Oxidative Intramolecular Coupling of 2,3-Disubstituted Phenyl Acrylic Acids and Derivatives Promoted by Di-tert-butylperoxide. -A metal-free intramolecular oxidative coupling of 2,3-disubstituted phenylacrylic acids furnishing polymethoxy--substituted phenanthrene-9-carboxylic acids (II), key intermediates for the synthesis of tylophora alkaloids, is developed. Both (E)-and (Z)-phenylacrylic acids give the phenanthrene derivatives in comparable yield. -(JI, D.-R.; YANG, H.; ZHAO, X.-J.; YANG, H.; LIU, Y.-Z.; LIAO, D.-H.; FENG, C.; ZHANG*, C.-G.; Chin. Chem. Lett. 25 (2014) 2, 348-350, http://dx.