Stereoselective syntheses of the 2-isopropenyl-2,3-dihydrobenzofuran nucleus: Potential chiral building blocks for the syntheses of tremetone, hydroxytremetone, and rotenone

(Chemical Equation Presented) The first enantioselective synthesis of the 2-isopropenyl-2,3-dihydrobenzofuran skeleton of tremetone and hydroxytremetone from (E)-4-(2-hydroxyphenyl)-2-methyl-2-butenyl methyl carbonate and (E)-4-(2,6-dihydroxyphenyl)-2-methyl-2-butenyl methyl carbonate, respectively, is described. The key step is a catalytic palladium-mediated reaction in the presence of the chiral Trost ligand. © 2007 American Chemical Society.