A robust palladium(II)-Porphyrin complex as catalyst for visible light induced oxidative C-H functionalization

Abstract

A series of palladium(II)-porphyrin complexes that display dual emissions with lifetimes up to 437μs have been synthesized. Among the four complexes, PdF20TPP is an efficient and robust catalyst for photoinduced oxidative C-H functionalization by using oxygen as terminal oxidant. α-Functionalized tertiary amines were obtained in good to excellent yields by light irradiation (λ>400nm) of a mixture of PdF20TPP, tertiary amine, and nucleophile (cyanide, nitromethane, dimethyl malonate, diethyl phosphite, and acetone) under aerobic conditions. Four examples of intramolecular cyclized amine compounds could be similarly prepared. Comparison of the UV-visible absorption spectra before and after the photochemical reaction revealed that PdF20TPP was highly robust (>95 % recovery). The practical application of PdF20TPP has been revealed by the photochemical reactions performed by using a low catalyst loading (0.01mol %) and on a 10mmol scale. The PdF20TPP catalyst could sensitize photoinduced oxidation of sulfides to sulfoxides in excellent yields. Mechanistic studies revealed that the photocatalysis proceeded by singlet-oxygen oxidation. Long-lived excited states! A series of palladium(II)-porphyrin complexes have been synthesized and found to display long-lived excited states with lifetimes up to 437μs (see scheme). Among these complexes, PdF 20TPP is an efficient and robust catalyst for a broad array of photoinduced oxidative C-H functionalization reactions. PtF20TPP= platinum(II) meso-tetrakis(2,3,4,5,6-pentafluorophenyl)porphyrin.