bonds

Article abstract of DOI:10.1021/jo00321a021

Potassium tert-butoxide was used as a catalyst at 25°C to establish equilibrium, approached from both sides, in two reactions of the type trans-PhCH = CHCH₂X ? trans-PhCH₂CH = CHX. At equilibrium in 80% dimethyl sulfoxide-20% tert-butyl alcohol, 4.3% trans-cinnamyl tert-butyl ether, 28.5% trans-3-phenyl-1-propenyl tert-butyl ether, and 67.2% cis-3-phenyl-1-propenyl tert-butyl ether were present. In tert-butyl alcohol, 22.4% trans-3-(2-furyl)-1-phenyl-1-propene, 72.8% trans-1-(2-furyl)-3-phenyl-1-propene, and 4.86% cis-1-(2-furyl)-3-phenyl-1-propene were present at equilibrium. These plus earlier observations show that the "double bond stabilizing abilityquot; of the tert-butoxy group is greater than that of the methoxy group and that the double bond stabilizing ability of the 2-furyl group is greater than that of the phenyl group. Reasons for these differences are discussed. In both cases steric factors are thought to be important.