Unprecedented and Scalable Copper (I)-Catalyzed Oxidation of the Csp2-H bond on 2-phenyl-naphthalene-1,3-diol with Atmospheric Oxygen: synthesis of 2-Hydroxy-3-phenyl-1,4-naphthoquinone via direct Csp2-O bond formation

Abstract

The C_sp²-O bond formation via direct oxidation of the C_sp²-H bond on electron-rich compounds such as naphthols, is a process that generally requires drastic reaction conditions like high temperature or pressure. Addition of strong oxidants as H₂O₂, hypervalent iodine reagents (λ³ o λ⁵), expensive transition metals or rare earth elements, such as Mo, Ru Pt or Ce, is usually necessary. As part of this study on oxidative dimerization of phenols towards the total synthesis of ningalin D, 1,3-naphthalenediol was explored as starting material using stoichiometric amounts of Cu(I) and atmospheric molecular oxygen. A novel two-step sequence reaction for the formation of a 1,4-naphthoquinone was found instead of a dimerization product. The synthesis of this compound involves two consecutive oxidation processes.