Abstract
The catalytic oxidation of naphthalenes was investigated. Hydrogen peroxide (30% aqueous) was used as an oxygen source, and 2,2’-dinitro-4,4’-ditrifluoromethyldiphenyl diselenide was the oxygen-transfer catalyst. Unsubstituted naphthols produce trans-2-carboxycinnamic acid in nearly quantitative yields. Both naphthols bearing substituents on the conjugated ring deliver corresponding trans-2-carboxycinnamic acids in good to excellent yields. The 1,7- and 2,6-hydronaphthoquinones, substituted by carboxy and carboxymethyl groups, produce hydroxycinnamic acids in satisfactory to excellent yields. A catalytic domino reaction mechanism is proposed.
GRAPHICAL ABSTRACT
ACKNOWLEDGMENTS
We are grateful to Jacek Młochowski and Ludwik Syper for valuable discussions. This work was supported by the Polish State Committee for Scientific Research (Grant No. S10132/20305).
Notes
a Preparative yield. Data in parantheses refer to the yield determined by 1H NMR.
b Ref. [17]: mp 204–205 °C; ref. [46]: mp 170.5–205 °C.
c Unreacted substrate 1a was isolated in 70–95% yield.
d Yellow solid was formed.
a Preparative yield. Data in parantheses refer to the yield determined by 1H NMR.
b Mixture of polymeric 2,6-naphthoquinone was formed.
c 1.5 eq. of H2O2 was used.